feat(core): add built-in converter provider

crates/owlry-core/src/providers/converter/currency.rs

@@ -0,0 +1,313 @@
+use std::collections::HashMap;
+use std::fs;
+use std::path::PathBuf;
+use std::sync::Mutex;
+use std::time::SystemTime;
+
+use serde::{Deserialize, Serialize};
+
+const ECB_URL: &str = "https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml";
+const CACHE_MAX_AGE_SECS: u64 = 86400; // 24 hours
+
+static CACHED_RATES: Mutex<Option<CurrencyRates>> = Mutex::new(None);
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CurrencyRates {
+    pub date: String,
+    pub rates: HashMap<String, f64>,
+}
+
+struct CurrencyAlias {
+    code: &'static str,
+    aliases: &'static [&'static str],
+}
+
+static CURRENCY_ALIASES: &[CurrencyAlias] = &[
+    CurrencyAlias {
+        code: "EUR",
+        aliases: &["eur", "euro", "euros", "€"],
+    },
+    CurrencyAlias {
+        code: "USD",
+        aliases: &["usd", "dollar", "dollars", "$", "us_dollar"],
+    },
+    CurrencyAlias {
+        code: "GBP",
+        aliases: &["gbp", "pound_sterling", "£", "british_pound", "pounds"],
+    },
+    CurrencyAlias {
+        code: "JPY",
+        aliases: &["jpy", "yen", "¥", "japanese_yen"],
+    },
+    CurrencyAlias {
+        code: "CHF",
+        aliases: &["chf", "swiss_franc", "francs"],
+    },
+    CurrencyAlias {
+        code: "CAD",
+        aliases: &["cad", "canadian_dollar", "c$"],
+    },
+    CurrencyAlias {
+        code: "AUD",
+        aliases: &["aud", "australian_dollar", "a$"],
+    },
+    CurrencyAlias {
+        code: "CNY",
+        aliases: &["cny", "yuan", "renminbi", "rmb"],
+    },
+    CurrencyAlias {
+        code: "SEK",
+        aliases: &["sek", "swedish_krona", "kronor"],
+    },
+    CurrencyAlias {
+        code: "NOK",
+        aliases: &["nok", "norwegian_krone"],
+    },
+    CurrencyAlias {
+        code: "DKK",
+        aliases: &["dkk", "danish_krone"],
+    },
+    CurrencyAlias {
+        code: "PLN",
+        aliases: &["pln", "zloty", "złoty"],
+    },
+    CurrencyAlias {
+        code: "CZK",
+        aliases: &["czk", "czech_koruna"],
+    },
+    CurrencyAlias {
+        code: "HUF",
+        aliases: &["huf", "forint"],
+    },
+    CurrencyAlias {
+        code: "TRY",
+        aliases: &["try", "turkish_lira", "lira"],
+    },
+];
+
+pub fn resolve_currency_code(alias: &str) -> Option<&'static str> {
+    let lower = alias.to_lowercase();
+
+    // Check aliases
+    for ca in CURRENCY_ALIASES {
+        if ca.aliases.contains(&lower.as_str()) {
+            return Some(ca.code); // ca.code is already &'static str
+        }
+    }
+
+    // Check if it's a raw 3-letter ISO code we know about
+    let upper = alias.to_uppercase();
+    if upper.len() == 3 {
+        if upper == "EUR" {
+            return Some("EUR");
+        }
+        if let Some(rates) = get_rates()
+            && rates.rates.contains_key(&upper)
+        {
+            for ca in CURRENCY_ALIASES {
+                if ca.code == upper {
+                    return Some(ca.code);
+                }
+            }
+        }
+    }
+
+    None
+}
+
+#[allow(dead_code)]
+pub fn is_currency_alias(alias: &str) -> bool {
+    resolve_currency_code(alias).is_some()
+}
+
+pub fn get_rates() -> Option<CurrencyRates> {
+    // Check memory cache first
+    {
+        let cache = CACHED_RATES.lock().ok()?;
+        if let Some(ref rates) = *cache {
+            return Some(rates.clone());
+        }
+    }
+
+    // Try disk cache
+    if let Some(rates) = load_cache()
+        && !is_stale(&rates)
+    {
+        let mut cache = CACHED_RATES.lock().ok()?;
+        *cache = Some(rates.clone());
+        return Some(rates);
+    }
+
+    // Fetch fresh rates
+    if let Some(rates) = fetch_rates() {
+        save_cache(&rates);
+        let mut cache = CACHED_RATES.lock().ok()?;
+        *cache = Some(rates.clone());
+        return Some(rates);
+    }
+
+    // Fall back to stale cache
+    load_cache()
+}
+
+fn cache_path() -> Option<PathBuf> {
+    let cache_dir = dirs::cache_dir()?.join("owlry");
+    Some(cache_dir.join("ecb_rates.json"))
+}
+
+fn load_cache() -> Option<CurrencyRates> {
+    let path = cache_path()?;
+    let content = fs::read_to_string(path).ok()?;
+    serde_json::from_str(&content).ok()
+}
+
+fn save_cache(rates: &CurrencyRates) {
+    if let Some(path) = cache_path() {
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent).ok();
+        }
+        if let Ok(json) = serde_json::to_string_pretty(rates) {
+            fs::write(path, json).ok();
+        }
+    }
+}
+
+fn is_stale(_rates: &CurrencyRates) -> bool {
+    let path = match cache_path() {
+        Some(p) => p,
+        None => return true,
+    };
+    let metadata = match fs::metadata(path) {
+        Ok(m) => m,
+        Err(_) => return true,
+    };
+    let modified = match metadata.modified() {
+        Ok(t) => t,
+        Err(_) => return true,
+    };
+    match SystemTime::now().duration_since(modified) {
+        Ok(age) => age.as_secs() > CACHE_MAX_AGE_SECS,
+        Err(_) => true,
+    }
+}
+
+fn fetch_rates() -> Option<CurrencyRates> {
+    let response = reqwest::blocking::get(ECB_URL).ok()?;
+    let body = response.text().ok()?;
+    parse_ecb_xml(&body)
+}
+
+fn parse_ecb_xml(xml: &str) -> Option<CurrencyRates> {
+    let mut rates = HashMap::new();
+    let mut date = String::new();
+
+    for line in xml.lines() {
+        let trimmed = line.trim();
+
+        // Extract date: <Cube time='2026-03-26'>
+        if trimmed.contains("time=")
+            && let Some(start) = trimmed.find("time='")
+        {
+            let rest = &trimmed[start + 6..];
+            if let Some(end) = rest.find('\'') {
+                date = rest[..end].to_string();
+            }
+        }
+
+        // Extract rate: <Cube currency='USD' rate='1.0832'/>
+        if trimmed.contains("currency=") && trimmed.contains("rate=") {
+            let currency = extract_attr(trimmed, "currency")?;
+            let rate_str = extract_attr(trimmed, "rate")?;
+            let rate: f64 = rate_str.parse().ok()?;
+            rates.insert(currency, rate);
+        }
+    }
+
+    if rates.is_empty() {
+        return None;
+    }
+
+    Some(CurrencyRates { date, rates })
+}
+
+fn extract_attr(line: &str, attr: &str) -> Option<String> {
+    let needle = format!("{}='", attr);
+    let start = line.find(&needle)? + needle.len();
+    let rest = &line[start..];
+    let end = rest.find('\'')?;
+    Some(rest[..end].to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_resolve_currency_code_iso() {
+        assert_eq!(resolve_currency_code("usd"), Some("USD"));
+        assert_eq!(resolve_currency_code("EUR"), Some("EUR"));
+    }
+
+    #[test]
+    fn test_resolve_currency_code_name() {
+        assert_eq!(resolve_currency_code("dollar"), Some("USD"));
+        assert_eq!(resolve_currency_code("euro"), Some("EUR"));
+        assert_eq!(resolve_currency_code("pounds"), Some("GBP"));
+    }
+
+    #[test]
+    fn test_resolve_currency_code_symbol() {
+        assert_eq!(resolve_currency_code("$"), Some("USD"));
+        assert_eq!(resolve_currency_code("€"), Some("EUR"));
+        assert_eq!(resolve_currency_code("£"), Some("GBP"));
+    }
+
+    #[test]
+    fn test_resolve_currency_unknown() {
+        assert_eq!(resolve_currency_code("xyz"), None);
+    }
+
+    #[test]
+    fn test_is_currency_alias() {
+        assert!(is_currency_alias("usd"));
+        assert!(is_currency_alias("euro"));
+        assert!(is_currency_alias("$"));
+        assert!(!is_currency_alias("km"));
+    }
+
+    #[test]
+    fn test_parse_ecb_xml() {
+        let xml = r#"<?xml version="1.0" encoding="UTF-8"?>
+<gesmes:Envelope xmlns:gesmes="http://www.gesmes.org/xml/2002-08-01" xmlns="http://www.ecb.int/vocabulary/2002-08-01/eurofxref">
+    <gesmes:subject>Reference rates</gesmes:subject>
+    <Cube>
+        <Cube time='2026-03-26'>
+            <Cube currency='USD' rate='1.0832'/>
+            <Cube currency='JPY' rate='161.94'/>
+            <Cube currency='GBP' rate='0.83450'/>
+        </Cube>
+    </Cube>
+</gesmes:Envelope>"#;
+
+        let rates = parse_ecb_xml(xml).unwrap();
+        assert!((rates.rates["USD"] - 1.0832).abs() < 0.001);
+        assert!((rates.rates["GBP"] - 0.8345).abs() < 0.001);
+        assert!((rates.rates["JPY"] - 161.94).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_cache_roundtrip() {
+        let rates = CurrencyRates {
+            date: "2026-03-26".to_string(),
+            rates: {
+                let mut m = HashMap::new();
+                m.insert("USD".to_string(), 1.0832);
+                m.insert("GBP".to_string(), 0.8345);
+                m
+            },
+        };
+        let json = serde_json::to_string(&rates).unwrap();
+        let parsed: CurrencyRates = serde_json::from_str(&json).unwrap();
+        assert_eq!(parsed.rates["USD"], 1.0832);
+    }
+}

crates/owlry-core/src/providers/converter/mod.rs

@@ -0,0 +1,183 @@
+mod currency;
+mod parser;
+mod units;
+
+use super::{DynamicProvider, LaunchItem, ProviderType};
+
+const PROVIDER_TYPE_ID: &str = "conv";
+const PROVIDER_ICON: &str = "edit-find-replace-symbolic";
+
+pub struct ConverterProvider;
+
+impl ConverterProvider {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl DynamicProvider for ConverterProvider {
+    fn name(&self) -> &str {
+        "Converter"
+    }
+
+    fn provider_type(&self) -> ProviderType {
+        ProviderType::Plugin(PROVIDER_TYPE_ID.into())
+    }
+
+    fn priority(&self) -> u32 {
+        9_000
+    }
+
+    fn query(&self, query: &str) -> Vec<LaunchItem> {
+        let query_str = query.trim();
+        // Strip prefix
+        let input = if let Some(rest) = query_str.strip_prefix('>') {
+            rest.trim()
+        } else {
+            query_str
+        };
+
+        let parsed = match parser::parse_conversion(input) {
+            Some(p) => p,
+            None => return Vec::new(),
+        };
+
+        let results = if let Some(ref target) = parsed.target_unit {
+            units::convert_to(&parsed.value, &parsed.from_unit, target)
+                .into_iter()
+                .collect()
+        } else {
+            units::convert_common(&parsed.value, &parsed.from_unit)
+        };
+
+        results
+            .into_iter()
+            .map(|r| LaunchItem {
+                id: format!("conv:{}:{}:{}", parsed.from_unit, r.target_symbol, r.value),
+                name: r.display_value.clone(),
+                description: Some(format!(
+                    "{} {} = {}",
+                    format_number(parsed.value),
+                    parsed.from_symbol,
+                    r.display_value,
+                )),
+                icon: Some(PROVIDER_ICON.into()),
+                provider: ProviderType::Plugin(PROVIDER_TYPE_ID.into()),
+                command: format!(
+                    "printf '%s' '{}' | wl-copy",
+                    r.raw_value.replace('\'', "'\\''")
+                ),
+                terminal: false,
+                tags: vec!["converter".into(), "units".into()],
+            })
+            .collect()
+    }
+}
+
+fn format_number(n: f64) -> String {
+    if n.fract() == 0.0 && n.abs() < 1e15 {
+        let i = n as i64;
+        if i.abs() >= 1000 {
+            format_with_separators(i)
+        } else {
+            format!("{}", i)
+        }
+    } else {
+        format!("{:.4}", n)
+            .trim_end_matches('0')
+            .trim_end_matches('.')
+            .to_string()
+    }
+}
+
+pub(crate) fn format_with_separators(n: i64) -> String {
+    let s = n.abs().to_string();
+    let mut result = String::new();
+    for (i, c) in s.chars().rev().enumerate() {
+        if i > 0 && i % 3 == 0 {
+            result.push(',');
+        }
+        result.push(c);
+    }
+    if n < 0 {
+        result.push('-');
+    }
+    result.chars().rev().collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn query(input: &str) -> Vec<LaunchItem> {
+        ConverterProvider::new().query(input)
+    }
+
+    #[test]
+    fn test_prefix_trigger() {
+        let r = query("> 100 km to mi");
+        assert!(!r.is_empty());
+    }
+
+    #[test]
+    fn test_auto_detect() {
+        let r = query("100 km to mi");
+        assert!(!r.is_empty());
+    }
+
+    #[test]
+    fn test_common_conversions() {
+        let r = query("> 100 km");
+        assert!(r.len() > 1);
+    }
+
+    #[test]
+    fn test_temperature() {
+        let r = query("102F to C");
+        assert!(!r.is_empty());
+    }
+
+    #[test]
+    fn test_nonsense_returns_empty() {
+        assert!(query("hello world").is_empty());
+    }
+
+    #[test]
+    fn test_provider_type() {
+        assert_eq!(
+            ConverterProvider::new().provider_type(),
+            ProviderType::Plugin("conv".into())
+        );
+    }
+
+    #[test]
+    fn test_no_double_unit() {
+        let r = query("100 km to mi");
+        if let Some(item) = r.first() {
+            let desc = item.description.as_deref().unwrap();
+            assert!(!desc.ends_with(" mi mi"), "double unit in: {}", desc);
+        }
+    }
+
+    #[test]
+    fn test_format_number_integer() {
+        assert_eq!(format_number(42.0), "42");
+    }
+
+    #[test]
+    fn test_format_number_large_integer() {
+        assert_eq!(format_number(1000000.0), "1,000,000");
+    }
+
+    #[test]
+    fn test_format_number_decimal() {
+        assert_eq!(format_number(3.14), "3.14");
+    }
+
+    #[test]
+    fn test_format_with_separators() {
+        assert_eq!(format_with_separators(1234567), "1,234,567");
+        assert_eq!(format_with_separators(999), "999");
+        assert_eq!(format_with_separators(-1234), "-1,234");
+    }
+}

crates/owlry-core/src/providers/converter/parser.rs

@@ -0,0 +1,235 @@
+use super::units;
+
+pub struct ParsedQuery {
+    pub value: f64,
+    pub from_unit: String,
+    pub from_symbol: String,
+    pub target_unit: Option<String>,
+}
+
+pub fn parse_conversion(input: &str) -> Option<ParsedQuery> {
+    let input = input.trim();
+    if input.is_empty() {
+        return None;
+    }
+
+    // Extract leading number
+    let (value, rest) = extract_number(input)?;
+    let rest = rest.trim();
+
+    if rest.is_empty() {
+        return None;
+    }
+
+    // Split on " to " or " in " (case-insensitive)
+    let (from_str, target_str) = split_on_connector(rest);
+
+    // Resolve from unit
+    let from_lower = from_str.trim().to_lowercase();
+    let from_symbol = units::find_unit(&from_lower)?;
+
+    let from_symbol_str = from_symbol.to_string();
+
+    // Resolve target unit if present
+    let target_unit = target_str.and_then(|t| {
+        let t_lower = t.trim().to_lowercase();
+        if t_lower.is_empty() {
+            None
+        } else {
+            units::find_unit(&t_lower).map(|_| t_lower)
+        }
+    });
+
+    Some(ParsedQuery {
+        value,
+        from_unit: from_lower,
+        from_symbol: from_symbol_str,
+        target_unit,
+    })
+}
+
+fn extract_number(input: &str) -> Option<(f64, &str)> {
+    let bytes = input.as_bytes();
+    let mut i = 0;
+
+    // Optional negative sign
+    if i < bytes.len() && bytes[i] == b'-' {
+        i += 1;
+    }
+
+    // Must have at least one digit or start with .
+    if i >= bytes.len() {
+        return None;
+    }
+
+    let start_digits = i;
+
+    // Integer part
+    while i < bytes.len() && bytes[i].is_ascii_digit() {
+        i += 1;
+    }
+
+    // Decimal part
+    if i < bytes.len() && bytes[i] == b'.' {
+        i += 1;
+        while i < bytes.len() && bytes[i].is_ascii_digit() {
+            i += 1;
+        }
+    }
+
+    if i == start_digits && !(i > 0 && bytes[0] == b'-') {
+        // No digits found (and not just a negative sign before a dot)
+        // Handle ".5" case
+        if bytes[start_digits] == b'.' {
+            // already advanced past dot above
+        } else {
+            return None;
+        }
+    }
+
+    if i == 0 || (i == 1 && bytes[0] == b'-') {
+        return None;
+    }
+
+    let num_str = &input[..i];
+    let value: f64 = num_str.parse().ok()?;
+    let rest = &input[i..];
+
+    Some((value, rest))
+}
+
+fn split_on_connector(input: &str) -> (&str, Option<&str>) {
+    let lower = input.to_lowercase();
+
+    // Try " to " first
+    if let Some(pos) = lower.find(" to ") {
+        let from = &input[..pos];
+        let target = &input[pos + 4..];
+        return (from, Some(target));
+    }
+
+    // Try " in "
+    if let Some(pos) = lower.find(" in ") {
+        let from = &input[..pos];
+        let target = &input[pos + 4..];
+        return (from, Some(target));
+    }
+
+    (input, None)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_number_and_unit_with_space() {
+        let p = parse_conversion("100 km").unwrap();
+        assert!((p.value - 100.0).abs() < 0.001);
+        assert_eq!(p.from_unit, "km");
+        assert!(p.target_unit.is_none());
+    }
+
+    #[test]
+    fn test_number_and_unit_no_space() {
+        let p = parse_conversion("100km").unwrap();
+        assert!((p.value - 100.0).abs() < 0.001);
+        assert_eq!(p.from_unit, "km");
+    }
+
+    #[test]
+    fn test_with_target_to() {
+        let p = parse_conversion("100 km to mi").unwrap();
+        assert!((p.value - 100.0).abs() < 0.001);
+        assert_eq!(p.from_unit, "km");
+        assert_eq!(p.target_unit.as_deref(), Some("mi"));
+    }
+
+    #[test]
+    fn test_with_target_in() {
+        let p = parse_conversion("100 km in mi").unwrap();
+        assert_eq!(p.target_unit.as_deref(), Some("mi"));
+    }
+
+    #[test]
+    fn test_temperature_no_space() {
+        let p = parse_conversion("102F to C").unwrap();
+        assert!((p.value - 102.0).abs() < 0.001);
+        assert_eq!(p.from_unit, "f");
+        assert_eq!(p.target_unit.as_deref(), Some("c"));
+    }
+
+    #[test]
+    fn test_temperature_with_space() {
+        let p = parse_conversion("102 F in K").unwrap();
+        assert!((p.value - 102.0).abs() < 0.001);
+        assert_eq!(p.from_unit, "f");
+        assert_eq!(p.target_unit.as_deref(), Some("k"));
+    }
+
+    #[test]
+    fn test_decimal_number() {
+        let p = parse_conversion("3.5 kg to lb").unwrap();
+        assert!((p.value - 3.5).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_decimal_starting_with_dot() {
+        let p = parse_conversion(".5 kg").unwrap();
+        assert!((p.value - 0.5).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_full_unit_names() {
+        let p = parse_conversion("100 kilometers to miles").unwrap();
+        assert_eq!(p.from_unit, "kilometers");
+        assert_eq!(p.target_unit.as_deref(), Some("miles"));
+    }
+
+    #[test]
+    fn test_case_insensitive() {
+        let p = parse_conversion("100 KM TO MI").unwrap();
+        assert_eq!(p.from_unit, "km");
+        assert_eq!(p.target_unit.as_deref(), Some("mi"));
+    }
+
+    #[test]
+    fn test_currency() {
+        let p = parse_conversion("100 eur to usd").unwrap();
+        assert_eq!(p.from_unit, "eur");
+        assert_eq!(p.target_unit.as_deref(), Some("usd"));
+    }
+
+    #[test]
+    fn test_no_number_returns_none() {
+        assert!(parse_conversion("km to mi").is_none());
+    }
+
+    #[test]
+    fn test_unknown_unit_returns_none() {
+        assert!(parse_conversion("100 xyz to abc").is_none());
+    }
+
+    #[test]
+    fn test_empty_returns_none() {
+        assert!(parse_conversion("").is_none());
+    }
+
+    #[test]
+    fn test_number_only_returns_none() {
+        assert!(parse_conversion("100").is_none());
+    }
+
+    #[test]
+    fn test_compound_unit_alias() {
+        let p = parse_conversion("100 km/h to mph").unwrap();
+        assert_eq!(p.from_unit, "km/h");
+        assert_eq!(p.target_unit.as_deref(), Some("mph"));
+    }
+
+    #[test]
+    fn test_multi_word_unit() {
+        let p = parse_conversion("100 fl_oz to ml").unwrap();
+        assert_eq!(p.from_unit, "fl_oz");
+    }
+}

crates/owlry-core/src/providers/converter/units.rs

@@ -0,0 +1,944 @@
+use std::collections::HashMap;
+use std::sync::LazyLock;
+
+use super::currency;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Category {
+    Temperature,
+    Length,
+    Weight,
+    Volume,
+    Speed,
+    Area,
+    Data,
+    Time,
+    Pressure,
+    Energy,
+    Currency,
+}
+
+#[derive(Clone)]
+enum Conversion {
+    Factor(f64),
+    Custom {
+        to_base: fn(f64) -> f64,
+        from_base: fn(f64) -> f64,
+    },
+}
+
+#[derive(Clone)]
+pub(crate) struct UnitDef {
+    _id: &'static str,
+    symbol: &'static str,
+    aliases: &'static [&'static str],
+    category: Category,
+    conversion: Conversion,
+}
+
+impl UnitDef {
+    fn to_base(&self, value: f64) -> f64 {
+        match &self.conversion {
+            Conversion::Factor(f) => value * f,
+            Conversion::Custom { to_base, .. } => to_base(value),
+        }
+    }
+
+    fn convert_from_base(&self, value: f64) -> f64 {
+        match &self.conversion {
+            Conversion::Factor(f) => value / f,
+            Conversion::Custom { from_base, .. } => from_base(value),
+        }
+    }
+}
+
+pub struct ConversionResult {
+    pub value: f64,
+    pub raw_value: String,
+    pub display_value: String,
+    pub target_symbol: String,
+}
+
+static UNITS: LazyLock<Vec<UnitDef>> = LazyLock::new(build_unit_table);
+static ALIAS_MAP: LazyLock<HashMap<String, usize>> = LazyLock::new(|| {
+    let mut map = HashMap::new();
+    for (i, unit) in UNITS.iter().enumerate() {
+        for alias in unit.aliases {
+            map.insert(alias.to_lowercase(), i);
+        }
+    }
+    map
+});
+
+// Common conversions per category (symbols to show when no target specified)
+static COMMON_TARGETS: LazyLock<HashMap<Category, Vec<&'static str>>> = LazyLock::new(|| {
+    let mut m = HashMap::new();
+    m.insert(Category::Temperature, vec!["°C", "°F", "K"]);
+    m.insert(Category::Length, vec!["m", "km", "ft", "mi", "in"]);
+    m.insert(Category::Weight, vec!["kg", "lb", "oz", "g", "st"]);
+    m.insert(Category::Volume, vec!["l", "gal", "ml", "cup", "fl oz"]);
+    m.insert(Category::Speed, vec!["km/h", "mph", "m/s", "kn"]);
+    m.insert(Category::Area, vec!["m²", "ft²", "ac", "ha", "km²"]);
+    m.insert(Category::Data, vec!["MB", "GB", "MiB", "GiB", "TB"]);
+    m.insert(Category::Time, vec!["s", "min", "h", "d", "wk"]);
+    m.insert(Category::Pressure, vec!["bar", "psi", "atm", "hPa", "mmHg"]);
+    m.insert(Category::Energy, vec!["kJ", "kcal", "kWh", "BTU", "Wh"]);
+    m.insert(Category::Currency, vec!["USD", "EUR", "GBP", "JPY", "CNY"]);
+    m
+});
+
+pub fn find_unit(alias: &str) -> Option<&'static str> {
+    let lower = alias.to_lowercase();
+    if let Some(&i) = ALIAS_MAP.get(&lower) {
+        return Some(UNITS[i].symbol);
+    }
+    currency::resolve_currency_code(&lower)
+}
+
+pub fn lookup_unit(alias: &str) -> Option<(usize, &UnitDef)> {
+    let lower = alias.to_lowercase();
+    ALIAS_MAP.get(&lower).map(|&i| (i, &UNITS[i]))
+}
+
+pub fn convert_to(value: &f64, from: &str, to: &str) -> Option<ConversionResult> {
+    // Try currency first — currency aliases (dollar, euro, etc.) aren't in the UNITS table
+    if currency::is_currency_alias(from) || currency::is_currency_alias(to) {
+        return convert_currency(*value, from, to);
+    }
+
+    let (_, from_def) = lookup_unit(from)?;
+    let (_, to_def) = lookup_unit(to)?;
+
+    // Currency via UNITS table (shouldn't reach here, but just in case)
+    if from_def.category == Category::Currency || to_def.category == Category::Currency {
+        return convert_currency(*value, from, to);
+    }
+
+    // Must be same category
+    if from_def.category != to_def.category {
+        return None;
+    }
+
+    let base_value = from_def.to_base(*value);
+    let result = to_def.convert_from_base(base_value);
+
+    Some(format_result(result, to_def.symbol))
+}
+
+pub fn convert_common(value: &f64, from: &str) -> Vec<ConversionResult> {
+    // Try currency first — currency aliases (dollar, euro, etc.) aren't in the UNITS table
+    if currency::is_currency_alias(from) {
+        return convert_currency_common(*value, from);
+    }
+
+    let (_, from_def) = match lookup_unit(from) {
+        Some(u) => u,
+        None => return vec![],
+    };
+
+    let category = from_def.category;
+    let from_symbol = from_def.symbol;
+
+    if category == Category::Currency {
+        return convert_currency_common(*value, from);
+    }
+
+    let targets = match COMMON_TARGETS.get(&category) {
+        Some(t) => t,
+        None => return vec![],
+    };
+
+    let base_value = from_def.to_base(*value);
+
+    targets
+        .iter()
+        .filter(|&&sym| sym != from_symbol)
+        .filter_map(|&sym| {
+            let (_, to_def) = lookup_unit(sym)?;
+            let result = to_def.convert_from_base(base_value);
+            Some(format_result(result, to_def.symbol))
+        })
+        .take(5)
+        .collect()
+}
+
+fn convert_currency(value: f64, from: &str, to: &str) -> Option<ConversionResult> {
+    let rates = currency::get_rates()?;
+    let from_code = currency::resolve_currency_code(from)?;
+    let to_code = currency::resolve_currency_code(to)?;
+
+    let from_rate = if from_code == "EUR" { 1.0 } else { *rates.rates.get(from_code)? };
+    let to_rate = if to_code == "EUR" { 1.0 } else { *rates.rates.get(to_code)? };
+
+    let result = value / from_rate * to_rate;
+    Some(format_currency_result(result, to_code))
+}
+
+fn convert_currency_common(value: f64, from: &str) -> Vec<ConversionResult> {
+    let rates = match currency::get_rates() {
+        Some(r) => r,
+        None => return vec![],
+    };
+    let from_code = match currency::resolve_currency_code(from) {
+        Some(c) => c,
+        None => return vec![],
+    };
+
+    let targets = COMMON_TARGETS.get(&Category::Currency).unwrap();
+    let from_rate = if from_code == "EUR" {
+        1.0
+    } else {
+        match rates.rates.get(from_code) {
+            Some(&r) => r,
+            None => return vec![],
+        }
+    };
+
+    targets
+        .iter()
+        .filter(|&&sym| sym != from_code)
+        .filter_map(|&sym| {
+            let to_rate = if sym == "EUR" { 1.0 } else { *rates.rates.get(sym)? };
+            let result = value / from_rate * to_rate;
+            Some(format_currency_result(result, sym))
+        })
+        .take(5)
+        .collect()
+}
+
+fn format_result(value: f64, symbol: &str) -> ConversionResult {
+    let raw = if value.fract() == 0.0 && value.abs() < 1e15 {
+        format!("{}", value as i64)
+    } else {
+        format!("{:.4}", value)
+            .trim_end_matches('0')
+            .trim_end_matches('.')
+            .to_string()
+    };
+
+    let display = if value.abs() >= 1000.0 && value.fract() == 0.0 && value.abs() < 1e15 {
+        super::format_with_separators(value as i64)
+    } else {
+        raw.clone()
+    };
+
+    ConversionResult {
+        value,
+        raw_value: raw,
+        display_value: format!("{} {}", display, symbol),
+        target_symbol: symbol.to_string(),
+    }
+}
+
+fn format_currency_result(value: f64, code: &str) -> ConversionResult {
+    let raw = format!("{:.2}", value);
+    let display = raw.clone();
+
+    ConversionResult {
+        value,
+        raw_value: raw,
+        display_value: format!("{} {}", display, code),
+        target_symbol: code.to_string(),
+    }
+}
+
+fn build_unit_table() -> Vec<UnitDef> {
+    vec![
+        // Temperature (base: Kelvin)
+        UnitDef {
+            _id: "celsius",
+            symbol: "°C",
+            aliases: &["c", "°c", "celsius", "degc", "centigrade"],
+            category: Category::Temperature,
+            conversion: Conversion::Custom {
+                to_base: |v| v + 273.15,
+                from_base: |v| v - 273.15,
+            },
+        },
+        UnitDef {
+            _id: "fahrenheit",
+            symbol: "°F",
+            aliases: &["f", "°f", "fahrenheit", "degf"],
+            category: Category::Temperature,
+            conversion: Conversion::Custom {
+                to_base: |v| (v - 32.0) * 5.0 / 9.0 + 273.15,
+                from_base: |v| (v - 273.15) * 9.0 / 5.0 + 32.0,
+            },
+        },
+        UnitDef {
+            _id: "kelvin",
+            symbol: "K",
+            aliases: &["k", "kelvin"],
+            category: Category::Temperature,
+            conversion: Conversion::Factor(1.0), // base
+        },
+        // Length (base: meter)
+        UnitDef {
+            _id: "millimeter",
+            symbol: "mm",
+            aliases: &["mm", "millimeter", "millimeters", "millimetre"],
+            category: Category::Length,
+            conversion: Conversion::Factor(0.001),
+        },
+        UnitDef {
+            _id: "centimeter",
+            symbol: "cm",
+            aliases: &["cm", "centimeter", "centimeters", "centimetre"],
+            category: Category::Length,
+            conversion: Conversion::Factor(0.01),
+        },
+        UnitDef {
+            _id: "meter",
+            symbol: "m",
+            aliases: &["m", "meter", "meters", "metre", "metres"],
+            category: Category::Length,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "kilometer",
+            symbol: "km",
+            aliases: &["km", "kms", "kilometer", "kilometers", "kilometre"],
+            category: Category::Length,
+            conversion: Conversion::Factor(1000.0),
+        },
+        UnitDef {
+            _id: "inch",
+            symbol: "in",
+            aliases: &["in", "inch", "inches"],
+            category: Category::Length,
+            conversion: Conversion::Factor(0.0254),
+        },
+        UnitDef {
+            _id: "foot",
+            symbol: "ft",
+            aliases: &["ft", "foot", "feet"],
+            category: Category::Length,
+            conversion: Conversion::Factor(0.3048),
+        },
+        UnitDef {
+            _id: "yard",
+            symbol: "yd",
+            aliases: &["yd", "yard", "yards"],
+            category: Category::Length,
+            conversion: Conversion::Factor(0.9144),
+        },
+        UnitDef {
+            _id: "mile",
+            symbol: "mi",
+            aliases: &["mi", "mile", "miles"],
+            category: Category::Length,
+            conversion: Conversion::Factor(1609.344),
+        },
+        UnitDef {
+            _id: "nautical_mile",
+            symbol: "nmi",
+            aliases: &["nmi", "nautical_mile", "nautical_miles"],
+            category: Category::Length,
+            conversion: Conversion::Factor(1852.0),
+        },
+        // Weight (base: kg)
+        UnitDef {
+            _id: "milligram",
+            symbol: "mg",
+            aliases: &["mg", "milligram", "milligrams"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(0.000001),
+        },
+        UnitDef {
+            _id: "gram",
+            symbol: "g",
+            aliases: &["g", "gram", "grams"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(0.001),
+        },
+        UnitDef {
+            _id: "kilogram",
+            symbol: "kg",
+            aliases: &["kg", "kilogram", "kilograms", "kilo", "kilos"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "tonne",
+            symbol: "t",
+            aliases: &["t", "ton", "tons", "tonne", "tonnes", "metric_ton"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(1000.0),
+        },
+        UnitDef {
+            _id: "short_ton",
+            symbol: "short_ton",
+            aliases: &["short_ton", "ton_us"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(907.185),
+        },
+        UnitDef {
+            _id: "ounce",
+            symbol: "oz",
+            aliases: &["oz", "ounce", "ounces"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(0.0283495),
+        },
+        UnitDef {
+            _id: "pound",
+            symbol: "lb",
+            aliases: &["lb", "lbs", "pound", "pounds"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(0.453592),
+        },
+        UnitDef {
+            _id: "stone",
+            symbol: "st",
+            aliases: &["st", "stone", "stones"],
+            category: Category::Weight,
+            conversion: Conversion::Factor(6.35029),
+        },
+        // Volume (base: liter)
+        UnitDef {
+            _id: "milliliter",
+            symbol: "ml",
+            aliases: &["ml", "milliliter", "milliliters", "millilitre"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.001),
+        },
+        UnitDef {
+            _id: "liter",
+            symbol: "l",
+            aliases: &["l", "liter", "liters", "litre", "litres"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "us_gallon",
+            symbol: "gal",
+            aliases: &["gal", "gallon", "gallons"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(3.78541),
+        },
+        UnitDef {
+            _id: "imp_gallon",
+            symbol: "imp gal",
+            aliases: &["imp_gal", "gal_uk", "imperial_gallon"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(4.54609),
+        },
+        UnitDef {
+            _id: "quart",
+            symbol: "qt",
+            aliases: &["qt", "quart", "quarts"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.946353),
+        },
+        UnitDef {
+            _id: "pint",
+            symbol: "pt",
+            aliases: &["pt", "pint", "pints"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.473176),
+        },
+        UnitDef {
+            _id: "cup",
+            symbol: "cup",
+            aliases: &["cup", "cups"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.236588),
+        },
+        UnitDef {
+            _id: "fluid_ounce",
+            symbol: "fl oz",
+            aliases: &["floz", "fl_oz", "fluid_ounce", "fluid_ounces"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.0295735),
+        },
+        UnitDef {
+            _id: "tablespoon",
+            symbol: "tbsp",
+            aliases: &["tbsp", "tablespoon", "tablespoons"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.0147868),
+        },
+        UnitDef {
+            _id: "teaspoon",
+            symbol: "tsp",
+            aliases: &["tsp", "teaspoon", "teaspoons"],
+            category: Category::Volume,
+            conversion: Conversion::Factor(0.00492892),
+        },
+        // Speed (base: m/s)
+        UnitDef {
+            _id: "mps",
+            symbol: "m/s",
+            aliases: &["m/s", "mps", "meters_per_second"],
+            category: Category::Speed,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "kmh",
+            symbol: "km/h",
+            aliases: &["km/h", "kmh", "kph", "kilometers_per_hour"],
+            category: Category::Speed,
+            conversion: Conversion::Factor(0.277778),
+        },
+        UnitDef {
+            _id: "mph",
+            symbol: "mph",
+            aliases: &["mph", "miles_per_hour"],
+            category: Category::Speed,
+            conversion: Conversion::Factor(0.44704),
+        },
+        UnitDef {
+            _id: "knot",
+            symbol: "kn",
+            aliases: &["kn", "kt", "knot", "knots"],
+            category: Category::Speed,
+            conversion: Conversion::Factor(0.514444),
+        },
+        UnitDef {
+            _id: "fps",
+            symbol: "ft/s",
+            aliases: &["ft/s", "fps", "feet_per_second"],
+            category: Category::Speed,
+            conversion: Conversion::Factor(0.3048),
+        },
+        // Area (base: m²)
+        UnitDef {
+            _id: "sqmm",
+            symbol: "mm²",
+            aliases: &["mm2", "sqmm", "square_millimeter"],
+            category: Category::Area,
+            conversion: Conversion::Factor(0.000001),
+        },
+        UnitDef {
+            _id: "sqcm",
+            symbol: "cm²",
+            aliases: &["cm2", "sqcm", "square_centimeter"],
+            category: Category::Area,
+            conversion: Conversion::Factor(0.0001),
+        },
+        UnitDef {
+            _id: "sqm",
+            symbol: "m²",
+            aliases: &["m2", "sqm", "square_meter", "square_meters"],
+            category: Category::Area,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "sqkm",
+            symbol: "km²",
+            aliases: &["km2", "sqkm", "square_kilometer"],
+            category: Category::Area,
+            conversion: Conversion::Factor(1000000.0),
+        },
+        UnitDef {
+            _id: "sqft",
+            symbol: "ft²",
+            aliases: &["ft2", "sqft", "square_foot", "square_feet"],
+            category: Category::Area,
+            conversion: Conversion::Factor(0.092903),
+        },
+        UnitDef {
+            _id: "acre",
+            symbol: "ac",
+            aliases: &["ac", "acre", "acres"],
+            category: Category::Area,
+            conversion: Conversion::Factor(4046.86),
+        },
+        UnitDef {
+            _id: "hectare",
+            symbol: "ha",
+            aliases: &["ha", "hectare", "hectares"],
+            category: Category::Area,
+            conversion: Conversion::Factor(10000.0),
+        },
+        // Data (base: byte)
+        UnitDef {
+            _id: "byte",
+            symbol: "B",
+            aliases: &["b", "byte", "bytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "kilobyte",
+            symbol: "KB",
+            aliases: &["kb", "kilobyte", "kilobytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1000.0),
+        },
+        UnitDef {
+            _id: "megabyte",
+            symbol: "MB",
+            aliases: &["mb", "megabyte", "megabytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_000_000.0),
+        },
+        UnitDef {
+            _id: "gigabyte",
+            symbol: "GB",
+            aliases: &["gb", "gigabyte", "gigabytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_000_000_000.0),
+        },
+        UnitDef {
+            _id: "terabyte",
+            symbol: "TB",
+            aliases: &["tb", "terabyte", "terabytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_000_000_000_000.0),
+        },
+        UnitDef {
+            _id: "kibibyte",
+            symbol: "KiB",
+            aliases: &["kib", "kibibyte", "kibibytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1024.0),
+        },
+        UnitDef {
+            _id: "mebibyte",
+            symbol: "MiB",
+            aliases: &["mib", "mebibyte", "mebibytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_048_576.0),
+        },
+        UnitDef {
+            _id: "gibibyte",
+            symbol: "GiB",
+            aliases: &["gib", "gibibyte", "gibibytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_073_741_824.0),
+        },
+        UnitDef {
+            _id: "tebibyte",
+            symbol: "TiB",
+            aliases: &["tib", "tebibyte", "tebibytes"],
+            category: Category::Data,
+            conversion: Conversion::Factor(1_099_511_627_776.0),
+        },
+        // Time (base: second)
+        UnitDef {
+            _id: "second",
+            symbol: "s",
+            aliases: &["s", "sec", "second", "seconds"],
+            category: Category::Time,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "minute",
+            symbol: "min",
+            aliases: &["min", "minute", "minutes"],
+            category: Category::Time,
+            conversion: Conversion::Factor(60.0),
+        },
+        UnitDef {
+            _id: "hour",
+            symbol: "h",
+            aliases: &["h", "hr", "hour", "hours"],
+            category: Category::Time,
+            conversion: Conversion::Factor(3600.0),
+        },
+        UnitDef {
+            _id: "day",
+            symbol: "d",
+            aliases: &["d", "day", "days"],
+            category: Category::Time,
+            conversion: Conversion::Factor(86400.0),
+        },
+        UnitDef {
+            _id: "week",
+            symbol: "wk",
+            aliases: &["wk", "week", "weeks"],
+            category: Category::Time,
+            conversion: Conversion::Factor(604800.0),
+        },
+        UnitDef {
+            _id: "month",
+            symbol: "mo",
+            aliases: &["mo", "month", "months"],
+            category: Category::Time,
+            conversion: Conversion::Factor(2_592_000.0),
+        },
+        UnitDef {
+            _id: "year",
+            symbol: "yr",
+            aliases: &["yr", "year", "years"],
+            category: Category::Time,
+            conversion: Conversion::Factor(31_536_000.0),
+        },
+        // Pressure (base: Pa)
+        UnitDef {
+            _id: "pascal",
+            symbol: "Pa",
+            aliases: &["pa", "pascal", "pascals"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "hectopascal",
+            symbol: "hPa",
+            aliases: &["hpa", "hectopascal"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(100.0),
+        },
+        UnitDef {
+            _id: "kilopascal",
+            symbol: "kPa",
+            aliases: &["kpa", "kilopascal"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(1000.0),
+        },
+        UnitDef {
+            _id: "bar",
+            symbol: "bar",
+            aliases: &["bar", "bars"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(100_000.0),
+        },
+        UnitDef {
+            _id: "millibar",
+            symbol: "mbar",
+            aliases: &["mbar", "millibar"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(100.0),
+        },
+        UnitDef {
+            _id: "psi",
+            symbol: "psi",
+            aliases: &["psi", "pounds_per_square_inch"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(6894.76),
+        },
+        UnitDef {
+            _id: "atmosphere",
+            symbol: "atm",
+            aliases: &["atm", "atmosphere", "atmospheres"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(101_325.0),
+        },
+        UnitDef {
+            _id: "mmhg",
+            symbol: "mmHg",
+            aliases: &["mmhg", "torr"],
+            category: Category::Pressure,
+            conversion: Conversion::Factor(133.322),
+        },
+        // Energy (base: Joule)
+        UnitDef {
+            _id: "joule",
+            symbol: "J",
+            aliases: &["j", "joule", "joules"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(1.0),
+        },
+        UnitDef {
+            _id: "kilojoule",
+            symbol: "kJ",
+            aliases: &["kj", "kilojoule", "kilojoules"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(1000.0),
+        },
+        UnitDef {
+            _id: "calorie",
+            symbol: "cal",
+            aliases: &["cal", "calorie", "calories"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(4.184),
+        },
+        UnitDef {
+            _id: "kilocalorie",
+            symbol: "kcal",
+            aliases: &["kcal", "kilocalorie", "kilocalories"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(4184.0),
+        },
+        UnitDef {
+            _id: "watt_hour",
+            symbol: "Wh",
+            aliases: &["wh", "watt_hour"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(3600.0),
+        },
+        UnitDef {
+            _id: "kilowatt_hour",
+            symbol: "kWh",
+            aliases: &["kwh", "kilowatt_hour"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(3_600_000.0),
+        },
+        UnitDef {
+            _id: "btu",
+            symbol: "BTU",
+            aliases: &["btu", "british_thermal_unit"],
+            category: Category::Energy,
+            conversion: Conversion::Factor(1055.06),
+        },
+    ]
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_celsius_to_fahrenheit() {
+        let r = convert_to(&100.0, "c", "f").unwrap();
+        assert!((r.value - 212.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_fahrenheit_to_celsius() {
+        let r = convert_to(&32.0, "f", "c").unwrap();
+        assert!((r.value - 0.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_body_temp_f_to_c() {
+        let r = convert_to(&98.6, "f", "c").unwrap();
+        assert!((r.value - 37.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_km_to_miles() {
+        let r = convert_to(&100.0, "km", "mi").unwrap();
+        assert!((r.value - 62.1371).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_miles_to_km() {
+        let r = convert_to(&1.0, "mi", "km").unwrap();
+        assert!((r.value - 1.60934).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_kg_to_lb() {
+        let r = convert_to(&1.0, "kg", "lb").unwrap();
+        assert!((r.value - 2.20462).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_lb_to_kg() {
+        let r = convert_to(&100.0, "lbs", "kg").unwrap();
+        assert!((r.value - 45.3592).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_liters_to_gallons() {
+        let r = convert_to(&3.78541, "l", "gal").unwrap();
+        assert!((r.value - 1.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_kmh_to_mph() {
+        let r = convert_to(&100.0, "kmh", "mph").unwrap();
+        assert!((r.value - 62.1371).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_gb_to_mb() {
+        let r = convert_to(&1.0, "gb", "mb").unwrap();
+        assert!((r.value - 1000.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_gib_to_mib() {
+        let r = convert_to(&1.0, "gib", "mib").unwrap();
+        assert!((r.value - 1024.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_hours_to_minutes() {
+        let r = convert_to(&2.5, "h", "min").unwrap();
+        assert!((r.value - 150.0).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_bar_to_psi() {
+        let r = convert_to(&1.0, "bar", "psi").unwrap();
+        assert!((r.value - 14.5038).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_kcal_to_kj() {
+        let r = convert_to(&1.0, "kcal", "kj").unwrap();
+        assert!((r.value - 4.184).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_sqm_to_sqft() {
+        let r = convert_to(&1.0, "m2", "ft2").unwrap();
+        assert!((r.value - 10.7639).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_unknown_unit_returns_none() {
+        assert!(convert_to(&100.0, "xyz", "abc").is_none());
+    }
+
+    #[test]
+    fn test_cross_category_returns_none() {
+        assert!(convert_to(&100.0, "km", "kg").is_none());
+    }
+
+    #[test]
+    fn test_convert_common_returns_results() {
+        let results = convert_common(&100.0, "km");
+        assert!(!results.is_empty());
+        assert!(results.len() <= 5);
+    }
+
+    #[test]
+    fn test_convert_common_excludes_source() {
+        let results = convert_common(&100.0, "km");
+        for r in &results {
+            assert_ne!(r.target_symbol, "km");
+        }
+    }
+
+    #[test]
+    fn test_alias_case_insensitive() {
+        let r1 = convert_to(&100.0, "KM", "MI").unwrap();
+        let r2 = convert_to(&100.0, "km", "mi").unwrap();
+        assert!((r1.value - r2.value).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_full_name_alias() {
+        let r = convert_to(&100.0, "kilometers", "miles").unwrap();
+        assert!((r.value - 62.1371).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_format_currency_two_decimals() {
+        let r = convert_to(&1.0, "km", "mi").unwrap();
+        // display_value should have reasonable formatting
+        assert!(!r.display_value.is_empty());
+    }
+
+    #[test]
+    fn test_currency_alias_convert_to() {
+        // "dollar" and "euro" are aliases, not in the UNITS table
+        let r = convert_to(&20.0, "dollar", "euro");
+        // May return None if ECB rates unavailable (network), but should not panic
+        // In a network-available environment, this should return Some
+        if let Some(r) = r {
+            assert!(r.value > 0.0);
+            assert_eq!(r.target_symbol, "EUR");
+        }
+    }
+
+    #[test]
+    fn test_currency_alias_convert_common() {
+        let results = convert_common(&20.0, "dollar");
+        // May be empty if ECB rates unavailable, but should not panic
+        for r in &results {
+            assert!(r.value > 0.0);
+        }
+    }
+
+    #[test]
+    fn test_display_value_no_double_unit() {
+        let r = convert_to(&100.0, "km", "mi").unwrap();
+        // display_value should contain the symbol exactly once
+        let count = r.display_value.matches(&r.target_symbol).count();
+        assert_eq!(count, 1, "display_value '{}' should contain '{}' exactly once", r.display_value, r.target_symbol);
+    }
+}

crates/owlry-core/src/providers/mod.rs

@@ -2,6 +2,7 @@
 mod application;
 mod command;
 pub(crate) mod calculator;
+pub(crate) mod converter;
 pub(crate) mod system;
 
 // Native plugin bridge