/**
 * Built-in tools that come with the application
 */

import type { ToolDefinition, BuiltinToolHandler, ToolRegistryEntry } from './types.js';

// ============================================================================
// Get Current Time Tool
// ============================================================================

interface GetTimeArgs {
	timezone?: string;
	format?: 'iso' | 'locale' | 'unix';
}

const getTimeDefinition: ToolDefinition = {
	type: 'function',
	function: {
		name: 'get_current_time',
		description: 'Get the current date and time. Can optionally specify timezone and format.',
		parameters: {
			type: 'object',
			properties: {
				timezone: {
					type: 'string',
					description: 'IANA timezone name (e.g., "America/New_York", "Europe/London"). Defaults to local timezone.'
				},
				format: {
					type: 'string',
					description: 'Output format: "iso" for ISO 8601, "locale" for localized string, "unix" for Unix timestamp.',
					enum: ['iso', 'locale', 'unix']
				}
			}
		}
	}
};

const getTimeHandler: BuiltinToolHandler<GetTimeArgs> = (args) => {
	const now = new Date();
	const format = args.format ?? 'iso';

	try {
		if (args.timezone) {
			const options: Intl.DateTimeFormatOptions = {
				timeZone: args.timezone,
				year: 'numeric',
				month: '2-digit',
				day: '2-digit',
				hour: '2-digit',
				minute: '2-digit',
				second: '2-digit',
				hour12: false
			};

			if (format === 'locale') {
				return new Intl.DateTimeFormat('en-US', {
					...options,
					dateStyle: 'full',
					timeStyle: 'long'
				}).format(now);
			}

			const formatter = new Intl.DateTimeFormat('en-CA', options);
			const parts = formatter.formatToParts(now);
			const get = (type: string) => parts.find(p => p.type === type)?.value ?? '';
			return `${get('year')}-${get('month')}-${get('day')}T${get('hour')}:${get('minute')}:${get('second')}`;
		}

		switch (format) {
			case 'unix':
				return Math.floor(now.getTime() / 1000);
			case 'locale':
				return now.toLocaleString();
			case 'iso':
			default:
				return now.toISOString();
		}
	} catch {
		return { error: `Invalid timezone: ${args.timezone}` };
	}
};

// ============================================================================
// Calculate Tool (Safe Math Expression Parser)
// ============================================================================

interface CalculateArgs {
	expression: string;
	precision?: number;
}

const calculateDefinition: ToolDefinition = {
	type: 'function',
	function: {
		name: 'calculate',
		description: 'Compute a mathematical expression. Supports basic arithmetic (+, -, *, /, ^), parentheses, and common functions (sqrt, sin, cos, tan, log, exp, abs, round, floor, ceil).',
		parameters: {
			type: 'object',
			properties: {
				expression: {
					type: 'string',
					description: 'The mathematical expression to compute (e.g., "2 + 2", "sqrt(16)", "sin(3.14159/2)")'
				},
				precision: {
					type: 'number',
					description: 'Number of decimal places for the result (default: 10)'
				}
			},
			required: ['expression']
		}
	}
};

/**
 * Safe math expression parser using recursive descent
 * Parses and computes expressions without using dynamic code execution
 */
class MathParser {
	private pos = 0;
	private expr = '';

	private readonly functions: Record<string, (x: number) => number> = {
		sqrt: Math.sqrt,
		sin: Math.sin,
		cos: Math.cos,
		tan: Math.tan,
		log: Math.log,
		log10: Math.log10,
		exp: Math.exp,
		abs: Math.abs,
		round: Math.round,
		floor: Math.floor,
		ceil: Math.ceil
	};

	private readonly constants: Record<string, number> = {
		PI: Math.PI,
		pi: Math.PI,
		E: Math.E,
		e: Math.E
	};

	parse(expression: string): number {
		this.expr = expression.replace(/\s+/g, '');
		this.pos = 0;
		const result = this.parseExpression();
		if (this.pos < this.expr.length) {
			throw new Error(`Unexpected character at position ${this.pos}: ${this.expr[this.pos]}`);
		}
		return result;
	}

	private parseExpression(): number {
		return this.parseAddSub();
	}

	private parseAddSub(): number {
		let left = this.parseMulDiv();
		while (this.pos < this.expr.length) {
			const op = this.expr[this.pos];
			if (op === '+') {
				this.pos++;
				left = left + this.parseMulDiv();
			} else if (op === '-') {
				this.pos++;
				left = left - this.parseMulDiv();
			} else {
				break;
			}
		}
		return left;
	}

	private parseMulDiv(): number {
		let left = this.parsePower();
		while (this.pos < this.expr.length) {
			const op = this.expr[this.pos];
			if (op === '*') {
				this.pos++;
				left = left * this.parsePower();
			} else if (op === '/') {
				this.pos++;
				const right = this.parsePower();
				if (right === 0) throw new Error('Division by zero');
				left = left / right;
			} else if (op === '%') {
				this.pos++;
				left = left % this.parsePower();
			} else {
				break;
			}
		}
		return left;
	}

	private parsePower(): number {
		const left = this.parseUnary();
		if (this.pos < this.expr.length && (this.expr[this.pos] === '^' || this.expr.slice(this.pos, this.pos + 2) === '**')) {
			if (this.expr[this.pos] === '^') {
				this.pos++;
			} else {
				this.pos += 2;
			}
			return Math.pow(left, this.parsePower());
		}
		return left;
	}

	private parseUnary(): number {
		if (this.expr[this.pos] === '-') {
			this.pos++;
			return -this.parseUnary();
		}
		if (this.expr[this.pos] === '+') {
			this.pos++;
			return this.parseUnary();
		}
		return this.parsePrimary();
	}

	private parsePrimary(): number {
		if (this.expr[this.pos] === '(') {
			this.pos++;
			const result = this.parseExpression();
			if (this.expr[this.pos] !== ')') {
				throw new Error('Missing closing parenthesis');
			}
			this.pos++;
			return result;
		}

		const funcMatch = this.expr.slice(this.pos).match(/^([a-zA-Z_][a-zA-Z0-9_]*)/);
		if (funcMatch) {
			const name = funcMatch[1];
			this.pos += name.length;

			if (this.constants[name] !== undefined) {
				return this.constants[name];
			}

			const fn = this.functions[name.toLowerCase()];
			if (!fn) {
				throw new Error(`Unknown function or constant: ${name}`);
			}

			if (this.expr[this.pos] !== '(') {
				throw new Error(`Expected '(' after function ${name}`);
			}
			this.pos++;
			const arg = this.parseExpression();
			if (this.expr[this.pos] !== ')') {
				throw new Error('Missing closing parenthesis for function');
			}
			this.pos++;
			return fn(arg);
		}

		const numMatch = this.expr.slice(this.pos).match(/^(\d+\.?\d*|\.\d+)/);
		if (numMatch) {
			this.pos += numMatch[1].length;
			return parseFloat(numMatch[1]);
		}

		throw new Error(`Unexpected character at position ${this.pos}: ${this.expr[this.pos] || 'end of expression'}`);
	}
}

const mathParser = new MathParser();

const calculateHandler: BuiltinToolHandler<CalculateArgs> = (args) => {
	const { expression, precision = 10 } = args;

	try {
		const result = mathParser.parse(expression);

		if (typeof result !== 'number' || !isFinite(result)) {
			return { error: 'Expression resulted in invalid number (infinity or NaN)' };
		}

		return Number(result.toFixed(precision));
	} catch (error) {
		return { error: `Failed to compute expression: ${error instanceof Error ? error.message : 'Unknown error'}` };
	}
};

// ============================================================================
// Fetch URL Tool (Web Content Retrieval)
// ============================================================================

interface FetchUrlArgs {
	url: string;
	extract?: 'text' | 'title' | 'links' | 'all';
	maxLength?: number;
}

const fetchUrlDefinition: ToolDefinition = {
	type: 'function',
	function: {
		name: 'fetch_url',
		description: 'Fetch content from a URL and extract text, title, or links. Useful for retrieving web page content.',
		parameters: {
			type: 'object',
			properties: {
				url: {
					type: 'string',
					description: 'The URL to fetch (must be a valid HTTP/HTTPS URL)'
				},
				extract: {
					type: 'string',
					description: 'What to extract: "text" for main content, "title" for page title, "links" for all links, "all" for everything',
					enum: ['text', 'title', 'links', 'all']
				},
				maxLength: {
					type: 'number',
					description: 'Maximum length of extracted text (default: 5000 characters)'
				}
			},
			required: ['url']
		}
	}
};

/**
 * Try to fetch URL via backend proxy first (bypasses CORS), fall back to direct fetch
 */
async function fetchViaProxy(url: string, maxLength: number): Promise<{ html: string; finalUrl: string } | { error: string }> {
	// Try backend proxy first
	try {
		const proxyResponse = await fetch('/api/v1/proxy/fetch', {
			method: 'POST',
			headers: { 'Content-Type': 'application/json' },
			body: JSON.stringify({ url, maxLength })
		});

		if (proxyResponse.ok) {
			const data = await proxyResponse.json();
			return { html: data.content, finalUrl: data.url };
		}

		// If proxy returns an error, extract it
		const errorData = await proxyResponse.json().catch(() => null);
		if (errorData?.error) {
			return { error: errorData.error };
		}
	} catch {
		// Proxy not available, try direct fetch
	}

	// Fall back to direct fetch (may fail due to CORS)
	try {
		const controller = new AbortController();
		const timeout = setTimeout(() => controller.abort(), 10000);

		const response = await fetch(url, {
			signal: controller.signal,
			headers: {
				'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
			}
		});

		clearTimeout(timeout);

		if (!response.ok) {
			return { error: `HTTP ${response.status}: ${response.statusText}` };
		}

		const html = await response.text();
		return { html, finalUrl: response.url };
	} catch (error) {
		if (error instanceof Error && error.name === 'AbortError') {
			return { error: 'Request timed out after 10 seconds' };
		}
		// Provide helpful error message for CORS issues
		const message = error instanceof Error ? error.message : 'Unknown error';
		if (message.includes('NetworkError') || message.includes('CORS')) {
			return { error: `Cannot fetch external URL due to browser security restrictions. The backend proxy is not available. Start the backend server to enable URL fetching.` };
		}
		return { error: `Failed to fetch URL: ${message}` };
	}
}

const fetchUrlHandler: BuiltinToolHandler<FetchUrlArgs> = async (args) => {
	const { url, extract = 'text', maxLength = 5000 } = args;

	try {
		const parsedUrl = new URL(url);
		if (!['http:', 'https:'].includes(parsedUrl.protocol)) {
			return { error: 'Only HTTP and HTTPS URLs are supported' };
		}

		// Fetch via proxy or direct
		const result = await fetchViaProxy(url, maxLength);
		if ('error' in result) {
			return result;
		}

		const { html, finalUrl } = result;

		const titleMatch = html.match(/<title[^>]*>([^<]+)<\/title>/i);
		const title = titleMatch ? titleMatch[1].trim() : null;

		if (extract === 'title') {
			return title ?? 'No title found';
		}

		const stripHtml = (str: string) => {
			return str
				.replace(/<script[^>]*>[\s\S]*?<\/script>/gi, '')
				.replace(/<style[^>]*>[\s\S]*?<\/style>/gi, '')
				.replace(/<[^>]+>/g, ' ')
				.replace(/\s+/g, ' ')
				.trim();
		};

		const linkMatches = [...html.matchAll(/<a[^>]+href=["']([^"']+)["'][^>]*>([^<]*)<\/a>/gi)];
		const links = linkMatches.slice(0, 50).map(match => ({
			url: match[1],
			text: match[2].trim()
		})).filter(link => link.url && !link.url.startsWith('#'));

		if (extract === 'links') {
			return links;
		}

		const text = stripHtml(html).substring(0, maxLength);

		if (extract === 'text') {
			return text;
		}

		return {
			title,
			text,
			links: links.slice(0, 20),
			url: finalUrl
		};
	} catch (error) {
		return { error: `Failed to fetch URL: ${error instanceof Error ? error.message : 'Unknown error'}` };
	}
};

// ============================================================================
// Get Location Tool
// ============================================================================

interface GetLocationArgs {
	highAccuracy?: boolean;
}

interface LocationResult {
	latitude: number;
	longitude: number;
	accuracy: number;
	city?: string;
	country?: string;
}

const getLocationDefinition: ToolDefinition = {
	type: 'function',
	function: {
		name: 'get_location',
		description: 'Get the user\'s current location (city, country, coordinates). Call this IMMEDIATELY when you need location for weather, local info, or nearby places. Do NOT ask the user where they are - use this tool instead.',
		parameters: {
			type: 'object',
			properties: {
				highAccuracy: {
					type: 'boolean',
					description: 'Whether to request high accuracy GPS location (may take longer and use more battery). Default is false.'
				}
			}
		}
	}
};

const getLocationHandler: BuiltinToolHandler<GetLocationArgs> = async (args) => {
	const { highAccuracy = false } = args;

	// Check if geolocation is available
	if (!navigator.geolocation) {
		return { error: 'Geolocation is not supported by this browser' };
	}

	try {
		const position = await new Promise<GeolocationPosition>((resolve, reject) => {
			navigator.geolocation.getCurrentPosition(resolve, reject, {
				enableHighAccuracy: highAccuracy,
				timeout: 30000, // 30 seconds - user needs time to accept permission prompt
				maximumAge: 300000 // Cache for 5 minutes
			});
		});

		const result: LocationResult = {
			latitude: position.coords.latitude,
			longitude: position.coords.longitude,
			accuracy: Math.round(position.coords.accuracy)
		};

		// Try to get city/country via reverse geocoding (using a free service)
		try {
			const geoResponse = await fetch(
				`https://nominatim.openstreetmap.org/reverse?lat=${result.latitude}&lon=${result.longitude}&format=json`,
				{
					headers: {
						'User-Agent': 'OllamaWebUI/1.0'
					}
				}
			);

			if (geoResponse.ok) {
				const geoData = await geoResponse.json();
				if (geoData.address) {
					result.city = geoData.address.city || geoData.address.town || geoData.address.village || geoData.address.municipality;
					result.country = geoData.address.country;
				}
			}
		} catch {
			// Reverse geocoding failed, but we still have coordinates
		}

		return {
			location: result,
			message: result.city
				? `User is located in ${result.city}${result.country ? ', ' + result.country : ''}`
				: `User is at coordinates ${result.latitude.toFixed(4)}, ${result.longitude.toFixed(4)}`
		};
	} catch (error) {
		if (error instanceof GeolocationPositionError) {
			switch (error.code) {
				case error.PERMISSION_DENIED:
					return {
						error: 'Location permission denied',
						suggestion: 'Ask the user for their city/location directly, then use web_search with that location.'
					};
				case error.POSITION_UNAVAILABLE:
					return {
						error: 'Location services unavailable on this device',
						suggestion: 'Ask the user for their city/location directly, then use web_search with that location.'
					};
				case error.TIMEOUT:
					return {
						error: 'Location request timed out',
						suggestion: 'Ask the user for their city/location directly, then use web_search with that location.'
					};
			}
		}
		return {
			error: `Failed to get location: ${error instanceof Error ? error.message : 'Unknown error'}`,
			suggestion: 'Ask the user for their city/location directly, then use web_search with that location.'
		};
	}
};

// ============================================================================
// Web Search Tool
// ============================================================================

interface WebSearchArgs {
	query: string;
	maxResults?: number;
}

interface WebSearchResult {
	title: string;
	url: string;
	snippet: string;
}

const webSearchDefinition: ToolDefinition = {
	type: 'function',
	function: {
		name: 'web_search',
		description: 'Search the web for current information. You MUST call this tool immediately when the user asks about weather, news, current events, sports, stocks, prices, or any real-time information. Do NOT ask the user for clarification - just search. If no location is specified for weather, call get_location first.',
		parameters: {
			type: 'object',
			properties: {
				query: {
					type: 'string',
					description: 'The search query (e.g., "weather Berlin tomorrow", "latest news", "Bitcoin price")'
				},
				maxResults: {
					type: 'number',
					description: 'Maximum number of results to return (1-10, default 5)'
				}
			},
			required: ['query']
		}
	}
};

const webSearchHandler: BuiltinToolHandler<WebSearchArgs> = async (args) => {
	const { query, maxResults = 5 } = args;

	if (!query || query.trim() === '') {
		return { error: 'Search query is required' };
	}

	// Try backend proxy first
	try {
		const proxyResponse = await fetch('/api/v1/proxy/search', {
			method: 'POST',
			headers: { 'Content-Type': 'application/json' },
			body: JSON.stringify({ query, maxResults: Math.min(Math.max(1, maxResults), 10) })
		});

		if (proxyResponse.ok) {
			const data = await proxyResponse.json();
			const results = data.results as WebSearchResult[];

			if (results.length === 0) {
				return { message: 'No search results found for the query.', query };
			}

			// Format results for the AI
			return {
				query,
				resultCount: results.length,
				results: results.map((r, i) => ({
					rank: i + 1,
					title: r.title,
					url: r.url,
					snippet: r.snippet || '(no snippet available)'
				}))
			};
		}

		// If proxy returns an error, extract it
		const errorData = await proxyResponse.json().catch(() => null);
		if (errorData?.error) {
			return { error: errorData.error };
		}
	} catch {
		// Proxy not available
	}

	return {
		error: 'Web search is not available. Please start the backend server to enable web search functionality.',
		hint: 'Run the backend server with: cd backend && go run cmd/server/main.go'
	};
};

// ============================================================================
// Registry of Built-in Tools
// ============================================================================

export const builtinTools: Map<string, ToolRegistryEntry> = new Map([
	['get_current_time', {
		definition: getTimeDefinition,
		handler: getTimeHandler as unknown as BuiltinToolHandler,
		isBuiltin: true
	}],
	['calculate', {
		definition: calculateDefinition,
		handler: calculateHandler as unknown as BuiltinToolHandler,
		isBuiltin: true
	}],
	['fetch_url', {
		definition: fetchUrlDefinition,
		handler: fetchUrlHandler as unknown as BuiltinToolHandler,
		isBuiltin: true
	}],
	['get_location', {
		definition: getLocationDefinition,
		handler: getLocationHandler as unknown as BuiltinToolHandler,
		isBuiltin: true
	}],
	['web_search', {
		definition: webSearchDefinition,
		handler: webSearchHandler as unknown as BuiltinToolHandler,
		isBuiltin: true
	}]
]);

/** Get all built-in tool definitions for Ollama API */
export function getBuiltinToolDefinitions(): ToolDefinition[] {
	return Array.from(builtinTools.values()).map(entry => entry.definition);
}

// Log available builtin tools at startup
console.log('[Builtin Tools] Available:', Array.from(builtinTools.keys()));