import type { APIRoute } from 'astro';

/**
 * Spintax Pattern Validator
 * Check syntax before running 10k generations
 */

function validateGodToken(request: Request): boolean {
    const token = request.headers.get('X-God-Token') ||
        request.headers.get('Authorization')?.replace('Bearer ', '') ||
        new URL(request.url).searchParams.get('token');

    const godToken = process.env.GOD_MODE_TOKEN || import.meta.env.GOD_MODE_TOKEN;
    if (!godToken) return true;
    return token === godToken;
}

interface ValidationError {
    type: string;
    position: number;
    message: string;
}

/**
 * Validate spintax pattern syntax
 */
function validateSpintax(pattern: string): { valid: boolean; errors: ValidationError[] } {
    const errors: ValidationError[] = [];
    let braceStack: number[] = [];
    let inBraces = false;
    let currentDepth = 0;
    const maxDepth = 3;

    for (let i = 0; i < pattern.length; i++) {
        const char = pattern[i];
        const prevChar = i > 0 ? pattern[i - 1] : '';

        // Check for opening brace
        if (char === '{' && prevChar !== '\\') {
            braceStack.push(i);
            currentDepth++;
            inBraces = true;

            if (currentDepth > maxDepth) {
                errors.push({
                    type: 'max_depth',
                    position: i,
                    message: `Nested too deep (max ${maxDepth} levels)`
                });
            }
        }

        // Check for closing brace
        if (char === '}' && prevChar !== '\\') {
            if (braceStack.length === 0) {
                errors.push({
                    type: 'unmatched_closing',
                    position: i,
                    message: 'Closing brace without opening brace'
                });
            } else {
                const openPos = braceStack.pop();
                const content = pattern.substring(openPos! + 1, i);

                // Check for empty braces
                if (content.trim() === '') {
                    errors.push({
                        type: 'empty_braces',
                        position: openPos!,
                        message: 'Empty option set {}'
                    });
                }

                // Check for missing pipes
                if (!content.includes('|')) {
                    errors.push({
                        type: 'no_alternatives',
                        position: openPos!,
                        message: 'Option set must contain at least one pipe |'
                    });
                }

                // Check for empty options
                const options = content.split('|');
                for (let j = 0; j < options.length; j++) {
                    if (options[j].trim() === '') {
                        errors.push({
                            type: 'empty_option',
                            position: openPos! + content.indexOf('||'),
                            message: 'Empty option between pipes'
                        });
                    }
                }

                currentDepth--;
            }
            inBraces = braceStack.length > 0;
        }
    }

    // Check for unclosed braces
    if (braceStack.length > 0) {
        for (const pos of braceStack) {
            errors.push({
                type: 'unclosed_brace',
                position: pos,
                message: 'Opening brace not closed'
            });
        }
    }

    return {
        valid: errors.length === 0,
        errors
    };
}

/**
 * Generate a few sample variations
 */
function generateSamples(pattern: string, count: number = 3): string[] {
    const samples: string[] = [];

    for (let i = 0; i < count; i++) {
        let result = pattern;
        const regex = /\{([^{}]+)\}/g;

        result = result.replace(regex, (match, content) => {
            const options = content.split('|').map((s: string) => s.trim());
            return options[Math.floor(Math.random() * options.length)];
        });

        samples.push(result);
    }

    return samples;
}

export const POST: APIRoute = async ({ request }) => {
    if (!validateGodToken(request)) {
        return new Response(JSON.stringify({ error: 'Unauthorized' }), {
            status: 401,
            headers: { 'Content-Type': 'application/json' }
        });
    }

    try {
        const { pattern, max_depth = 3 } = await request.json();

        if (!pattern) {
            return new Response(JSON.stringify({
                error: 'Missing pattern'
            }), {
                status: 400,
                headers: { 'Content-Type': 'application/json' }
            });
        }

        const validation = validateSpintax(pattern);
        const samples = validation.valid ? generateSamples(pattern, 5) : [];

        return new Response(JSON.stringify({
            pattern,
            valid: validation.valid,
            errors: validation.errors,
            samples: validation.valid ? samples : null,
            stats: {
                length: pattern.length,
                braces: (pattern.match(/\{/g) || []).length,
                pipes: (pattern.match(/\|/g) || []).length
            },
            recommendation: validation.valid
                ? '✅ Pattern is valid - safe to use in batch generation'
                : '❌ Fix errors before using in production',
            timestamp: new Date().toISOString()
        }), {
            status: 200,
            headers: { 'Content-Type': 'application/json' }
        });

    } catch (error: any) {
        return new Response(JSON.stringify({
            error: 'Validation failed',
            details: error.message
        }), {
            status: 500,
            headers: { 'Content-Type': 'application/json' }
        });
    }
};

export const GET: APIRoute = async ({ request }) => {
    if (!validateGodToken(request)) {
        return new Response(JSON.stringify({ error: 'Unauthorized' }), {
            status: 401,
            headers: { 'Content-Type': 'application/json' }
        });
    }

    return new Response(JSON.stringify({
        endpoint: 'POST /api/intelligence/spintax/validate',
        description: 'Validate spintax patterns before batch generation',
        examples: {
            valid: '{Hello|Hi|Hey} {world|there|friend}!',
            invalid: '{Hello|Hi} {world',
            nested: '{The {best|top} {solution|answer}}',
            empty: '{|option}  // Error: empty option'
        },
        errors_detected: [
            'unmatched_braces',
            'empty_option_sets',
            'no_alternatives',
            'max_depth_exceeded'
        ]
    }, null, 2), {
        status: 200,
        headers: { 'Content-Type': 'application/json' }
    });
};