import { randomBytes } from "crypto";
import type { EnvVariable, GenerateOptions } from "./types";

// Secret Generation
// ============================================================================

/**
 * Generate a secure random secret
 */
export function generateSecret(length: number = 32): string {
  return randomBytes(Math.ceil(length / 2))
    .toString('hex')
    .slice(0, length);
}

// ============================================================================
// File Generation
// ============================================================================

/**
 * Generate .env file content
 */
export function generateEnvFile(
  variables: EnvVariable[],
  environment: string,
  options: GenerateOptions
): string {
  const lines: string[] = [];

  // Header
  if (environment === 'example') {
    lines.push('# Environment Configuration Template');
    lines.push('# Copy this file to .env.local and fill in the values');
  } else {
    lines.push(`# ${environment.charAt(0).toUpperCase() + environment.slice(1)} Environment Configuration`);
  }
  lines.push(`# Generated: ${new Date().toISOString()}`);
  lines.push('');

  // Group by category
  const categories = new Map<string, EnvVariable[]>();
  variables.forEach(v => {
    const cat = v.category;
    if (!categories.has(cat)) categories.set(cat, []);
    categories.get(cat)!.push(v);
  });

  // Generate sections
  for (const [category, vars] of categories) {
    lines.push('# ' + '='.repeat(77));
    lines.push(`# ${category.toUpperCase()}`);
    lines.push('# ' + '='.repeat(77));
    lines.push('');

    for (const envVar of vars) {
      // Add description
      if (options.format !== 'minimal') {
        lines.push(`# ${envVar.description}`);

        if (options.includeExamples && envVar.example) {
          lines.push(`# Example: ${envVar.example}`);
        }

        if (options.securityWarnings && envVar.sensitive) {
          lines.push('# ⚠️  SECURITY WARNING: This is a sensitive credential');
          lines.push('#    - Never commit this to version control');
          lines.push('#    - Use a strong, randomly generated value');
          lines.push('#    - Store securely (e.g., password manager, secrets vault)');
        }
      }

      // Generate value
      let value = '';
      if (environment === 'example') {
        value = envVar.example || 'your-value-here';
      } else if (options.generateSecrets && envVar.sensitive && !envVar.example?.includes('sk-')) {
        value = generateSecret(options.secretLength);
      } else {
        value = envVar.defaultValue || envVar.example || '';
      }

      // Add variable
      if (environment === 'example' || !value) {
        lines.push(`${envVar.name}="${value}"`);
      } else {
        lines.push(`${envVar.name}="${value}"`);
      }

      lines.push('');
    }

    lines.push('');
  }

  return lines.join('\n');
}

/**
 * Generate TypeScript type definitions
 */
export function generateTypeDefs(variables: EnvVariable[]): string {
  const lines: string[] = [];

  lines.push('/**');
  lines.push(' * Environment Variables Type Definitions');
  lines.push(' * Generated by generate-env skill');
  lines.push(' */');
  lines.push('');
  lines.push('declare global {');
  lines.push('  namespace NodeJS {');
  lines.push('    interface ProcessEnv {');

  // Group by category
  const categories = new Map<string, EnvVariable[]>();
  variables.forEach(v => {
    const cat = v.category;
    if (!categories.has(cat)) categories.set(cat, []);
    categories.get(cat)!.push(v);
  });

  for (const [category, vars] of categories) {
    lines.push(`      // ${category.charAt(0).toUpperCase() + category.slice(1)}`);

    for (const envVar of vars) {
      let type = 'string';
      if (envVar.name === 'NODE_ENV') {
        type = "'development' | 'production' | 'test'";
      } else if (envVar.name === 'PORT') {
        type = 'string';
      }

      const optional = envVar.required ? '' : '?';
      lines.push(`      ${envVar.name}${optional}: ${type};`);
    }

    lines.push('');
  }

  lines.push('    }');
  lines.push('  }');
  lines.push('}');
  lines.push('');
  lines.push('export {};');

  return lines.join('\n');
}

/**
 * Generate Zod validation schema
 */
export function generateValidation(variables: EnvVariable[]): string {
  const lines: string[] = [];

  lines.push("import { z } from 'zod';");
  lines.push('');
  lines.push('/**');
  lines.push(' * Environment Variables Validation Schema');
  lines.push(' * Generated by generate-env skill');
  lines.push(' */');
  lines.push('');
  lines.push('export const envSchema = z.object({');

  // Group by category
  const categories = new Map<string, EnvVariable[]>();
  variables.forEach(v => {
    const cat = v.category;
    if (!categories.has(cat)) categories.set(cat, []);
    categories.get(cat)!.push(v);
  });

  for (const [category, vars] of categories) {
    lines.push(`  // ${category.charAt(0).toUpperCase() + category.slice(1)}`);

    for (const envVar of vars) {
      let validation = envVar.validation || 'z.string()';

      // Add specific validations
      if (envVar.name.endsWith('_URL')) {
        validation = 'z.string().url()';
      } else if (envVar.name.endsWith('_EMAIL')) {
        validation = 'z.string().email()';
      } else if (envVar.sensitive && !envVar.validation) {
        validation = 'z.string().min(1)';
      }

      if (!envVar.required) {
        validation += '.optional()';
      }

      lines.push(`  ${envVar.name}: ${validation},`);
    }

    lines.push('');
  }

  lines.push('});');
  lines.push('');
  lines.push('export type Env = z.infer<typeof envSchema>;');
  lines.push('');
  lines.push('/**');
  lines.push(' * Validate environment variables at runtime');
  lines.push(' */');
  lines.push('export function validateEnv(): Env {');
  lines.push('  const parsed = envSchema.safeParse(process.env);');
  lines.push('');
  lines.push('  if (!parsed.success) {');
  lines.push("    console.error('❌ Invalid environment variables:', parsed.error.flatten().fieldErrors);");
  lines.push("    throw new Error('Invalid environment variables');");
  lines.push('  }');
  lines.push('');
  lines.push('  return parsed.data;');
  lines.push('}');

  return lines.join('\n');
}

/**
 * Generate metadata file
 */
export function generateMetadata(variables: EnvVariable[], options: GenerateOptions): string {
  return JSON.stringify({
    generatedAt: new Date().toISOString(),
    totalVariables: variables.length,
    categories: Array.from(new Set(variables.map(v => v.category))).sort(),
    sensitiveCount: variables.filter(v => v.sensitive).length,
    requiredCount: variables.filter(v => v.required).length,
    options: {
      templateOnly: options.templateOnly,
      generateSecrets: options.generateSecrets,
      withTypes: options.withTypes,
      withValidation: options.withValidation,
    },
    variables: variables.map(v => ({
      name: v.name,
      category: v.category,
      required: v.required,
      sensitive: v.sensitive,
    })),
  }, null, 2);
}