import { existsSync, readFileSync, writeFileSync } from "node:fs";
import path from "node:path";
import process from "node:process";
import chalk from "chalk";

/**
 * Keys that are allowed to exist in .env but not in .env.example
 * These are environment-specific variables that should not be synced
 */
const IGNORED_KEYS = new Set(["SERVER_IS_DEMO_ENV", "SERVER_DEMO_POST_WHITELIST", "EXTENSION_API_URL"]);

/**
 * Parse env file content into structured data
 * @param {string} content - The content of the env file
 * @returns {Array<{type: 'comment'|'empty'|'variable', content: string, key?: string, value?: string}>}
 */
function parseEnvFile(content) {
    const lines = content.split("\n");
    const parsed = [];

    for (const line of lines) {
        const trimmed = line.trim();

        // Empty line
        if (trimmed === "") {
            parsed.push({ type: "empty", content: line });
            continue;
        }

        // Comment line
        if (trimmed.startsWith("#")) {
            parsed.push({ type: "comment", content: line });
            continue;
        }

        // Variable line
        const match = line.match(/^([^=]+)=(.*)$/);
        if (match) {
            const key = match[1].trim();
            const value = match[2];
            parsed.push({
                type: "variable",
                content: line,
                key,
                value,
            });
        } else {
            // Malformed line, treat as comment
            parsed.push({ type: "comment", content: line });
        }
    }

    return parsed;
}

/**
 * Build a map of existing variables from .env file
 * @param {Array} parsedEnv - Parsed env data
 * @returns {Map<string, string>}
 */
function buildExistingVariablesMap(parsedEnv) {
    const map = new Map();
    for (const item of parsedEnv) {
        if (item.type === "variable") {
            map.set(item.key, item.value);
        }
    }
    return map;
}

/**
 * Read version from root package.json
 * @param {string} cwd - current working directory
 * @returns {string|null}
 */
function readRootVersion(cwd) {
    try {
        const pkgPath = path.resolve(cwd, "package.json");
        const pkgContent = readFileSync(pkgPath, "utf-8");
        const pkgJson = JSON.parse(pkgContent);
        return pkgJson.version || null;
    } catch {
        return null;
    }
}

/**
 * Sync .env file with .env.example
 * @param {string} examplePath - Path to .env.example
 * @param {string} envPath - Path to .env
 * @param {string|null} rootVersion - root package.json version
 */
function syncEnvFile(examplePath, envPath, rootVersion) {
    // Check if .env.example exists
    if (!existsSync(examplePath)) {
        console.log(chalk.red("❌ .env.example file not found"));
        process.exit(1);
    }

    // Read .env.example
    const exampleContent = readFileSync(examplePath, "utf-8");
    const parsedExample = parseEnvFile(exampleContent);

    // Build a set of valid keys from .env.example
    const exampleKeys = new Set();
    for (const item of parsedExample) {
        if (item.type === "variable") {
            exampleKeys.add(item.key);
        }
    }

    // Read .env if exists, otherwise create empty
    let parsedEnv = [];
    let existingVariables = new Map();

    if (existsSync(envPath)) {
        const envContent = readFileSync(envPath, "utf-8");
        parsedEnv = parseEnvFile(envContent);
        existingVariables = buildExistingVariablesMap(parsedEnv);
    }

    // Track changes
    const addedKeys = [];
    const removedKeys = [];
    const keptKeys = [];
    const migratedKeys = []; // Version-specific migrations

    // Version-specific tweak: for 25.1.0, bump JWT_EXPIRES_IN from 1d to 30d
    if (rootVersion === "25.1.0") {
        const jwtExpiresIn = existingVariables.get("JWT_EXPIRES_IN");
        if (jwtExpiresIn === "1d") {
            existingVariables.set("JWT_EXPIRES_IN", "30d");
            migratedKeys.push({ key: "JWT_EXPIRES_IN", from: "1d", to: "30d", reason: "version 25.1.0" });
        }
    }

    // Find removed keys (exist in .env but not in .env.example)
    for (const [key] of existingVariables) {
        if (!exampleKeys.has(key) && !IGNORED_KEYS.has(key)) {
            removedKeys.push(key);
        }
    }

    // Build result: preserve .env structure (comments, empty lines, order)
    // Only modify variables: update values, remove obsolete, append new
    const result = [];
    const processedKeys = new Set();

    // First pass: keep .env structure, update variable values, skip removed keys
    for (const item of parsedEnv) {
        if (item.type === "variable") {
            if (removedKeys.includes(item.key)) {
                // Skip removed variables
                continue;
            }
            // Use migrated value if available, otherwise keep existing
            const value = existingVariables.get(item.key);
            result.push(`${item.key}=${value}`);
            processedKeys.add(item.key);
            keptKeys.push(item.key);
        } else {
            // Keep all comments and empty lines from .env
            result.push(item.content);
        }
    }

    // Second pass: append new variables from .env.example (not in .env)
    for (const item of parsedExample) {
        if (item.type === "variable" && !processedKeys.has(item.key)) {
            result.push(item.content);
            addedKeys.push(item.key);
        }
    }

    // Check if there are any changes
    const hasChanges = addedKeys.length > 0 || removedKeys.length > 0 || migratedKeys.length > 0;

    if (!hasChanges) {
        console.log(chalk.blue("ℹ No changes detected. .env is already in sync with .env.example"));
        return;
    }

    // Display migration summary first
    if (migratedKeys.length > 0) {
        console.log("");
        console.log(chalk.cyan(`⚙ Migrated ${migratedKeys.length} variable(s) for version compatibility:`));
        migratedKeys.forEach(({ key, from, to, reason }) => {
            console.log(chalk.cyan(`  ~ ${key}: ${from} → ${to} (${reason})`));
        });
    }

    // Display changes summary
    console.log("");
    if (addedKeys.length > 0) {
        console.log(chalk.green(`✓ Added ${addedKeys.length} new variable(s):`));
        addedKeys.forEach((key) => {
            console.log(chalk.green(`  + ${key}`));
        });
    }

    if (removedKeys.length > 0) {
        console.log("");
        console.log(chalk.yellow(`⚠ Removed ${removedKeys.length} obsolete variable(s):`));
        removedKeys.forEach((key) => {
            console.log(chalk.yellow(`  - ${key}`));
        });
    }

    if (keptKeys.length > 0) {
        console.log("");
        console.log(chalk.blue(`ℹ Kept ${keptKeys.length} existing variable(s) with their original values`));
    }

    // Write back to .env
    const newContent = result.join("\n");
    writeFileSync(envPath, newContent, "utf-8");

    console.log("");
    console.log(chalk.green("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"));
    console.log(chalk.green("✓ .env file synced successfully"));
    console.log(chalk.green("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"));
}

/**
 * Main function
 */
function main() {
    console.log(chalk.blue("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"));
    console.log(chalk.blue("📋 Syncing .env file with .env.example"));
    console.log(chalk.blue("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"));

    const cwd = process.cwd();
    const examplePath = path.resolve(cwd, ".env.example");
    const envPath = path.resolve(cwd, ".env");
    const rootVersion = readRootVersion(cwd);

    syncEnvFile(examplePath, envPath, rootVersion);
}

main();