'use strict';

const fs = require('fs');
const path = require('path');

const PACKAGE_MANAGER_SHIM_DIR_NAME = '.notemd-package-manager-bin';

function packageManagerCandidates() {
    return [
        { command: 'pnpm', versionArgs: ['--version'], prefix: [] },
        { command: 'corepack', versionArgs: ['pnpm', '--version'], prefix: ['pnpm'] },
        { command: 'bun', versionArgs: ['x', 'pnpm', '--version'], prefix: ['x', 'pnpm'] }
    ];
}

function buildPackageManagerRuntime(candidate, cwd) {
    if (candidate.command === 'pnpm') {
        return {
            command: candidate.command,
            prefix: candidate.prefix,
            env: normalizePathEnv(process.env),
            shimDir: null
        };
    }

    const shimDir = ensurePnpmShimDir(candidate, cwd);
    return {
        command: candidate.command,
        prefix: candidate.prefix,
        env: prependToPath(process.env, shimDir),
        shimDir
    };
}

function ensurePnpmShimDir(candidate, cwd) {
    const shimDir = path.join(cwd, PACKAGE_MANAGER_SHIM_DIR_NAME);
    const shimPath = path.join(shimDir, 'pnpm');
    const cmdShimPath = path.join(shimDir, 'pnpm.cmd');
    const shimBody = buildPnpmShimBody(candidate);
    const cmdShimBody = buildPnpmCmdShimBody(candidate);

    fs.mkdirSync(shimDir, { recursive: true });
    if (!fs.existsSync(shimPath) || fs.readFileSync(shimPath, 'utf8') !== shimBody) {
        fs.writeFileSync(shimPath, shimBody, 'utf8');
        fs.chmodSync(shimPath, 0o755);
    }
    if (!fs.existsSync(cmdShimPath) || fs.readFileSync(cmdShimPath, 'utf8') !== cmdShimBody) {
        fs.writeFileSync(cmdShimPath, cmdShimBody, 'utf8');
    }

    return shimDir;
}

function buildPnpmShimBody(candidate) {
    switch (candidate.command) {
        case 'corepack':
            return '#!/usr/bin/env sh\nexec corepack pnpm "$@"\n';
        case 'bun':
            return '#!/usr/bin/env sh\nexec bun x pnpm "$@"\n';
        default:
            throw new Error(`Unsupported pnpm shim candidate: ${candidate.command}`);
    }
}

function buildPnpmCmdShimBody(candidate) {
    switch (candidate.command) {
        case 'corepack':
            return '@echo off\r\ncorepack pnpm %*\r\n';
        case 'bun':
            return '@echo off\r\nbun x pnpm %*\r\n';
        default:
            throw new Error(`Unsupported pnpm shim candidate: ${candidate.command}`);
    }
}

function prependToPath(env, entry) {
    const nextEnv = normalizePathEnv(env);
    nextEnv.PATH = nextEnv.PATH ? `${entry}${path.delimiter}${nextEnv.PATH}` : entry;
    const pathKey = Object.keys(nextEnv).find((key) => key.toLowerCase() === 'path' && key !== 'PATH');
    if (pathKey) {
        nextEnv[pathKey] = nextEnv.PATH;
    }
    return nextEnv;
}

function normalizePathEnv(env) {
    const nextEnv = { ...env };
    const pathKey = Object.keys(nextEnv).find((key) => key.toLowerCase() === 'path');
    if (pathKey && pathKey !== 'PATH' && nextEnv.PATH === undefined) {
        nextEnv.PATH = nextEnv[pathKey];
    }
    if (pathKey && pathKey !== 'PATH' && nextEnv.PATH !== undefined) {
        nextEnv[pathKey] = nextEnv.PATH;
    }
    return nextEnv;
}

module.exports = {
    PACKAGE_MANAGER_SHIM_DIR_NAME,
    buildPackageManagerRuntime,
    packageManagerCandidates
};