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

let vscode;
try {
  vscode = require('vscode');
} catch (_) {
  vscode = undefined;
}

function requireVscode() {
  if (!vscode) {
    throw new Error('VS Code API is only available inside VS Code');
  }
  return vscode;
}

function activate(context) {
  const api = requireVscode();
  context.subscriptions.push(
    api.commands.registerCommand('dosh.openRemote', openRemote),
    api.commands.registerCommand('dosh.configureHost', configureHostCommand),
    api.commands.registerCommand('dosh.showSshConfig', showSshConfig)
  );
}

async function openRemote() {
  const api = requireVscode();
  const configured = await configureHost();
  if (!configured) {
    return;
  }
  const remotePath = await api.window.showInputBox({
    title: 'Remote path',
    prompt: 'Path to open on the remote host',
    value: '~'
  });
  if (remotePath === undefined) {
    return;
  }
  const suffix = remotePath ? `/${remotePath.replace(/^\/+/, '')}` : '';
  await api.commands.executeCommand(
    'vscode.openFolder',
    api.Uri.parse(`vscode-remote://ssh-remote+${configured.alias}${suffix}`),
    { forceNewWindow: true }
  );
}

async function configureHostCommand() {
  const api = requireVscode();
  const configured = await configureHost();
  if (configured) {
    api.window.showInformationMessage(`Dosh Remote-SSH host ready: ${configured.alias}`);
  }
}

async function configureHost() {
  const api = requireVscode();
  const host = await api.window.showInputBox({
    title: 'Dosh host',
    prompt: 'Dosh host alias, e.g. palav',
    ignoreFocusOut: true
  });
  if (!host) {
    return undefined;
  }
  const user = await api.window.showInputBox({
    title: 'Remote SSH user',
    prompt: 'Optional. Leave blank to let SSH config decide.',
    ignoreFocusOut: true
  });
  const config = api.workspace.getConfiguration('dosh');
  const alias = `dosh-${safeAlias(host)}`;
  const block = sshBlock({
    alias,
    host,
    user: user || undefined,
    executable: config.get('executable') || 'dosh',
    targetHost: config.get('targetHost') || '127.0.0.1',
    targetPort: Number(config.get('targetPort') || 22),
    doshPort: Number(config.get('doshPort') || 0),
    platform: process.platform
  });
  const sshDir = path.join(os.homedir(), '.ssh');
  fs.mkdirSync(sshDir, { recursive: true });
  const mainConfig = path.join(sshDir, 'config');
  const generatedPath = resolveGeneratedSshConfigPath(
    mainConfig,
    config.get('generatedSshConfig') || path.join(sshDir, 'config.dosh'),
    os.homedir(),
    process.platform
  );
  ensureInclude(mainConfig, sshIncludeTarget(mainConfig, generatedPath, process.platform));
  upsertBlock(generatedPath, alias, block);
  return { alias, generatedPath };
}

function sshBlock(options) {
  const platform = options.platform || process.platform;
  let proxy = sshConfigWord(options.executable, platform);
  if (options.doshPort > 0) {
    proxy += ` --dosh-port ${options.doshPort}`;
  }
  proxy += ` proxy-stdio ${sshConfigWord(options.host, platform)} %h %p`;
  const lines = [
    `# BEGIN DOSH ${options.alias}`,
    `Host ${options.alias}`,
    `    HostName ${options.targetHost}`,
    `    Port ${options.targetPort}`,
    `    HostKeyAlias ${options.host}`,
    options.user ? `    User ${options.user}` : undefined,
    '    ClearAllForwardings yes',
    '    ServerAliveInterval 15',
    '    ServerAliveCountMax 3',
    `    ProxyCommand ${proxy}`,
    `# END DOSH ${options.alias}`,
    ''
  ].filter(Boolean);
  return lines.join('\n');
}

function ensureInclude(configPath, includeFile) {
  const dir = path.dirname(configPath);
  if (dir && dir !== '.') {
    fs.mkdirSync(dir, { recursive: true });
  }
  const raw = fs.existsSync(configPath) ? fs.readFileSync(configPath, 'utf8') : '';
  if (raw.split(/\r?\n/).some((line) => line.trim().toLowerCase() === `include ${includeFile}`.toLowerCase())) {
    return;
  }
  fs.writeFileSync(configPath, `Include ${includeFile}\n${raw ? `\n${raw}` : ''}`);
}

function sshIncludeTarget(mainConfigPath, generatedPath, platform = process.platform) {
  const pathApi = platform === 'win32' ? path.win32 : path;
  const mainDir = pathApi.resolve(pathApi.dirname(mainConfigPath));
  const generatedAbsolute = pathApi.resolve(mainDir, generatedPath);
  const generatedDir = pathApi.resolve(pathApi.dirname(generatedAbsolute));
  const includePath =
    normalizeCase(generatedDir, platform) === normalizeCase(mainDir, platform)
      ? pathApi.basename(generatedAbsolute)
      : generatedAbsolute;
  return sshConfigPathWord(includePath, platform);
}

function resolveGeneratedSshConfigPath(
  mainConfigPath,
  configuredPath,
  home = os.homedir(),
  platform = process.platform
) {
  const pathApi = platform === 'win32' ? path.win32 : path;
  const mainDir = pathApi.resolve(pathApi.dirname(mainConfigPath));
  const expanded = expandHomePath(configuredPath, home, platform);
  return pathApi.resolve(mainDir, expanded);
}

function upsertBlock(configPath, alias, block) {
  const dir = path.dirname(configPath);
  if (dir && dir !== '.') {
    fs.mkdirSync(dir, { recursive: true });
  }
  const raw = fs.existsSync(configPath) ? fs.readFileSync(configPath, 'utf8') : '';
  const begin = `# BEGIN DOSH ${alias}`;
  const end = `# END DOSH ${alias}`;
  const lines = raw.split(/\r?\n/);
  const out = [];
  let skipping = false;
  let replaced = false;
  for (const line of lines) {
    if (line.trim() === begin) {
      out.push(block.trimEnd());
      skipping = true;
      replaced = true;
      continue;
    }
    if (skipping) {
      if (line.trim() === end) {
        skipping = false;
      }
      continue;
    }
    if (line.length > 0 || out.length > 0) {
      out.push(line);
    }
  }
  if (!replaced) {
    if (out.length > 0 && out[out.length - 1] !== '') {
      out.push('');
    }
    out.push(block.trimEnd());
  }
  fs.writeFileSync(configPath, `${out.join('\n').trimEnd()}\n`);
}

async function showSshConfig() {
  const api = requireVscode();
  const config = api.workspace.getConfiguration('dosh');
  const sshDir = path.join(os.homedir(), '.ssh');
  const mainConfig = path.join(sshDir, 'config');
  const generatedPath = resolveGeneratedSshConfigPath(
    mainConfig,
    config.get('generatedSshConfig') || path.join(sshDir, 'config.dosh'),
    os.homedir(),
    process.platform
  );
  if (!fs.existsSync(generatedPath)) {
    api.window.showWarningMessage('No generated Dosh SSH config yet.');
    return;
  }
  const doc = await api.workspace.openTextDocument(generatedPath);
  await api.window.showTextDocument(doc);
}

function safeAlias(value) {
  const alias = value.replace(/[^a-zA-Z0-9_-]+/g, '-').replace(/^-+|-+$/g, '');
  return alias || 'host';
}

function shellQuote(value) {
  if (/^[a-zA-Z0-9_./:-]+$/.test(value)) {
    return value;
  }
  return `'${value.replace(/'/g, `'\\''`)}'`;
}

function sshConfigWord(value, platform = process.platform) {
  if (platform === 'win32') {
    return windowsCommandWord(value);
  }
  return shellQuote(value);
}

function sshConfigPathWord(value, platform = process.platform) {
  const normalized = platform === 'win32' ? value.replace(/\\/g, '/') : value;
  if (/^[a-zA-Z0-9_./:@%+=,-]+$/.test(normalized)) {
    return normalized;
  }
  return `"${normalized.replace(/["\\]/g, '\\$&')}"`;
}

function normalizeCase(value, platform) {
  return platform === 'win32' ? value.toLowerCase() : value;
}

function expandHomePath(value, home = os.homedir(), platform = process.platform) {
  if (value === '~') {
    return home;
  }
  if (value.startsWith('~/') || value.startsWith('~\\')) {
    const pathApi = platform === 'win32' ? path.win32 : path;
    return pathApi.join(home, value.slice(2));
  }
  return value;
}

function windowsCommandWord(value) {
  let out = '"';
  let backslashes = 0;
  for (const ch of value) {
    if (ch === '\\') {
      backslashes += 1;
      continue;
    }
    if (ch === '"') {
      out += '\\'.repeat(backslashes * 2 + 1);
      out += '"';
      backslashes = 0;
      continue;
    }
    out += '\\'.repeat(backslashes);
    backslashes = 0;
    out += ch;
  }
  out += '\\'.repeat(backslashes * 2);
  out += '"';
  return out;
}

function deactivate() {}

module.exports = {
  activate,
  deactivate,
  expandHomePath,
  ensureInclude,
  resolveGeneratedSshConfigPath,
  sshBlock,
  sshConfigPathWord,
  shellQuote,
  sshIncludeTarget,
  sshConfigWord,
  upsertBlock,
  windowsCommandWord
};