/**
 * Git exec argument validation for the relay's git.exec handler.
 *
 * Why: oxlint max-lines requires files to stay under 300 lines.
 * Extracted from git-handler-ops.ts to keep both files under the limit.
 */

// Why: only read-only git subcommands are allowed via exec. config is restricted
// to read-only flags; branch rejects destructive flags; fetch/worktree removed.
const ALLOWED_GIT_SUBCOMMANDS = new Set([
  'rev-parse',
  'branch',
  'log',
  'show-ref',
  'ls-remote',
  'remote',
  'symbolic-ref',
  'merge-base',
  'diff',
  'ls-files',
  'for-each-ref',
  'check-ref-format',
  'config'
])
const CONFIG_READ_ONLY_FLAGS = new Set(['--get', '--get-all', '--list', '--get-regexp', '-l'])
// Why: checking presence of a read-only flag is insufficient — a request could
// include both --list (passes the check) and --add (performs a write). Reject
// known write operations explicitly.
const CONFIG_WRITE_FLAGS = new Set([
  '--add',
  '--unset',
  '--unset-all',
  '--replace-all',
  '--rename-section',
  '--remove-section',
  '--edit',
  '-e',
  // Why: --file redirects config reads to an arbitrary file, enabling path
  // traversal (e.g. `--file /etc/passwd --list` leaks file contents).
  '--file',
  '-f',
  '--global',
  '--system'
])
const BRANCH_DESTRUCTIVE_FLAGS = new Set([
  '-d',
  '-D',
  '--delete',
  '-m',
  '-M',
  '--move',
  '-c',
  '-C',
  '--copy'
])

// Why: these flags are dangerous across ALL subcommands — --output writes to
// arbitrary paths, --exec-path changes where git loads helpers from, --work-tree
// and --git-dir escape the validated worktree.
const GLOBAL_DENIED_FLAGS = new Set(['--output', '-o', '--exec-path', '--work-tree', '--git-dir'])

const REMOTE_WRITE_SUBCOMMANDS = new Set([
  'add',
  'remove',
  'rm',
  'rename',
  'set-head',
  'set-branches',
  'set-url',
  'prune',
  'update'
])
const SYMBOLIC_REF_WRITE_FLAGS = new Set(['-d', '--delete', '-m'])
const DIFF_ALLOWED_FLAGS = new Set([
  '--cached',
  '--staged',
  '--name-status',
  '--patch',
  '--minimal',
  '--no-color',
  '--no-ext-diff'
])

// Why: git accepts --flag=value compound syntax (e.g. --file=/etc/passwd),
// which bypasses exact-match Set.has() checks. This helper catches both forms.
function matchesDeniedFlag(arg: string, denySet: Set<string>): boolean {
  if (denySet.has(arg)) {
    return true
  }
  const eqIdx = arg.indexOf('=')
  if (eqIdx > 0) {
    return denySet.has(arg.slice(0, eqIdx))
  }
  return false
}

export function validateGitExecArgs(args: string[]): void {
  // Why: git accepts `-c key=value` before the subcommand, which can override
  // config and execute arbitrary commands (e.g. core.sshCommand). Reject any
  // arguments before the subcommand that look like global git flags.
  let subcommandIdx = 0
  while (subcommandIdx < args.length && args[subcommandIdx].startsWith('-')) {
    subcommandIdx++
  }
  if (subcommandIdx > 0) {
    throw new Error('Global git flags before the subcommand are not allowed')
  }

  const subcommand = args[0]
  if (!subcommand || !ALLOWED_GIT_SUBCOMMANDS.has(subcommand)) {
    throw new Error(`git subcommand not allowed: ${subcommand ?? '(empty)'}`)
  }
  const restArgs = args.slice(1)

  if (restArgs.some((a) => matchesDeniedFlag(a, GLOBAL_DENIED_FLAGS))) {
    throw new Error('Dangerous git flags are not allowed via exec')
  }

  if (subcommand === 'config') {
    if (!restArgs.some((a) => CONFIG_READ_ONLY_FLAGS.has(a))) {
      throw new Error('git config is restricted to read-only operations (--get, --list, etc.)')
    }
    if (restArgs.some((a) => matchesDeniedFlag(a, CONFIG_WRITE_FLAGS))) {
      throw new Error('git config write operations are not allowed via exec')
    }
  }
  if (subcommand === 'branch') {
    if (restArgs.some((a) => matchesDeniedFlag(a, BRANCH_DESTRUCTIVE_FLAGS))) {
      throw new Error('Destructive git branch flags are not allowed via exec')
    }
  }
  if (subcommand === 'remote') {
    const remoteSubcmd = restArgs.find((a) => !a.startsWith('-'))
    if (remoteSubcmd && REMOTE_WRITE_SUBCOMMANDS.has(remoteSubcmd)) {
      throw new Error('Destructive git remote operations are not allowed via exec')
    }
  }
  if (subcommand === 'symbolic-ref') {
    if (restArgs.some((a) => matchesDeniedFlag(a, SYMBOLIC_REF_WRITE_FLAGS))) {
      throw new Error('git symbolic-ref write operations are not allowed via exec')
    }
    const positionalArgs = restArgs.filter((a) => !a.startsWith('-'))
    if (positionalArgs.length >= 2) {
      throw new Error('git symbolic-ref write operations are not allowed via exec')
    }
  }
  if (subcommand === 'diff') {
    // Why: SSH commit-message generation only needs read-only staged diffs.
    // Keep this narrow so `git.exec` cannot become a general file reader via
    // arbitrary revisions, pathspecs, or --no-index.
    if (!restArgs.some((a) => a === '--cached' || a === '--staged')) {
      throw new Error('git diff via exec is restricted to staged changes')
    }
    const unsupportedArg = restArgs.find((a) => !DIFF_ALLOWED_FLAGS.has(a))
    if (unsupportedArg) {
      throw new Error(`git diff flag not allowed via exec: ${unsupportedArg}`)
    }
  }
}