/**
 * Codex Link ("Codex Bağlama") — decisions and side effects.
 *
 * When the feature is on and OpenAI Codex is installed on this machine, the IDE
 * runs a small local Python bridge, points Codex's `config.toml` at it and
 * registers the bridge as a login item, so Codex keeps working with the IDE's
 * models while the IDE itself is closed. Turning it off undoes all three.
 *
 * Ordering is the safety property: Codex cannot work at all while its config
 * points at a dead address, so the config line is written only AFTER the bridge
 * has answered, and it is taken back out if the bridge cannot be brought up.
 *
 * Electron-free on purpose. `createCodexLink` takes every effect as a
 * dependency (files, spawn, HTTP, registry) so the ordering above is provable
 * in a unit test; `createNodeCodexLinkDeps` is the real wiring main.ts uses.
 * The text transformations live in `codex-link-config.ts`.
 */

import { execFile, spawn } from 'node:child_process'
import fs from 'node:fs'
import path from 'node:path'

import {
  addCodexLinkLine,
  CODEX_BRIDGE_VERSION,
  CODEX_LINK_LAUNCHER_NAME,
  CODEX_LINK_REFRESH_URL,
  CODEX_LINK_RUN_KEY,
  CODEX_LINK_RUN_VALUE,
  CODEX_LINK_STATUS_URL,
  CODEX_LINK_STOP_URL,
  codexAutostartPlan,
  codexBridgeArgs,
  type CodexBridgeLaunch,
  inspectCodexConfig,
  parseCodexLinkSettings,
  removeCodexLinkLine,
  serializeCodexBridgeConfig,
  serializeCodexLinkSettings
} from './codex-link-config'
import type { CodexLinkError, CodexLinkIdeState, CodexLinkPatch, CodexLinkStatus } from './codex-link-types'
import { hiddenWindowsChildOptions } from './windows-child-options'

export type { CodexLinkError, CodexLinkIdeState, CodexLinkPatch, CodexLinkStatus } from './codex-link-types'

export interface CodexLinkPaths {
  /** `<data root>/codex-baglama.json` */
  settingsFile: string
  /** `<data root>/codex-bridge` — the bridge's data folder. */
  bridgeHome: string
  hermesHome: string
  /** `<resources>/codex-bridge/bridge.py` */
  bridgeScript: string
  /** Windowless interpreter, preferred. */
  pythonw: string
  /** Console interpreter, used hidden when pythonw is absent. */
  python: string
  /** `<CODEX_HOME or ~/.codex>/config.toml` */
  codexConfig: string
}

export interface CodexLinkDeps {
  paths: CodexLinkPaths
  exists: (file: string) => boolean
  /** null when the file is missing; throws when it cannot be read losslessly. */
  readText: (file: string) => null | string
  /** tmp + rename; creates the parent folder. */
  writeTextAtomic: (file: string, text: string) => void
  /** Start the bridge detached and hidden; it must outlive the IDE. */
  spawnBridge: (command: string, args: string[], env: Record<string, string>) => void
  /** Parsed JSON body, or null when nothing answered within `budgetMs`. */
  request: (method: 'GET' | 'POST', url: string, budgetMs: number) => Promise<unknown>
  setAutostart: (command: string) => Promise<void>
  clearAutostart: () => Promise<void>
  sleep: (ms: number) => Promise<void>
  now: () => number
  log: (message: string) => void
}

// The single wait this feature owns: how long a freshly spawned bridge gets to
// answer its status endpoint before the apply gives up.
export const CODEX_BRIDGE_START_BUDGET_MS = 45_000
const START_POLL_INTERVAL_MS = 500
// A probe of an already-running (or absent) local bridge. Loopback answers or
// refuses at once; the bound only keeps Settings from hanging on a wedged port.
const PROBE_BUDGET_MS = 2_000

interface BridgeProbe {
  ideDurum: CodexLinkIdeState | null
  ideModel: null | number
  ozet: boolean | null
  running: boolean
  surum: null | string
}

const NOT_RUNNING: BridgeProbe = { ideDurum: null, ideModel: null, ozet: null, running: false, surum: null }

function readProbe(body: unknown): BridgeProbe {
  if (!body || typeof body !== 'object' || (body as { ok?: unknown }).ok !== true) {
    return NOT_RUNNING
  }

  const reply = body as { ide_durum?: unknown; ide_model?: unknown; ozet?: unknown; surum?: unknown }
  const state = reply.ide_durum

  return {
    ideDurum: state === 'tamam' || state === 'kapali' || state === 'anahtar-yok' ? state : null,
    ideModel: typeof reply.ide_model === 'number' && Number.isFinite(reply.ide_model) ? reply.ide_model : null,
    ozet: typeof reply.ozet === 'boolean' ? reply.ozet : null,
    running: true,
    surum: typeof reply.surum === 'string' ? reply.surum : null
  }
}

function describe(error: unknown): string {
  return error instanceof Error ? error.message : String(error)
}

export interface CodexLink {
  /** Side-effect free: reads the preference, the files and the status endpoint. */
  getStatus: () => Promise<CodexLinkStatus>
  /** Persist `patch.enabled` (if given), make the machine match, report. */
  apply: (patch?: CodexLinkPatch) => Promise<CodexLinkStatus>
}

export function createCodexLink(deps: CodexLinkDeps): CodexLink {
  const { paths } = deps
  let lastError: CodexLinkError | null = null
  let queue: Promise<unknown> = Promise.resolve()

  const launch: CodexBridgeLaunch = {
    bridgeHome: paths.bridgeHome,
    bridgeScript: paths.bridgeScript,
    hermesHome: paths.hermesHome
  }

  const fail = (code: CodexLinkError, error?: unknown) => {
    lastError = code
    deps.log(`[codex-link] ${code}${error === undefined ? '' : `: ${describe(error)}`}`)
  }

  const readSettings = () => {
    try {
      return parseCodexLinkSettings(deps.readText(paths.settingsFile))
    } catch {
      return parseCodexLinkSettings(null)
    }
  }

  // The interpreter to run the bridge with, or null while the IDE's own
  // first-run setup has not produced the venv yet.
  const interpreter = () =>
    deps.exists(paths.pythonw) ? paths.pythonw : deps.exists(paths.python) ? paths.python : null

  // The owner of Codex's base URL. An unreadable config counts as foreign for
  // the purpose of "do not touch": we only edit what we could read back intact.
  const readCodexConfig = (): { found: boolean; owner: 'absent' | 'foreign' | 'ours'; text: null | string } => {
    if (!deps.exists(paths.codexConfig)) {
      return { found: false, owner: 'absent', text: null }
    }

    try {
      const text = deps.readText(paths.codexConfig)

      return text === null
        ? { found: false, owner: 'absent', text: null }
        : { found: true, owner: inspectCodexConfig(text), text }
    } catch (error) {
      deps.log(`[codex-link] config.toml could not be read: ${describe(error)}`)

      return { found: true, owner: 'foreign', text: null }
    }
  }

  const probe = async (budgetMs = PROBE_BUDGET_MS): Promise<BridgeProbe> => {
    try {
      return readProbe(await deps.request('GET', CODEX_LINK_STATUS_URL, budgetMs))
    } catch {
      return NOT_RUNNING
    }
  }

  const statusFrom = (
    enabled: boolean,
    config: { found: boolean; owner: string },
    bridge: BridgeProbe
  ): CodexLinkStatus => ({
    enabled,
    codexFound: config.found,
    venvReady: interpreter() !== null,
    foreign: config.owner === 'foreign',
    bridgeRunning: bridge.running,
    ideDurum: bridge.ideDurum,
    ideModel: bridge.ideModel,
    ozet: bridge.ozet,
    lastError
  })

  const removeOurLine = (text: null | string): boolean => {
    if (text === null) {
      return true
    }

    const edit = removeCodexLinkLine(text)

    if (!edit.changed) {
      return true
    }

    try {
      deps.writeTextAtomic(paths.codexConfig, edit.text)

      return true
    } catch (error) {
      fail('config-write-failed', error)

      return false
    }
  }

  // Off: take back everything we put there. Each step is independent — a
  // failure in one must not leave the others in place.
  const tearDown = async (config: ReturnType<typeof readCodexConfig>): Promise<BridgeProbe> => {
    removeOurLine(config.text)

    try {
      await deps.clearAutostart()
    } catch (error) {
      fail('autostart-failed', error)
    }

    // A foreign config means whatever listens on the port serves someone
    // else's setup; stopping it would break a bridge we do not own.
    if (config.owner === 'foreign') {
      return probe()
    }

    try {
      // No answer means nothing of ours is listening; leave it alone.
      return (await deps.request('POST', CODEX_LINK_STOP_URL, PROBE_BUDGET_MS)) === null ? probe() : NOT_RUNNING
    } catch {
      return probe()
    }
  }

  const startBridge = async (python: string): Promise<BridgeProbe> => {
    try {
      deps.spawnBridge(python, codexBridgeArgs(launch), {
        AITURK_CODEX_BRIDGE_HOME: paths.bridgeHome,
        HERMES_HOME: paths.hermesHome
      })
    } catch (error) {
      deps.log(`[codex-link] bridge spawn failed: ${describe(error)}`)

      return NOT_RUNNING
    }

    const deadline = deps.now() + CODEX_BRIDGE_START_BUDGET_MS

    for (;;) {
      const remaining = deadline - deps.now()

      if (remaining <= 0) {
        return NOT_RUNNING
      }

      const result = await probe(Math.min(PROBE_BUDGET_MS, remaining))

      if (result.running) {
        return result
      }

      await deps.sleep(Math.min(START_POLL_INTERVAL_MS, Math.max(0, deadline - deps.now())))
    }
  }

  // On: bridge.json → bridge up (verified) → config.toml → login item.
  const setUp = async (python: string, config: ReturnType<typeof readCodexConfig>): Promise<BridgeProbe> => {
    if (!deps.exists(paths.bridgeScript)) {
      fail('bridge-missing', paths.bridgeScript)

      return probe()
    }

    try {
      deps.writeTextAtomic(path.join(paths.bridgeHome, 'bridge.json'), serializeCodexBridgeConfig())
    } catch (error) {
      fail('bridge-config-failed', error)

      return probe()
    }

    let bridge = await probe()

    if (bridge.running && bridge.surum !== CODEX_BRIDGE_VERSION) {
      // A bridge from an older IDE build is still listening: replace it.
      try {
        await deps.request('POST', CODEX_LINK_STOP_URL, PROBE_BUDGET_MS)
      } catch {
        // It stops answering once it exits; the start below verifies the new one.
      }

      await deps.sleep(START_POLL_INTERVAL_MS * 2)
      bridge = NOT_RUNNING
    }

    if (bridge.running) {
      // Already up: have it re-read the IDE session and model list now (a sign-in
      // since its last periodic refresh would otherwise show up minutes later).
      try {
        const refreshed = readProbe(await deps.request('POST', CODEX_LINK_REFRESH_URL, CODEX_BRIDGE_START_BUDGET_MS))

        bridge = refreshed.running ? refreshed : bridge
      } catch {
        // The status it already gave stays valid.
      }
    } else {
      bridge = await startBridge(python)
    }

    if (!bridge.running) {
      fail('bridge-start-failed')
      // Fail open: a line left over from an earlier run would now point Codex
      // at a dead address. Without it Codex simply talks to OpenAI directly.
      removeOurLine(config.text)

      return bridge
    }

    const edit = addCodexLinkLine(config.text ?? '')

    if (edit.changed) {
      try {
        deps.writeTextAtomic(paths.codexConfig, edit.text)
      } catch (error) {
        fail('config-write-failed', error)

        return bridge
      }
    }

    // Rewritten on every apply: an IDE update can move the bridge script.
    try {
      const plan = codexAutostartPlan(python, launch, path.join(paths.bridgeHome, CODEX_LINK_LAUNCHER_NAME))

      if (!plan) {
        throw new Error('the bridge command does not fit a Run value')
      }

      if (plan.launcher) {
        deps.writeTextAtomic(plan.launcher.path, plan.launcher.source)
      }

      await deps.setAutostart(plan.command)
    } catch (error) {
      fail('autostart-failed', error)
    }

    return bridge
  }

  const run = async (patch?: CodexLinkPatch): Promise<CodexLinkStatus> => {
    lastError = null

    if (typeof patch?.enabled === 'boolean') {
      try {
        deps.writeTextAtomic(paths.settingsFile, serializeCodexLinkSettings(readSettings().stored, patch.enabled))
      } catch (error) {
        // The preference did not stick, so do not act on it either: what the
        // machine does must match what the file says after a restart.
        fail('settings-write-failed', error)
      }
    }

    const { enabled } = readSettings()
    const config = readCodexConfig()

    if (!enabled) {
      return statusFrom(enabled, config, await tearDown(config))
    }

    const python = interpreter()

    if (!config.found || !python || config.owner === 'foreign') {
      return statusFrom(enabled, config, await probe())
    }

    return statusFrom(enabled, config, await setUp(python, config))
  }

  return {
    getStatus: async () => statusFrom(readSettings().enabled, readCodexConfig(), await probe()),
    // One apply at a time: two interleaved runs could write the config line
    // from one while the other is tearing the bridge down.
    apply: patch => {
      const next = queue.then(() => run(patch))
      queue = next.catch(() => undefined)

      return next
    }
  }
}

// ── Real dependencies ───────────────────────────────────────────────────────

function writeTextAtomic(file: string, text: string): void {
  fs.mkdirSync(path.dirname(file), { recursive: true })
  const tmp = `${file}.${process.pid}.tmp`

  try {
    fs.writeFileSync(tmp, text, 'utf8')
    fs.renameSync(tmp, file)
  } catch (error) {
    fs.rmSync(tmp, { force: true })

    throw error
  }
}

// Decode as UTF-8 and insist the bytes survive the round trip. A config in
// another encoding would be corrupted by a rewrite, so refuse to return it.
function readTextLossless(file: string): null | string {
  let bytes: Buffer

  try {
    bytes = fs.readFileSync(file)
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
      return null
    }

    throw error
  }

  const text = bytes.toString('utf8')

  if (!Buffer.from(text, 'utf8').equals(bytes)) {
    throw new Error('file is not valid UTF-8')
  }

  return text
}

function runReg(args: string[]): Promise<{ code: number; stderr: string }> {
  const reg = path.join(process.env.SystemRoot || 'C:\\Windows', 'System32', 'reg.exe')

  return new Promise(resolve => {
    execFile(reg, args, hiddenWindowsChildOptions({ encoding: 'utf8' }), (error, _stdout, stderr) => {
      const exit = error ? (typeof (error as { code?: unknown }).code === 'number' ? (error as any).code : 1) : 0
      resolve({ code: exit, stderr: String(stderr || (error ? error.message : '')).trim() })
    })
  })
}

async function requestJson(method: 'GET' | 'POST', url: string, budgetMs: number): Promise<unknown> {
  try {
    const response = await fetch(url, { method, signal: AbortSignal.timeout(Math.max(1, budgetMs)) })

    return response.ok ? await response.json() : null
  } catch {
    return null
  }
}

export function createNodeCodexLinkDeps(paths: CodexLinkPaths, log: (message: string) => void): CodexLinkDeps {
  return {
    paths,
    exists: file => fs.existsSync(file),
    readText: readTextLossless,
    writeTextAtomic,
    spawnBridge: (command, args, env) => {
      fs.mkdirSync(paths.bridgeHome, { recursive: true })

      // Detached with no stdio and unref'd: the bridge is deliberately NOT a
      // child the IDE cleans up on quit — Codex depends on it staying alive.
      const child = spawn(
        command,
        args,
        hiddenWindowsChildOptions({
          cwd: paths.bridgeHome,
          detached: true,
          env: { ...process.env, ...env },
          stdio: 'ignore'
        }) as any
      )

      child.on('error', error => log(`[codex-link] bridge process error: ${error.message}`))
      child.unref()
    },
    request: requestJson,
    setAutostart: async command => {
      const result = await runReg([
        'add',
        CODEX_LINK_RUN_KEY,
        '/v',
        CODEX_LINK_RUN_VALUE,
        '/t',
        'REG_SZ',
        '/d',
        command,
        '/f'
      ])

      if (result.code !== 0) {
        throw new Error(`reg add exited ${result.code}: ${result.stderr}`)
      }
    },
    clearAutostart: async () => {
      // `reg delete` fails on a value that is not there; absent is already the
      // state we want, so look first.
      const present = await runReg(['query', CODEX_LINK_RUN_KEY, '/v', CODEX_LINK_RUN_VALUE])

      if (present.code !== 0) {
        return
      }

      const result = await runReg(['delete', CODEX_LINK_RUN_KEY, '/v', CODEX_LINK_RUN_VALUE, '/f'])

      if (result.code !== 0) {
        throw new Error(`reg delete exited ${result.code}: ${result.stderr}`)
      }
    },
    sleep: ms => new Promise(resolve => setTimeout(resolve, ms)),
    now: () => Date.now(),
    log
  }
}