import { execFile } from 'node:child_process';
import { promisify } from 'node:util';
import { existsSync } from 'node:fs';
import { delimiter } from 'node:path';
import path from 'node:path';

const execFileP = promisify(execFile);

// Per-agent model picker.
//
//   - `listModels`         : optional spec for fetching the model list from
//                            the CLI itself ({ args, parse, timeoutMs }).
//                            When defined we run it during agent detection
//                            (best-effort, with a timeout) and use the
//                            result. If the listing fails we fall back to
//                            `fallbackModels` so the UI still has something
//                            to show.
//   - `fallbackModels`     : static hint list. Used as the source of truth
//                            for CLIs that don't expose a listing command
//                            (Claude Code, Codex, Gemini CLI, Qwen Code)
//                            and as the fallback for the others.
//   - `reasoningOptions`   : optional reasoning-effort presets (currently
//                            only Codex exposes this knob).
//   - `buildArgs(prompt, imagePaths, extraAllowedDirs, options)` returns
//     argv for the child process. `options = { model, reasoning }` carries
//     whatever the user picked in the model menu — agents that don't take a
//     model flag ignore them.
//
// Every model list is prefixed with a synthetic `'default'` entry meaning
// "let the CLI pick" — the agent runs with no `--model` flag, so the
// user's local CLI config wins.
//
// `extraAllowedDirs` is a list of absolute directories the agent must be
// permitted to read files from (skill seeds, design-system specs) that live
// outside the project cwd. Currently only Claude Code wires this through
// (`--add-dir`); other agents either inherit broader access or run with cwd
// boundaries we can't widen via flags.
//
// `streamFormat` hints to the daemon how to interpret stdout:
//   - 'claude-stream-json' : line-delimited JSON emitted by Claude Code's
//     `--output-format stream-json`. Daemon parses it into typed events
//     (text / thinking / tool_use / tool_result / status) for the UI.
//   - 'plain' (default)    : raw text, forwarded chunk-by-chunk.

const DEFAULT_MODEL_OPTION = { id: 'default', label: 'Default (CLI config)' };

// Parse one-id-per-line stdout from `<cli> models` and prepend the synthetic
// default option. Used by opencode / cursor-agent.
function parseLineSeparatedModels(stdout) {
  const ids = String(stdout || '')
    .split('\n')
    .map((line) => line.trim())
    .filter((line) => line.length > 0 && !line.startsWith('#'));
  // De-dupe while preserving order — some CLIs print near-duplicates.
  const seen = new Set();
  const out = [DEFAULT_MODEL_OPTION];
  for (const id of ids) {
    if (seen.has(id)) continue;
    seen.add(id);
    out.push({ id, label: id });
  }
  return out;
}

export const AGENT_DEFS = [
  {
    id: 'claude',
    name: 'Claude Code',
    bin: 'claude',
    versionArgs: ['--version'],
    // `claude` has no list-models subcommand; the CLI accepts both short
    // aliases (sonnet/opus/haiku) and the full ids, so we ship both as
    // hints. Users who want a non-shipped model can paste it via the
    // Settings dialog's custom-model input.
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'sonnet', label: 'Sonnet (alias)' },
      { id: 'opus', label: 'Opus (alias)' },
      { id: 'haiku', label: 'Haiku (alias)' },
      { id: 'claude-opus-4-5', label: 'claude-opus-4-5' },
      { id: 'claude-sonnet-4-5', label: 'claude-sonnet-4-5' },
      { id: 'claude-haiku-4-5', label: 'claude-haiku-4-5' },
    ],
    buildArgs: (prompt, _imagePaths, extraAllowedDirs = [], options = {}) => {
      const args = [
        '-p',
        prompt,
        '--output-format',
        'stream-json',
        '--verbose',
        '--include-partial-messages',
      ];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      const dirs = (extraAllowedDirs || []).filter(
        (d) => typeof d === 'string' && d.length > 0,
      );
      if (dirs.length > 0) {
        args.push('--add-dir', ...dirs);
      }
      return args;
    },
    streamFormat: 'claude-stream-json',
  },
  {
    id: 'codex',
    name: 'Codex CLI',
    bin: 'codex',
    versionArgs: ['--version'],
    // Codex doesn't have a `models` subcommand; ship the most common ids
    // as a hint. Users can supply other ids via the custom-model input.
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'gpt-5-codex', label: 'gpt-5-codex' },
      { id: 'gpt-5', label: 'gpt-5' },
      { id: 'o3', label: 'o3' },
      { id: 'o4-mini', label: 'o4-mini' },
    ],
    reasoningOptions: [
      { id: 'default', label: 'Default' },
      { id: 'minimal', label: 'Minimal' },
      { id: 'low', label: 'Low' },
      { id: 'medium', label: 'Medium' },
      { id: 'high', label: 'High' },
    ],
    buildArgs: (prompt, _imagePaths, _extra, options = {}) => {
      const args = ['exec'];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      if (options.reasoning && options.reasoning !== 'default') {
        // Codex accepts `-c key=value` config overrides; reasoning effort
        // is exposed as `model_reasoning_effort`.
        args.push('-c', `model_reasoning_effort="${options.reasoning}"`);
      }
      args.push(prompt);
      return args;
    },
    streamFormat: 'plain',
  },
  {
    id: 'gemini',
    name: 'Gemini CLI',
    bin: 'gemini',
    versionArgs: ['--version'],
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'gemini-2.5-pro', label: 'gemini-2.5-pro' },
      { id: 'gemini-2.5-flash', label: 'gemini-2.5-flash' },
    ],
    buildArgs: (prompt, _imagePaths, _extra, options = {}) => {
      const args = [];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      args.push('-p', prompt);
      return args;
    },
    streamFormat: 'plain',
  },
  {
    id: 'opencode',
    name: 'OpenCode',
    bin: 'opencode',
    versionArgs: ['--version'],
    // `opencode models` prints `provider/model` per line.
    listModels: {
      args: ['models'],
      parse: parseLineSeparatedModels,
      timeoutMs: 8000,
    },
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'anthropic/claude-sonnet-4-5', label: 'anthropic/claude-sonnet-4-5' },
      { id: 'openai/gpt-5', label: 'openai/gpt-5' },
      { id: 'google/gemini-2.5-pro', label: 'google/gemini-2.5-pro' },
    ],
    buildArgs: (prompt, _imagePaths, _extra, options = {}) => {
      const args = ['run'];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      args.push(prompt);
      return args;
    },
    streamFormat: 'plain',
  },
  {
    id: 'cursor-agent',
    name: 'Cursor Agent',
    bin: 'cursor-agent',
    versionArgs: ['--version'],
    // `cursor-agent models` prints account-bound model ids per line. When
    // the user isn't authed it prints "No models available for this
    // account." — that's not a model list, so we detect it and fall back.
    listModels: {
      args: ['models'],
      timeoutMs: 5000,
      parse: (stdout) => {
        const trimmed = String(stdout || '').trim();
        if (!trimmed || /no models available/i.test(trimmed)) return null;
        return parseLineSeparatedModels(trimmed);
      },
    },
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'auto', label: 'auto' },
      { id: 'sonnet-4', label: 'sonnet-4' },
      { id: 'sonnet-4-thinking', label: 'sonnet-4-thinking' },
      { id: 'gpt-5', label: 'gpt-5' },
    ],
    buildArgs: (prompt, _imagePaths, _extra, options = {}) => {
      const args = [];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      args.push('-p', prompt);
      return args;
    },
    streamFormat: 'plain',
  },
  {
    id: 'qwen',
    name: 'Qwen Code',
    bin: 'qwen',
    versionArgs: ['--version'],
    fallbackModels: [
      DEFAULT_MODEL_OPTION,
      { id: 'qwen3-coder-plus', label: 'qwen3-coder-plus' },
      { id: 'qwen3-coder-flash', label: 'qwen3-coder-flash' },
    ],
    buildArgs: (prompt, _imagePaths, _extra, options = {}) => {
      const args = [];
      if (options.model && options.model !== 'default') {
        args.push('--model', options.model);
      }
      args.push('-p', prompt);
      return args;
    },
    streamFormat: 'plain',
  },
];

function resolveOnPath(bin) {
  const exts =
    process.platform === 'win32'
      ? (process.env.PATHEXT || '.EXE;.CMD;.BAT').split(';')
      : [''];
  const dirs = (process.env.PATH || '').split(delimiter);
  for (const dir of dirs) {
    for (const ext of exts) {
      const full = path.join(dir, bin + ext);
      if (full && existsSync(full)) return full;
    }
  }
  return null;
}

async function fetchModels(def, resolvedBin) {
  if (!def.listModels) return def.fallbackModels;
  try {
    const { stdout } = await execFileP(resolvedBin, def.listModels.args, {
      timeout: def.listModels.timeoutMs ?? 5000,
      // Models lists from popular CLIs (e.g. opencode) easily exceed the
      // default 1MB buffer once you include every openrouter model. Bump
      // it so we don't truncate the listing.
      maxBuffer: 8 * 1024 * 1024,
    });
    const parsed = def.listModels.parse(stdout);
    // Empty / null parse result means the CLI didn't actually return a
    // usable list (e.g. cursor-agent's "No models available"); fall back
    // to the static hint so the picker isn't stuck on Default-only.
    if (!parsed || parsed.length === 0) return def.fallbackModels;
    return parsed;
  } catch {
    return def.fallbackModels;
  }
}

async function probe(def) {
  const resolved = resolveOnPath(def.bin);
  if (!resolved) {
    return {
      ...stripFns(def),
      models: def.fallbackModels ?? [DEFAULT_MODEL_OPTION],
      available: false,
    };
  }
  let version = null;
  try {
    const { stdout } = await execFileP(resolved, def.versionArgs, { timeout: 3000 });
    version = stdout.trim().split('\n')[0];
  } catch {
    // binary exists but --version failed; still mark available
  }
  const models = await fetchModels(def, resolved);
  return {
    ...stripFns(def),
    models,
    available: true,
    path: resolved,
    version,
  };
}

function stripFns(def) {
  // Drop the buildArgs / listModels closures but keep declarative metadata
  // (reasoningOptions, streamFormat, name, bin, etc.). `models` is
  // populated separately by `fetchModels`, so we strip the static
  // `fallbackModels` slot here too.
  const { buildArgs, listModels, fallbackModels, ...rest } = def;
  return rest;
}

export async function detectAgents() {
  const results = await Promise.all(AGENT_DEFS.map(probe));
  // Refresh the validation cache from whatever we just surfaced to the UI
  // so /api/chat can accept any model the user could have just picked,
  // including ones that only showed up after a CLI re-auth.
  for (const agent of results) {
    rememberLiveModels(agent.id, agent.models);
  }
  return results;
}

export function getAgentDef(id) {
  return AGENT_DEFS.find((a) => a.id === id) || null;
}

// Daemon's /api/chat needs to validate the user's model pick against the
// list we last surfaced to the UI. We keep a per-agent cache of the most
// recent live list (refreshed every detectAgents() call) and additionally
// trust any value present in the static fallback. A model that's neither
// gets rejected so a stale or hostile value can't smuggle arbitrary flags.
const liveModelCache = new Map();

export function rememberLiveModels(agentId, models) {
  if (!Array.isArray(models)) return;
  liveModelCache.set(
    agentId,
    new Set(models.map((m) => m && m.id).filter((id) => typeof id === 'string')),
  );
}

export function isKnownModel(def, modelId) {
  if (!modelId) return false;
  const live = liveModelCache.get(def.id);
  if (live && live.has(modelId)) return true;
  if (Array.isArray(def.fallbackModels)) {
    return def.fallbackModels.some((m) => m.id === modelId);
  }
  return false;
}

// Permit user-typed model ids that didn't appear in either the live
// listing or the static fallback (e.g. the user is on a brand-new model
// the CLI's `models` command hasn't surfaced yet). The CLI gets the value
// as a child-process arg — not a shell string — so injection isn't a
// concern, but we still reject anything that could be misread as a flag
// by a downstream CLI or that contains whitespace / control chars.
export function sanitizeCustomModel(id) {
  if (typeof id !== 'string') return null;
  const trimmed = id.trim();
  if (trimmed.length === 0 || trimmed.length > 200) return null;
  if (!/^[A-Za-z0-9][A-Za-z0-9._/:@-]*$/.test(trimmed)) return null;
  return trimmed;
}