import { spawn as nodeSpawn } from 'node:child_process';
import { EventEmitter } from 'node:events';
import fs from 'node:fs/promises';
import path from 'node:path';

const CODE_EXECUTORS = new Set(['aider', 'openhands']);
const DEFAULT_STDIO_LIMIT = 64 * 1024;

function envFlag(value, fallback = false) {
  const raw = String(value ?? '').trim().toLowerCase();
  if (!raw) return fallback;
  return ['1', 'true', 'yes', 'on'].includes(raw);
}

function positiveInteger(value, fallback) {
  const n = Number(value);
  if (!Number.isFinite(n) || n <= 0) return fallback;
  return Math.floor(n);
}

function normalizeExecutor(value, fallback = 'aider') {
  const normalized = String(value ?? fallback).trim().toLowerCase();
  if (CODE_EXECUTORS.has(normalized)) return normalized;
  return fallback;
}

function csvSet(value) {
  return new Set(
    String(value ?? '')
      .split(',')
      .map((item) => item.trim().toLowerCase())
      .filter(Boolean),
  );
}

function appendLimited(current, chunk, limit) {
  const next = `${current}${Buffer.isBuffer(chunk) ? chunk.toString('utf8') : String(chunk ?? '')}`;
  if (next.length <= limit) return next;
  return next.slice(next.length - limit);
}

export function extractToolInstruction(userMessage) {
  const content = userMessage?.content;
  if (typeof content === 'string') return content.trim();
  if (!Array.isArray(content)) {
    return String(userMessage?.text ?? userMessage?.value ?? '').trim();
  }
  return content
    .map((item) => {
      if (typeof item === 'string') return item;
      if (item?.type === 'text') return item.text ?? '';
      return '';
    })
    .map((item) => String(item ?? '').trim())
    .filter(Boolean)
    .join('\n')
    .trim();
}

function runValidation(userMessage) {
  const metadata = userMessage?.metadata ?? {};
  const runMetadata = metadata.memindRun ?? metadata.agentRun ?? {};
  const validation = runMetadata.validation ?? metadata.toolGatewayValidation;
  return validation && typeof validation === 'object' && !Array.isArray(validation)
    ? validation
    : null;
}

function validationFilePaths(userMessage) {
  const validation = runValidation(userMessage);
  if (!validation) return [];
  const candidates = [
    validation.expectedFile ?? validation.expectedPath,
    ...(Array.isArray(validation.expectedFiles) ? validation.expectedFiles : []),
  ];
  return candidates
    .map((item) => {
      if (typeof item === 'string') return item.trim();
      if (!item || typeof item !== 'object' || Array.isArray(item)) return '';
      return String(item.path ?? item.file ?? item.relativePath ?? '').trim();
    })
    .filter(Boolean);
}

export function resolveAiderReceiptPath(userMessage, requestId) {
  const expected = `.memind/agent-runs/${String(requestId ?? '').trim()}.json`;
  return validationFilePaths(userMessage).find((item) => item === expected) ?? null;
}

export async function prepareAiderReceiptFile(cwd, relativePath) {
  if (!cwd || !relativePath) return null;
  const root = path.resolve(String(cwd));
  const target = path.resolve(root, relativePath);
  if (target !== root && !target.startsWith(`${root}${path.sep}`)) {
    throw new Error(`Aider receipt path escapes working directory: ${relativePath}`);
  }
  await fs.mkdir(path.dirname(target), { recursive: true });
  try {
    await fs.access(target);
  } catch {
    await fs.writeFile(
      target,
      `${JSON.stringify({ status: 'pending', executor: 'aider' }, null, 2)}\n`,
      { flag: 'wx' },
    );
  }
  return target;
}

async function resolveAiderContextFiles(userMessage, cwd) {
  const metadata = userMessage?.metadata ?? {};
  const runMetadata = metadata.memindRun ?? metadata.agentRun ?? {};
  const candidates = Array.isArray(runMetadata.aiderContextFiles)
    ? runMetadata.aiderContextFiles
    : [];
  if (!cwd || candidates.length === 0) return [];
  const root = path.resolve(String(cwd));
  const resolved = [];
  for (const relativePath of candidates.slice(0, 40)) {
    const target = path.resolve(root, String(relativePath ?? ''));
    if (target === root || !target.startsWith(`${root}${path.sep}`)) continue;
    try {
      const stat = await fs.stat(target);
      if (stat.isFile()) resolved.push(target);
    } catch {
      // Review context is best-effort; delivery validation remains authoritative.
    }
  }
  return resolved;
}

export function hardenAiderLaunchPlan(plan, receiptPath = null, contextFiles = []) {
  const args = [...(plan?.args ?? [])];
  for (const flag of ['--no-git', '--no-auto-commits', '--no-dirty-commits']) {
    if (!args.includes(flag)) args.push(flag);
  }
  for (const contextFile of contextFiles) {
    if (!args.includes(contextFile)) args.push('--file', contextFile);
  }
  if (receiptPath && !args.includes(receiptPath)) {
    args.push('--file', receiptPath);
  }
  return { ...plan, args };
}

export function createToolGateway({
  llmProviderService,
  env = process.env,
  spawnImpl = nodeSpawn,
} = {}) {
  const enabled = envFlag(env.MEMIND_TOOL_GATEWAY_ENABLED, false);
  const dryRun = envFlag(env.MEMIND_TOOL_GATEWAY_DRY_RUN, false);
  const defaultExecutor = normalizeExecutor(env.MEMIND_TOOL_GATEWAY_DEFAULT_EXECUTOR, 'aider');
  const openhandsTaskTypes = csvSet(
    env.MEMIND_TOOL_GATEWAY_OPENHANDS_TASK_TYPES
      ?? 'repo_refactor,multi_file,complex_repo,page_data_dev_complex',
  );
  const stdioLimit = positiveInteger(env.MEMIND_TOOL_GATEWAY_STDIO_LIMIT, DEFAULT_STDIO_LIMIT);

  function getStatus() {
    return {
      enabled,
      dryRun,
      protocol: 'agent-run-v1',
      executors: ['aider', 'openhands'],
      defaultExecutor,
      openhandsTaskTypes: [...openhandsTaskTypes],
    };
  }

  function selectExecutor({ userMessage, taskType } = {}) {
    const metadata = userMessage?.metadata ?? {};
    const runMetadata = metadata.memindRun ?? metadata.agentRun ?? {};
    const requested = normalizeExecutor(runMetadata.executor, '');
    if (requested) return requested;
    const normalizedTaskType = String(taskType ?? runMetadata.taskType ?? '').trim().toLowerCase();
    if (openhandsTaskTypes.has(normalizedTaskType)) return 'openhands';
    return defaultExecutor;
  }

  async function executeJob({
    runId,
    requestId,
    userId,
    userMessage,
    taskType,
    cwd,
    timeoutMs = 15 * 60 * 1000,
  } = {}) {
    if (!enabled) {
      throw new Error('Tool Gateway is disabled');
    }
    if (!llmProviderService?.getExecutorLaunchPlan) {
      throw new Error('Tool Gateway missing llm provider service');
    }
    const instruction = extractToolInstruction(userMessage);
    if (!instruction) {
      throw new Error('Tool Gateway job missing instruction');
    }
    const executor = selectExecutor({ userMessage, taskType });
    const receiptPath = executor === 'aider'
      ? resolveAiderReceiptPath(userMessage, requestId)
      : null;
    const executorInstruction = receiptPath
      ? `${instruction}\n\nThe validation receipt is already included in the Aider chat. Edit it directly; do not ask the user to add it.`
      : instruction;
    let plan = await llmProviderService.getExecutorLaunchPlan(executor, {
      cwd,
      mode: 'headless',
      instruction: executorInstruction,
      purpose: 'default',
      includeSecret: true,
    });
    if (!plan?.ok) {
      throw new Error(plan?.message ?? `Tool Gateway launch plan unavailable for ${executor}`);
    }
    if (executor === 'aider') {
      const preparedReceipt = dryRun
        ? (receiptPath ? path.resolve(String(cwd), receiptPath) : null)
        : await prepareAiderReceiptFile(cwd, receiptPath);
      const contextFiles = await resolveAiderContextFiles(userMessage, cwd);
      plan = hardenAiderLaunchPlan(plan, preparedReceipt, contextFiles);
    }
    if (dryRun) {
      return {
        ok: true,
        dryRun: true,
        executor,
        protocol: 'agent-run-v1',
        cwd: plan.cwd,
        command: plan.command,
        args: plan.args ?? [],
        runId,
        requestId,
        userId,
      };
    }

    return await new Promise((resolve, reject) => {
      let stdout = '';
      let stderr = '';
      const child = spawnImpl(plan.command, plan.args ?? [], {
        cwd: plan.cwd,
        env: { ...process.env, ...(plan.env ?? {}) },
        stdio: ['ignore', 'pipe', 'pipe'],
      });
      const cleanup = () => {
        if (timer) clearTimeout(timer);
      };
      const timer = setTimeout(() => {
        child.kill('SIGTERM');
        const err = new Error(`Tool Gateway job timed out after ${timeoutMs}ms`);
        err.code = 'TOOL_GATEWAY_TIMEOUT';
        reject(err);
      }, timeoutMs);

      if (child.stdout instanceof EventEmitter) {
        child.stdout.on('data', (chunk) => {
          stdout = appendLimited(stdout, chunk, stdioLimit);
        });
      }
      if (child.stderr instanceof EventEmitter) {
        child.stderr.on('data', (chunk) => {
          stderr = appendLimited(stderr, chunk, stdioLimit);
        });
      }
      child.on('error', (err) => {
        cleanup();
        reject(err);
      });
      child.on('exit', (code, signal) => {
        cleanup();
        if (code === 0) {
          resolve({
            ok: true,
            executor,
            protocol: 'agent-run-v1',
            cwd: plan.cwd,
            command: plan.command,
            args: plan.args ?? [],
            exitCode: code,
            signal: signal ?? null,
            stdout,
            stderr,
          });
          return;
        }
        const err = new Error(`Tool Gateway executor ${executor} exited with ${signal ?? code}`);
        err.code = 'TOOL_GATEWAY_EXECUTOR_FAILED';
        err.executor = executor;
        err.exitCode = code;
        err.signal = signal ?? null;
        err.stdout = stdout;
        err.stderr = stderr;
        reject(err);
      });
    });
  }

  return {
    getStatus,
    selectExecutor,
    executeJob,
  };
}