import { spawn } from "node:child_process";
import { createHash } from "node:crypto";
import { existsSync, mkdirSync, readFileSync, readdirSync, statSync, writeFileSync, unlinkSync } from "node:fs";
import { join, resolve } from "node:path";
import type { BacktestConfig, BacktestResult, LiveStrategyState, StrategyInfo } from "../shared/strategyTypes.js";

const QUANT_DIR = resolve(process.env.QUANT_PROJECT_DIR || join(process.cwd(), "../quant"));
const CACHE_DIR = join(process.env.STOCK_AGENT_DATA_DIR || join(process.cwd(), "data"), "strategy_cache");
const TIMEOUT_MS = Number(process.env.QUANT_BACKTEST_TIMEOUT_MS) || 180_000;
const CACHE_TTL_MS = 24 * 60 * 60 * 1000;
const MAX_CACHE_FILES = 50;

function ensureCacheDir(): void {
  if (!existsSync(CACHE_DIR)) {
    mkdirSync(CACHE_DIR, { recursive: true });
  }
}

function configHash(config: BacktestConfig): string {
  const serialized = stableStringify(config);
  return createHash("md5").update(serialized).digest("hex").slice(0, 12);
}

function stableStringify(value: unknown): string {
  if (Array.isArray(value)) {
    return `[${value.map((item) => stableStringify(item)).join(",")}]`;
  }
  if (value && typeof value === "object") {
    return `{${Object.keys(value)
      .sort()
      .map((key) => `${JSON.stringify(key)}:${stableStringify((value as Record<string, unknown>)[key])}`)
      .join(",")}}`;
  }
  return JSON.stringify(value);
}

function runBridge(args: string[]): Promise<unknown> {
  return new Promise((resolve, reject) => {
    const proc = spawn("uv", ["run", "python", "bridge.py", ...args], {
      cwd: QUANT_DIR,
      env: { ...process.env, PYTHONUNBUFFERED: "1" },
    });

    const chunks: Buffer[] = [];
    let stderr = "";
    let exitCode: number | null = null;
    let stdoutEnded = false;
    let exited = false;

    function tryFinish() {
      if (!stdoutEnded || !exited) return;
      clearTimeout(timer);
      const stdout = Buffer.concat(chunks).toString("utf-8");
      if (exitCode !== 0) {
        reject(new Error(`bridge.py exited with code ${exitCode}: ${stderr.slice(-1000)}`));
      } else {
        try {
          resolve(JSON.parse(stdout));
        } catch {
          reject(new Error(`Failed to parse bridge output (${stdout.length} bytes): ${stdout.slice(0, 200)}`));
        }
      }
    }

    proc.stdout.on("data", (chunk: Buffer) => { chunks.push(chunk); });
    proc.stderr.on("data", (chunk: Buffer) => { stderr += chunk.toString(); });
    proc.stdout.on("end", () => { stdoutEnded = true; tryFinish(); });
    proc.on("close", (code) => { exitCode = code; exited = true; tryFinish(); });

    const timer = setTimeout(() => {
      proc.kill("SIGTERM");
      reject(new Error(`Bridge timeout after ${TIMEOUT_MS}ms. stderr: ${stderr.slice(-500)}`));
    }, TIMEOUT_MS);

    proc.on("error", (err) => {
      clearTimeout(timer);
      reject(new Error(`Failed to spawn bridge.py: ${err.message}`));
    });
  });
}

function evictOldCache(): void {
  ensureCacheDir();
  const files = readdirSync(CACHE_DIR)
    .filter((f) => f.endsWith(".json"))
    .map((f) => ({ name: f, mtime: statSync(join(CACHE_DIR, f)).mtimeMs }))
    .sort((a, b) => b.mtime - a.mtime);

  while (files.length > MAX_CACHE_FILES) {
    const old = files.pop()!;
    unlinkSync(join(CACHE_DIR, old.name));
  }
}

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

let cachedStrategies: { data: StrategyInfo[]; fetchedAt: number } | null = null;

export async function listStrategies(): Promise<StrategyInfo[]> {
  if (cachedStrategies && Date.now() - cachedStrategies.fetchedAt < CACHE_TTL_MS) {
    return cachedStrategies.data;
  }
  const data = (await runBridge(["list"])) as StrategyInfo[];
  cachedStrategies = { data, fetchedAt: Date.now() };
  return data;
}

export async function runBacktest(config: BacktestConfig): Promise<BacktestResult> {
  const id = configHash(config);
  ensureCacheDir();

  // Check cache
  const cachePath = join(CACHE_DIR, `${id}.json`);
  if (existsSync(cachePath)) {
    const stat = statSync(cachePath);
    if (Date.now() - stat.mtimeMs < CACHE_TTL_MS) {
      return normalizeBacktestResult(JSON.parse(readFileSync(cachePath, "utf-8")) as BacktestResult);
    }
  }

  // Run backtest
  const args = [
    "backtest",
    "--strategies", config.strategies.join(","),
    "--market", config.market,
    "--years", String(config.years),
    "--capital", String(config.initialCapital),
    "--fixed-fee", String(config.fixedFee),
    "--tx-cost", String(config.txCost),
  ];

  if (config.injectionSchedule) {
    args.push("--injection", JSON.stringify(config.injectionSchedule));
  }

  const raw = await runBridge(args);

  const result = normalizeBacktestResult({
    id,
    ...(raw as Omit<BacktestResult, "id" | "computedAt">),
    computedAt: new Date().toISOString(),
  });

  // Cache result
  writeFileSync(cachePath, `${JSON.stringify(result)}\n`);
  evictOldCache();

  return result;
}

export async function getCachedResult(id: string): Promise<BacktestResult | null> {
  ensureCacheDir();
  const cachePath = join(CACHE_DIR, `${id}.json`);
  if (!existsSync(cachePath)) return null;
  return normalizeBacktestResult(JSON.parse(readFileSync(cachePath, "utf-8")) as BacktestResult);
}

export async function getLiveStrategies(market: string, strategy?: string): Promise<LiveStrategyState[]> {
  const args = ["live", "--market", market];
  if (strategy) args.push("--strategy", strategy);
  return (await runBridge(args)) as LiveStrategyState[];
}

function normalizeBacktestResult(result: BacktestResult): BacktestResult {
  return {
    ...result,
    strategies: result.strategies.map((strategy) => ({
      ...strategy,
      label: typeof strategy.label === "string" && strategy.label.trim() ? strategy.label : strategy.name
    })),
    benchmark: {
      name: result.benchmark?.name || "Benchmark",
      equityCurve: result.benchmark?.equityCurve ?? []
    }
  };
}