import { spawn } from "node:child_process";
import { createHash, randomUUID } from "node:crypto";
import {
  closeSync, constants as fsConstants, existsSync, fchmodSync, fstatSync, fsyncSync, lstatSync, mkdirSync,
  openSync, readFileSync, readSync, realpathSync, statSync, unlinkSync, writeFileSync,
} from "node:fs";
import { isAbsolute, join } from "node:path";
import { clearPrincipalEnvironment, principalEnvironment, type PrincipalContext } from "../auth/principal.js";
import { secretValue, type SecretBundleConfig } from "../config/secret-bundle.js";

export interface ThtConfig extends SecretBundleConfig {
  thtBin: string;
  harnessDir: string;
  configPath: string;
  dataRoot?: string;
  runtimeSnapshotRoot?: string;
}

export interface SessionRow {
  id: string;
  status: string;
  question: string;
  summary: string | null;
  created_at: string;
  updated_at: string | null;
  author: string | null;
}

export interface SessionDocument {
  phase: string;
  key: string;
  title: string;
  format: string;
  content: string;
}

export interface OllamaEnsureResult {
  ok: boolean;
  stage?: string;
  error?: string;
  server?: string;
  model?: string;
  model_name?: string;
}

interface RuntimeSnapshot {
  path: string;
  dev: number;
  ino: number;
  size: number;
  mode: number;
  digest: string;
}

export class ThtRunner {
  private readonly runtimeSnapshots = new Map<string, RuntimeSnapshot>();

  constructor(private cfg: ThtConfig, private principal?: PrincipalContext) {}

  /** Bind one trusted request principal to every child spawned by this runner. */
  withPrincipal(principal: PrincipalContext): ThtRunner { return new ThtRunner(this.cfg, principal); }

  /**
   * Resolve the `-c <config>` args. A named workspace MUST exist: silently falling
   * back to the default config would point every operation at the wrong workspace
   * (wrong DB, wrong sessions dir) — fail loud instead.
   */
  private configArg(workspaceConfigPath?: string): string[] {
    if (workspaceConfigPath) {
      if (isAbsolute(workspaceConfigPath)) {
        this.assertTrustedRuntimeSnapshot(workspaceConfigPath);
        return ["-c", workspaceConfigPath];
      }
      if (workspaceConfigPath.includes("/")) {
        throw new Error("workspace snapshot config path must be absolute");
      }
      const workspace = workspaceConfigPath;
      if (!existsSync(join(this.cfg.harnessDir, "workspaces", `${workspace}.yaml`))) {
        throw new Error(`workspace non trovato: workspaces/${workspace}.yaml (harness: ${this.cfg.harnessDir})`);
      }
      return ["-c", `workspaces/${workspace}.yaml`];
    }
    return ["-c", this.cfg.configPath];
  }

  private runtimeSnapshotDirectory(): string {
    if (!this.cfg.runtimeSnapshotRoot) throw new Error("runtime snapshot root is not configured");
    if (!isAbsolute(this.cfg.runtimeSnapshotRoot)) throw new Error("runtime snapshot root must be absolute");
    mkdirSync(this.cfg.runtimeSnapshotRoot, { recursive: true, mode: 0o700 });
    const directory = lstatSync(this.cfg.runtimeSnapshotRoot);
    if (!directory.isDirectory() || directory.isSymbolicLink() || (directory.mode & 0o077) !== 0) {
      throw new Error("runtime snapshot root is not trusted");
    }
    return realpathSync(this.cfg.runtimeSnapshotRoot);
  }

  private static isRestrictiveMode(mode: number): boolean {
    const permissions = mode & 0o777;
    return (permissions & 0o400) !== 0 && (permissions & ~0o600) === 0;
  }

  private assertTrustedRuntimeSnapshot(path: string): RuntimeSnapshot {
    const snapshot = this.runtimeSnapshots.get(path);
    if (!snapshot) throw new Error("config path is not a trusted runtime snapshot");
    try {
      const entry = lstatSync(path);
      const stat = statSync(path);
      if (
        !entry.isFile() || entry.isSymbolicLink()
        || stat.dev !== snapshot.dev || stat.ino !== snapshot.ino || stat.size !== snapshot.size
        || (stat.mode & 0o777) !== snapshot.mode || !ThtRunner.isRestrictiveMode(stat.mode)
        || createHash("sha256").update(readFileSync(path)).digest("hex") !== snapshot.digest
      ) throw new Error("changed runtime snapshot");
      return snapshot;
    } catch {
      throw new Error("config path is not a trusted runtime snapshot");
    }
  }

  /** Create an opaque, backend-owned temporary config that is safe to hand to `tht`. */
  createRuntimeSnapshot(config: string): string {
    const directory = this.runtimeSnapshotDirectory();
    const path = join(directory, `runtime-${randomUUID()}.yaml`);
    const fd = openSync(
      path,
      fsConstants.O_WRONLY | fsConstants.O_CREAT | fsConstants.O_EXCL | fsConstants.O_NOFOLLOW,
      0o600,
    );
    try {
      writeFileSync(fd, config, "utf8");
      fsyncSync(fd);
      fchmodSync(fd, 0o400);
      const stat = fstatSync(fd);
      this.runtimeSnapshots.set(path, {
        path,
        dev: stat.dev,
        ino: stat.ino,
        size: stat.size,
        mode: stat.mode & 0o777,
        digest: createHash("sha256").update(config, "utf8").digest("hex"),
      });
      return path;
    } catch (error) {
      try { unlinkSync(path); } catch { /* creation did not produce a removable file */ }
      throw error;
    } finally {
      closeSync(fd);
    }
  }

  cleanupRuntimeSnapshot(path: string): void {
    const snapshot = this.runtimeSnapshots.get(path);
    if (!snapshot) return;
    this.runtimeSnapshots.delete(path);
    try { unlinkSync(snapshot.path); } catch { /* a changed path is never removed recursively */ }
  }

  private openTrustedRuntimeSnapshot(path: string): number {
    const snapshot = this.assertTrustedRuntimeSnapshot(path);
    const fd = openSync(path, fsConstants.O_RDONLY | fsConstants.O_NOFOLLOW);
    try {
      const stat = fstatSync(fd);
      if (
        !stat.isFile() || stat.dev !== snapshot.dev || stat.ino !== snapshot.ino || stat.size !== snapshot.size
        || (stat.mode & 0o777) !== snapshot.mode || !ThtRunner.isRestrictiveMode(stat.mode)
      ) throw new Error("changed runtime snapshot");
      const contents = Buffer.alloc(snapshot.size);
      let offset = 0;
      while (offset < contents.length) {
        const bytes = readSync(fd, contents, offset, contents.length - offset, offset);
        if (bytes === 0) throw new Error("truncated runtime snapshot");
        offset += bytes;
      }
      if (createHash("sha256").update(contents).digest("hex") !== snapshot.digest) {
        throw new Error("changed runtime snapshot");
      }
      return fd;
    } catch {
      closeSync(fd);
      throw new Error("config path is not a trusted runtime snapshot");
    }
  }

  async runWithRuntimeSnapshot(
    args: string[], config: string, timeoutMs: number = ThtRunner.DEFAULT_TIMEOUT_MS,
  ): Promise<{ code: number; stdout: string; stderr: string }> {
    const snapshot = this.createRuntimeSnapshot(config);
    try {
      return await this.run(args, snapshot, timeoutMs);
    } finally {
      this.cleanupRuntimeSnapshot(snapshot);
    }
  }

  /**
   * Build the full argv for a `tht` invocation. `--config`/`-c` is a PER-COMMAND
   * option in the `tht` CLI (there is NO global `-c`), so it MUST be appended
   * AFTER the subcommand + its flags, never prepended.
   */
  buildArgv(args: string[], workspace?: string): string[] {
    return [...args, ...this.configArg(workspace)];
  }

  // Every route awaits these children; without a ceiling, one hung DWH/vector call
  // (dropped VPN mid-connect) wedges its HTTP request forever. Session/file commands
  // get the default; DWH-touching commands pass a wider explicit budget.
  static readonly DEFAULT_TIMEOUT_MS = 60_000;
  static readonly DWH_TIMEOUT_MS = 120_000;

  run(
    args: string[], workspaceConfigPath?: string, timeoutMs: number = ThtRunner.DEFAULT_TIMEOUT_MS,
  ): Promise<{ code: number; stdout: string; stderr: string }> {
    return new Promise((resolve) => {
      const env: NodeJS.ProcessEnv = { ...process.env };
      delete env.THT_DATA_ROOT;
      clearPrincipalEnvironment(env);
      if (this.cfg.dataRoot !== undefined) env.THT_DATA_ROOT = this.cfg.dataRoot;
      if (this.principal) Object.assign(env, principalEnvironment(this.principal));
      for (const name of [
        "THT_DWH_API_KEY", "THT_VEC_API_KEY", "THT_VEC_WRITE_API_KEY",
      ] as const) {
        const value = secretValue(this.cfg, name);
        if (value !== undefined) env[name] = value;
      }
      const ca = secretValue(this.cfg, "THT_SSL_CA") ?? secretValue(this.cfg, "THT_CA");
      if (ca !== undefined) {
        env.THT_CA = ca;
        env.THT_SSL_CA = ca;
      }
      let snapshotFd: number | undefined;
      let ch;
      try {
        snapshotFd = workspaceConfigPath && isAbsolute(workspaceConfigPath)
          ? this.openTrustedRuntimeSnapshot(workspaceConfigPath)
          : undefined;
        ch = spawn(
          this.cfg.thtBin,
          snapshotFd === undefined
            ? this.buildArgv(args, workspaceConfigPath)
            : [...args, "-c", "/dev/fd/3"],
          {
            cwd: this.cfg.harnessDir,
            env,
            ...(snapshotFd === undefined ? {} : { stdio: ["ignore", "pipe", "pipe", snapshotFd] }),
          },
        );
      } finally {
        if (snapshotFd !== undefined) closeSync(snapshotFd);
      }
      let stdout = "";
      let stderr = "";
      let settled = false;
      let timer: ReturnType<typeof setTimeout> | undefined;
      const finish = (result: { code: number; stdout: string; stderr: string }) => {
        if (settled) return;
        settled = true;
        if (timer) clearTimeout(timer);
        resolve(result);
      };
      if (timeoutMs !== undefined) {
        timer = setTimeout(() => {
          try { ch.kill("SIGKILL"); } catch { /* already gone */ }
          finish({ code: 124, stdout, stderr: stderr || `timed out after ${timeoutMs}ms` });
        }, timeoutMs);
      }
      ch.stdout?.on("data", (d: Buffer) => (stdout += d));
      ch.stderr?.on("data", (d: Buffer) => (stderr += d));
      ch.on("error", (error) => finish({ code: 1, stdout, stderr: stderr || error.message }));
      ch.on("close", (code) => finish({ code: code ?? 0, stdout, stderr }));
    });
  }

  private async json<T>(args: string[], workspace?: string, timeoutMs?: number): Promise<T> {
    const { code, stdout, stderr } = await this.run(args, workspace, timeoutMs);
    if (code !== 0) throw new Error(`tht ${args.join(" ")} exit ${code}: ${stderr.trim()}`);
    return JSON.parse(stdout) as T;
  }

  private async ok(args: string[], workspace?: string): Promise<void> {
    const { code, stderr } = await this.run(args, workspace);
    if (code !== 0) throw new Error(`tht ${args.join(" ")} exit ${code}: ${stderr.trim()}`);
  }

  async sessionNew(o: {
    question: string;
    provider?: string;
    model?: string;
    thinking?: string;
    name?: string;
    workspace?: string;
  }) {
    const a = ["session", "new", o.question];
    for (const [f, v] of [
      ["--provider", o.provider],
      ["--model", o.model],
      ["--thinking", o.thinking],
      ["--name", o.name],
    ] as const) {
      if (v) a.push(f, v);
    }
    a.push("--json");
    return this.json<{ id: string }>(a, o.workspace);
  }

  /** Build and persist the deterministic F1 retrieval pack for a new session. */
  async searchPack(question: string, sessionId: string, workspace?: string): Promise<void> {
    const args = ["search", "pack", question, "--session", sessionId];
    const { code, stderr } = await this.run(args, workspace, ThtRunner.DWH_TIMEOUT_MS);
    if (code !== 0) throw new Error(`tht ${args.join(" ")} exit ${code}: ${stderr.trim()}`);
  }

  /**
   * Probe DWH reachability via `tht db ping` (a REST health check). Never throws —
   * returns ok=false with the failure detail so the caller can refuse a new session
   * cleanly. Timed out to keep POST /sessions responsive when the host hangs.
   */
  async dbPing(workspace?: string): Promise<{ ok: boolean; detail: string }> {
    const { code, stdout, stderr } = await this.run(["db", "ping"], workspace, 5_000);
    if (code === 0) return { ok: true, detail: stdout.trim() };
    return { ok: false, detail: (stderr || stdout).trim() };
  }

  sessionList(workspace?: string) {
    return this.json<SessionRow[]>(["session", "list", "--json"], workspace);
  }

  sessionShow(id: string, workspace?: string) {
    return this.json<unknown>(["session", "show", id, "--json"], workspace);
  }

  sqlPreview(id: string, p: { limit?: number; offset?: number }, workspace?: string) {
    // No positional FILE: the harness resolves sql_final.sql from the session
    // via _session_sql_file(cfg, session_id), which respects the workspace path.
    const a = ["sql", "preview", "--session", id, "--json"];
    if (p.limit != null) a.push("--limit", String(p.limit));
    if (p.offset != null) a.push("--offset", String(p.offset));
    return this.json<{
      columns: string[];
      rows: unknown[][];
      execution_ms: number;
      truncated: boolean;
    }>(a, workspace, ThtRunner.DWH_TIMEOUT_MS);
  }

  async sqlExport(id: string, workspace?: string) {
    const { code, stdout, stderr } = await this.run(
      ["sql", "export", "--session", id], workspace, ThtRunner.DWH_TIMEOUT_MS,
    );
    if (code !== 0) throw new Error(`tht sql export exit ${code}: ${stderr.trim()}`);
    return { path: stdout.trim() };
  }

  closeSession(id: string, workspace?: string) { return this.ok(["session", "close", id], workspace); }
  failSession(id: string, workspace?: string) { return this.ok(["session", "fail", id], workspace); }
  reopenSession(id: string, workspace?: string) { return this.ok(["session", "reopen", id], workspace); }
  setName(id: string, name: string, workspace?: string) { return this.ok(["session", "set-name", id, "--name", name], workspace); }
  setGroup(id: string, group: string, workspace?: string) { return this.ok(["session", "set-group", id, "--group", group], workspace); }
  archive(id: string, workspace?: string) { return this.ok(["session", "archive", id], workspace); }
  unarchive(id: string, workspace?: string) { return this.ok(["session", "unarchive", id], workspace); }
  async deleteSession(id: string, workspace?: string) {
    const { code, stderr } = await this.run(["session", "delete", id], workspace);
    if (code !== 0) throw new Error(`tht session delete exit ${code}: ${stderr.trim()}`);
  }
  documents(id: string, workspace?: string) { return this.json<SessionDocument[]>(["session", "documents", id, "--json"], workspace); }

  preferencesGet(workspace?: string) { return this.json<Record<string, unknown>>(["session", "preferences", "get", "--json"], workspace); }
  async preferencesSet(preferences: Record<string, unknown>, workspace?: string): Promise<void> {
    await this.ok(["session", "preferences", "set", "--json", JSON.stringify(preferences)], workspace);
  }

  async ollamaEnsure(workspace: string, timeoutSec: number): Promise<OllamaEnsureResult> {
    // Process budget wider than the CLI's own --timeout so the CLI reports its
    // failure itself; SIGKILL is only the backstop for a wedged child.
    const { code, stdout, stderr } = await this.run(
      ["ollama", "ensure", "--json", "--timeout", String(timeoutSec)],
      workspace,
      timeoutSec * 1000 + 30_000,
    );
    let parsed: Partial<OllamaEnsureResult> | null = null;
    try { parsed = JSON.parse(stdout.trim()); } catch { /* not JSON */ }
    // Exit 0 with unparseable output is NOT a verified readiness: --json promises
    // pristine JSON, so treat the violation as a failed check, never as ok.
    if (code === 0 && parsed !== null) return { ok: true, ...parsed };
    if (code === 0) {
      return { ok: false, error: `tht ollama ensure: output non-JSON: ${stdout.trim().slice(0, 200)}` };
    }
    return {
      ok: false,
      stage: parsed?.stage,
      error: parsed?.error ?? (stderr.trim() || `tht ollama ensure exit ${code}`),
    };
  }
}