import { execFile } from "node:child_process";
import { constants } from "node:fs";
import { access, readFile } from "node:fs/promises";
import { resolve } from "node:path";
import { promisify } from "node:util";
import { Pool } from "pg";

import { type Config, loadConfigFromSources } from "../../../packages/core/src/config.js";

const execFileAsync = promisify(execFile);

export type DoctorStatus = "pass" | "fail" | "warn";

export interface DoctorResult {
  name: string;
  status: DoctorStatus;
  detail: string;
  remediation: string;
}

export interface CommandResult {
  exitCode: number;
  stdout: string;
  stderr: string;
}

export type DoctorCommandRunner = (
  command: string,
  args?: string[],
  options?: { cwd?: string; env?: NodeJS.ProcessEnv },
) => Promise<CommandResult>;

export interface DoctorOptions {
  cwd?: string;
  env?: Record<string, string | undefined>;
  nodeVersion?: string;
  commandRunner?: DoctorCommandRunner;
  connectDatabase?: (databaseUrl: string) => Promise<void>;
  countAppliedMigrations?: (databaseUrl: string) => Promise<number>;
  countExpectedMigrations?: (cwd: string) => Promise<number> | number;
  dockerComposePath?: string;
}

const MIN_DISK_KB = 5 * 1024 * 1024;
const WARN_DISK_KB = 10 * 1024 * 1024;
const FAIL_DISK_KB = 2 * 1024 * 1024;

export async function runDoctor(options: DoctorOptions = {}): Promise<DoctorResult[]> {
  const cwd = options.cwd ?? process.cwd();
  const env = options.env ?? process.env;
  const commandRunner = options.commandRunner ?? defaultCommandRunner;
  const dockerCommand = options.dockerComposePath ?? "docker";
  const results: DoctorResult[] = [];
  const configResult = loadDoctorConfig(cwd, env);

  results.push(checkNodeVersion(options.nodeVersion ?? process.versions.node));
  results.push(await checkCommandVersion("pnpm", ["--version"], "9.0.0", commandRunner));
  results.push(await checkCommandVersion("tmux", ["-V"], "3.3.0", commandRunner));
  results.push(await checkCommandVersion("git", ["--version"], "2.40.0", commandRunner));
  results.push(await checkDocker(commandRunner));
  results.push(
    await checkPostgres({
      commandRunner,
      config: configResult.config,
      configError: configResult.error,
      connectDatabase: options.connectDatabase ?? defaultConnectDatabase,
      dockerCommand,
      cwd,
    }),
  );
  results.push(
    await checkMigrations({
      config: configResult.config,
      configError: configResult.error,
      countAppliedMigrations: options.countAppliedMigrations ?? defaultCountAppliedMigrations,
      countExpectedMigrations: options.countExpectedMigrations ?? defaultCountExpectedMigrations,
      cwd,
    }),
  );
  results.push(await checkWorkspaceRoot(configResult.config, configResult.error));
  results.push(checkConfig(configResult.config, configResult.error));
  results.push(await checkOptionalBinary("codex", commandRunner));
  results.push(await checkOptionalBinary("claude", commandRunner));
  results.push(await checkWorkspaceDisk(configResult.config, commandRunner));

  return results;
}

function loadDoctorConfig(
  cwd: string,
  env: Record<string, string | undefined>,
): { config?: Config; error?: unknown } {
  try {
    return { config: loadConfigFromSources({ cwd, env }) };
  } catch (error) {
    return { error };
  }
}

function checkNodeVersion(version: string): DoctorResult {
  if (satisfiesMin(version, "22.0.0") && compareVersions(version, "23.0.0") < 0) {
    return pass("node", version, "Node is within >=22.0.0 <23");
  }

  return fail("node", version, "Install Node 22 LTS and rerun doctor");
}

async function checkCommandVersion(
  name: string,
  args: string[],
  minimum: string,
  commandRunner: DoctorCommandRunner,
): Promise<DoctorResult> {
  const result = await safeRun(commandRunner, name, args);

  if (!result.ok) {
    return fail(name, result.error, `Install ${name} >= ${minimum}`);
  }

  if (result.value.exitCode !== 0) {
    return fail(
      name,
      (result.value.stderr || result.value.stdout).trim(),
      `Install ${name} >= ${minimum}`,
    );
  }

  const version = extractVersion(result.value.stdout);
  if (!version) {
    return fail(name, result.value.stdout.trim(), `Ensure ${name} reports a version`);
  }

  return satisfiesMin(version, minimum)
    ? pass(name, version, `${name} satisfies >= ${minimum}`)
    : fail(name, version, `Upgrade ${name} to >= ${minimum}`);
}

async function checkDocker(commandRunner: DoctorCommandRunner): Promise<DoctorResult> {
  const result = await safeRun(commandRunner, "docker", ["info", "--format", "{{.ServerVersion}}"]);

  if (!result.ok) {
    return fail("docker", result.error, "Start Docker and ensure docker is in PATH");
  }

  return result.value.exitCode === 0
    ? pass("docker", result.value.stdout.trim(), "Docker daemon is reachable")
    : fail("docker", result.value.stderr.trim(), "Start Docker and rerun doctor");
}

async function checkPostgres(input: {
  commandRunner: DoctorCommandRunner;
  config: Config | undefined;
  configError: unknown;
  connectDatabase: (databaseUrl: string) => Promise<void>;
  dockerCommand: string;
  cwd: string;
}): Promise<DoctorResult> {
  if (!input.config) {
    return fail("postgres", errorDetail(input.configError), "Fix Config before checking Postgres");
  }

  const compose = await safeRun(
    input.commandRunner,
    input.dockerCommand,
    ["compose", "ps", "postgres"],
    {
      cwd: input.cwd,
    },
  );

  if (!compose.ok || compose.value.exitCode !== 0 || !compose.value.stdout.includes("postgres")) {
    return fail(
      "postgres",
      compose.ok ? compose.value.stderr : compose.error,
      "Run docker compose up -d postgres",
    );
  }

  const ready = await safeRun(input.commandRunner, input.dockerCommand, [
    "compose",
    "exec",
    "-T",
    "postgres",
    "pg_isready",
    "-U",
    "devflow",
    "-d",
    "devflow",
  ]);

  if (!ready.ok || ready.value.exitCode !== 0) {
    return fail(
      "postgres",
      ready.ok ? ready.value.stderr : ready.error,
      "Wait for Postgres healthcheck to pass",
    );
  }

  try {
    await input.connectDatabase(input.config.DATABASE_URL);
    return pass("postgres", "connected", "Postgres is reachable and accepts DATABASE_URL");
  } catch (error) {
    return fail("postgres", errorDetail(error), "Check DATABASE_URL and container health");
  }
}

async function checkMigrations(input: {
  config: Config | undefined;
  configError: unknown;
  countAppliedMigrations: (databaseUrl: string) => Promise<number>;
  countExpectedMigrations: (cwd: string) => Promise<number> | number;
  cwd: string;
}): Promise<DoctorResult> {
  if (!input.config) {
    return fail(
      "drizzle_migrations",
      errorDetail(input.configError),
      "Fix Config before checking migrations",
    );
  }

  try {
    const [applied, expected] = await Promise.all([
      input.countAppliedMigrations(input.config.DATABASE_URL),
      input.countExpectedMigrations(input.cwd),
    ]);

    if (applied >= expected) {
      return pass("drizzle_migrations", `${applied}/${expected}`, "No pending migrations");
    }

    return fail("drizzle_migrations", `${applied}/${expected}`, "Run pnpm db:migrate");
  } catch (error) {
    return fail(
      "drizzle_migrations",
      errorDetail(error),
      "Run pnpm db:migrate after Postgres is healthy",
    );
  }
}

async function checkWorkspaceRoot(config?: Config, configError?: unknown): Promise<DoctorResult> {
  if (!config) {
    return fail(
      "workspace_root",
      errorDetail(configError),
      "Set WORKSPACE_ROOT to an existing writable path",
    );
  }

  try {
    await access(config.WORKSPACE_ROOT, constants.W_OK);
    return pass("workspace_root", config.WORKSPACE_ROOT, "Workspace root is writable");
  } catch (error) {
    return fail("workspace_root", errorDetail(error), "Create WORKSPACE_ROOT and make it writable");
  }
}

function checkConfig(config?: Config, configError?: unknown): DoctorResult {
  return config
    ? pass("config", "valid", ".env resolved to a valid Config")
    : fail("config", errorDetail(configError), "Set DATABASE_URL, WORKSPACE_ROOT, and LOG_LEVEL");
}

async function checkOptionalBinary(
  name: "codex" | "claude",
  commandRunner: DoctorCommandRunner,
): Promise<DoctorResult> {
  const result = await safeRun(commandRunner, name, ["--version"]);

  return result.ok && result.value.exitCode === 0
    ? pass(name, result.value.stdout.trim(), `${name} backend can be enabled`)
    : warn(name, "not found", `${name} is only required for real backend opt-in`);
}

async function checkWorkspaceDisk(
  config: Config | undefined,
  commandRunner: DoctorCommandRunner,
): Promise<DoctorResult> {
  if (!config) {
    return warn("workspace_disk", "unknown", "Fix Config before checking free disk");
  }

  const result = await safeRun(commandRunner, "df", ["-Pk", config.WORKSPACE_ROOT]);
  if (!result.ok || result.value.exitCode !== 0) {
    return warn(
      "workspace_disk",
      result.ok ? result.value.stderr : result.error,
      "Ensure df is available",
    );
  }

  const availableKb = Number.parseInt(result.value.stdout.trim().split(/\s+/).at(-3) ?? "", 10);
  if (Number.isNaN(availableKb)) {
    return warn("workspace_disk", result.value.stdout.trim(), "Unable to parse df output");
  }

  if (availableKb < FAIL_DISK_KB) {
    return fail(
      "workspace_disk",
      `${availableKb} KB free`,
      "Free at least 5GB under WORKSPACE_ROOT",
    );
  }

  if (availableKb < WARN_DISK_KB || availableKb < MIN_DISK_KB) {
    return warn(
      "workspace_disk",
      `${availableKb} KB free`,
      "Free space is below the recommended 10GB",
    );
  }

  return pass(
    "workspace_disk",
    `${availableKb} KB free`,
    "Workspace partition has enough free space",
  );
}

export function doctorExitCode(results: DoctorResult[]): 0 | 1 {
  return results.some((result) => result.status === "fail") ? 1 : 0;
}

export function formatDoctorJson(results: DoctorResult[]): string {
  return `${JSON.stringify(results, null, 2)}\n`;
}

export function formatDoctorTable(results: DoctorResult[]): string {
  const nameWidth = Math.max(...results.map((result) => result.name.length), "check".length);
  const statusWidth = "status".length;
  const lines = [
    `${"check".padEnd(nameWidth)}  ${"status".padEnd(statusWidth)}  detail`,
    `${"-".repeat(nameWidth)}  ${"-".repeat(statusWidth)}  ${"-".repeat(6)}`,
    ...results.map(
      (result) =>
        `${result.name.padEnd(nameWidth)}  ${result.status.padEnd(statusWidth)}  ${result.detail}${
          result.remediation ? ` (${result.remediation})` : ""
        }`,
    ),
  ];

  return `${lines.join("\n")}\n`;
}

async function defaultCommandRunner(
  command: string,
  args: string[] = [],
  options: { cwd?: string; env?: NodeJS.ProcessEnv } = {},
): Promise<CommandResult> {
  try {
    const result = await execFileAsync(command, args, {
      cwd: options.cwd,
      env: options.env,
      timeout: 15_000,
    });

    return {
      exitCode: 0,
      stdout: result.stdout,
      stderr: result.stderr,
    };
  } catch (error) {
    const maybeError = error as {
      code?: string | number;
      stdout?: string;
      stderr?: string;
      message?: string;
    };
    return {
      exitCode: typeof maybeError.code === "number" ? maybeError.code : 1,
      stdout: maybeError.stdout ?? "",
      stderr: maybeError.stderr || maybeError.message || String(error),
    };
  }
}

async function defaultConnectDatabase(databaseUrl: string): Promise<void> {
  const pool = new Pool({ connectionString: databaseUrl });
  try {
    await pool.query("select 1");
  } finally {
    await pool.end();
  }
}

async function defaultCountAppliedMigrations(databaseUrl: string): Promise<number> {
  const pool = new Pool({ connectionString: databaseUrl });
  try {
    const result = await pool.query<{ count: string }>(
      "select count(*)::text as count from drizzle.__drizzle_migrations",
    );

    return Number.parseInt(result.rows[0]?.count ?? "0", 10);
  } catch {
    return 0;
  } finally {
    await pool.end();
  }
}

async function defaultCountExpectedMigrations(cwd: string): Promise<number> {
  const journalPath = resolve(cwd, "packages/db/src/migrations/meta/_journal.json");
  const journal = JSON.parse(await readFile(journalPath, "utf8")) as { entries?: unknown[] };

  return journal.entries?.length ?? 0;
}

async function safeRun(
  commandRunner: DoctorCommandRunner,
  command: string,
  args: string[] = [],
  options?: { cwd?: string; env?: NodeJS.ProcessEnv },
): Promise<{ ok: true; value: CommandResult } | { ok: false; error: string }> {
  try {
    return { ok: true, value: await commandRunner(command, args, options) };
  } catch (error) {
    return { ok: false, error: errorDetail(error) };
  }
}

function extractVersion(output: string): string | undefined {
  return output.match(/\d+\.\d+\.\d+/)?.[0] ?? output.match(/\d+\.\d+/)?.[0];
}

function satisfiesMin(version: string, minimum: string): boolean {
  return compareVersions(version, minimum) >= 0;
}

function compareVersions(left: string, right: string): number {
  const leftParts = left.split(".").map((part) => Number.parseInt(part, 10));
  const rightParts = right.split(".").map((part) => Number.parseInt(part, 10));

  for (let index = 0; index < 3; index += 1) {
    const diff = (leftParts[index] ?? 0) - (rightParts[index] ?? 0);
    if (diff !== 0) {
      return diff;
    }
  }

  return 0;
}

function pass(name: string, detail: string, remediation: string): DoctorResult {
  return { name, status: "pass", detail, remediation };
}

function fail(name: string, detail: string, remediation: string): DoctorResult {
  return { name, status: "fail", detail, remediation };
}

function warn(name: string, detail: string, remediation: string): DoctorResult {
  return { name, status: "warn", detail, remediation };
}

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