import { SERVICE_NAME } from '../src/platform-identity.js';
import { execFileSync } from 'child_process';
import fs from 'fs';
import path from 'path';

import {
  ZFS_PREFIX,
} from '../src/config.js';
import type { FirstBootInstallMode } from './first-boot.js';
import { resolvePlatformRootDataset } from './install-identity.js';
import { commandExists } from './platform.js';
import { loadSystemEnv } from './system-env.js';
import { getZfsMetadata } from './zfs-metadata.js';

export interface ExistingInstallSignals {
  envFile: boolean;
  groupsDir: boolean;
  serviceFile: boolean;
  zfsDataset: boolean;
  zfsMetadata: boolean;
  runtimeUser: boolean;
}

export interface ExistingInstallDetection {
  signals: ExistingInstallSignals;
  strongSignals: string[];
  softSignals: string[];
  existing: boolean;
  rootDataset: string | null;
  installUuid: string | null;
}

export interface ResolvedInstallMode {
  requested: FirstBootInstallMode;
  effective: 'fresh' | 'upgrade' | 'rescue';
  detection: ExistingInstallDetection;
}

interface DetectorDeps {
  existsSync: (filePath: string) => boolean;
  readdirSync: (filePath: string) => string[];
  execFileSync: typeof execFileSync;
  commandExists: (name: string) => boolean;
}

const DEFAULT_DEPS: DetectorDeps = {
  existsSync: fs.existsSync,
  readdirSync: (filePath) => fs.readdirSync(filePath),
  execFileSync,
  commandExists,
};

function hasProjectEnv(projectRoot: string, deps: DetectorDeps): boolean {
  const envFile = path.join(projectRoot, '.env');
  if (!deps.existsSync(envFile)) return false;
  try {
    const content = fs.readFileSync(envFile, 'utf-8');
    return content
      .split('\n')
      .map((line) => line.trim())
      .some((line) => line && !line.startsWith('#'));
  } catch {
    return false;
  }
}

function hasNonEmptyGroupsDir(projectRoot: string, deps: DetectorDeps): boolean {
  const groupsDir = path.join(projectRoot, 'groups');
  if (!deps.existsSync(groupsDir)) return false;
  try {
    return deps.readdirSync(groupsDir).some((entry) => !entry.startsWith('.'));
  } catch {
    return false;
  }
}

function hasInstalledService(deps: DetectorDeps): boolean {
  return deps.existsSync(`/usr/local/etc/rc.d/${SERVICE_NAME}`);
}

function hasRuntimeUser(deps: DetectorDeps): boolean {
  try {
    deps.execFileSync('id', ['-u', SERVICE_NAME], {
      stdio: ['ignore', 'ignore', 'ignore'],
    });
    return true;
  } catch {
    return false;
  }
}

function hasZfsDataset(projectRoot: string, deps: DetectorDeps): boolean {
  if (!deps.commandExists('zfs')) return false;
  try {
    const systemEnv = loadSystemEnv(projectRoot, deps);
    const zfsPrefix = systemEnv.zfsPrefix || ZFS_PREFIX;
    const exactDataset =
      systemEnv.zfsPool && zfsPrefix
        ? `${systemEnv.zfsPool}/${zfsPrefix}`
        : null;
    const output = deps.execFileSync('zfs', ['list', '-H', '-o', 'name'], {
      encoding: 'utf-8',
      stdio: ['ignore', 'pipe', 'ignore'],
    });
    const datasets = output
      .split('\n')
      .map((line) => line.trim())
      .filter(Boolean);
    return datasets.some(
      (name) =>
        (exactDataset
          ? name === exactDataset ||
            name.startsWith(`${exactDataset}/`) ||
            name.endsWith(`${exactDataset}@`)
          : false) ||
        name.endsWith(`/${zfsPrefix}`) ||
        name === zfsPrefix ||
        name.includes(`/${zfsPrefix}/`) ||
        name.endsWith(`/${zfsPrefix}/pgdata`),
    );
  } catch {
    return false;
  }
}

function getZfsInstallUuid(
  projectRoot: string,
  deps: DetectorDeps,
): { rootDataset: string | null; installUuid: string | null } {
  if (!deps.commandExists('zfs')) {
    return { rootDataset: null, installUuid: null };
  }
  try {
    const root = resolvePlatformRootDataset(projectRoot, deps);
    const metadata = getZfsMetadata(root.dataset, ['install-uuid'], deps);
    return {
      rootDataset: root.dataset,
      installUuid: metadata['install-uuid'],
    };
  } catch {
    return { rootDataset: null, installUuid: null };
  }
}

export function detectExistingInstall(
  projectRoot: string,
  deps: Partial<DetectorDeps> = {},
): ExistingInstallDetection {
  const resolvedDeps = { ...DEFAULT_DEPS, ...deps };
  const signals: ExistingInstallSignals = {
    envFile: hasProjectEnv(projectRoot, resolvedDeps),
    groupsDir: hasNonEmptyGroupsDir(projectRoot, resolvedDeps),
    serviceFile: hasInstalledService(resolvedDeps),
    zfsDataset: hasZfsDataset(projectRoot, resolvedDeps),
    zfsMetadata: false,
    runtimeUser: hasRuntimeUser(resolvedDeps),
  };
  const zfsIdentity = getZfsInstallUuid(projectRoot, resolvedDeps);
  signals.zfsMetadata = Boolean(zfsIdentity.installUuid);

  const strongSignals: string[] = [];
  const softSignals: string[] = [];

  if (signals.serviceFile) strongSignals.push('service');
  if (signals.zfsDataset) strongSignals.push('zfs');
  if (signals.zfsMetadata) strongSignals.push('zfs-metadata');
  if (signals.runtimeUser) strongSignals.push('runtime-user');
  if (signals.envFile) softSignals.push('env');
  if (signals.groupsDir) softSignals.push('groups');

  const existing = strongSignals.length > 0 || softSignals.length >= 2;

  return {
    signals,
    strongSignals,
    softSignals,
    existing,
    rootDataset: zfsIdentity.rootDataset,
    installUuid: zfsIdentity.installUuid,
  };
}

export function resolveInstallMode(
  requested: FirstBootInstallMode,
  detection: ExistingInstallDetection,
): ResolvedInstallMode {
  if (requested === 'auto') {
    return {
      requested,
      effective: detection.existing ? 'upgrade' : 'fresh',
      detection,
    };
  }

  if (requested === 'fresh' && detection.existing) {
    const found = [...detection.strongSignals, ...detection.softSignals].join(', ');
    throw new Error(
      `INSTALL_MODE=fresh refused: existing install detected (${found || 'signals present'}). Use INSTALL_MODE=upgrade or INSTALL_MODE=rescue, or remove the existing installation first.`,
    );
  }

  if ((requested === 'upgrade' || requested === 'rescue') && !detection.existing) {
    throw new Error(
      `INSTALL_MODE=${requested} refused: no existing install detected. Use INSTALL_MODE=auto or INSTALL_MODE=fresh for a new machine.`,
    );
  }

  return {
    requested,
    effective: requested,
    detection,
  };
}