import fs from "node:fs/promises";
import path from "node:path";
import { manifestPath } from "./paths.ts";
import { readIfExists, sha256, writeAtomic } from "./fsx.ts";
import { extractBlock } from "./marker.ts";
import type { DriftReport, InstallRecord, Manifest, Scope, TargetId } from "./types.ts";

const EMPTY: Manifest = { schema: 1, installs: [] };

export async function readManifest(home?: string): Promise<Manifest> {
  const raw = await readIfExists(manifestPath(home));
  if (!raw) return structuredClone(EMPTY);
  try {
    const parsed = JSON.parse(raw) as Manifest;
    if (parsed.schema !== 1 || !Array.isArray(parsed.installs)) return structuredClone(EMPTY);
    return parsed;
  } catch {
    // 손상된 매니페스트로 설치 전체가 막히지 않도록 빈 것으로 되돌린다
    return structuredClone(EMPTY);
  }
}

export async function writeManifest(m: Manifest, home?: string): Promise<void> {
  await writeAtomic(manifestPath(home), JSON.stringify(m, null, 2) + "\n");
}

function sameInstall(a: InstallRecord, target: TargetId, scope: Scope, root: string): boolean {
  return a.target === target && a.scope === scope && path.resolve(a.root) === path.resolve(root);
}

export function findInstall(
  m: Manifest,
  target: TargetId,
  scope: Scope,
  root: string,
): InstallRecord | undefined {
  return m.installs.find((i) => sameInstall(i, target, scope, root));
}

export async function upsertInstall(record: InstallRecord, home?: string): Promise<void> {
  const m = await readManifest(home);
  const idx = m.installs.findIndex((i) => sameInstall(i, record.target, record.scope, record.root));
  if (idx >= 0) m.installs[idx] = record;
  else m.installs.push(record);
  await writeManifest(m, home);
}

export async function dropInstall(
  target: TargetId,
  scope: Scope,
  root: string,
  home?: string,
): Promise<void> {
  const m = await readManifest(home);
  m.installs = m.installs.filter((i) => !sameInstall(i, target, scope, root));
  await writeManifest(m, home);
}

/**
 * 설치 당시 해시와 현재 내용을 비교한다.
 * 마커 방식 파일은 문서 전체가 아니라 블록 안쪽만 비교한다 — 사용자가 문서의 다른 부분을
 * 고치는 것은 정상이고, 그걸 드리프트로 잡으면 update 가 영영 못 돈다.
 */
export async function inspectDrift(record: InstallRecord): Promise<DriftReport> {
  const files: DriftReport["files"] = [];
  for (const f of record.files) {
    const cur = await readIfExists(f.path);
    if (cur === null) {
      files.push({ path: f.path, status: "missing" });
      continue;
    }
    const target = f.marker ? (extractBlock(cur, f.marker) ?? "") : cur;
    files.push({ path: f.path, status: sha256(target) === f.sha256 ? "ok" : "modified" });
  }
  return {
    record,
    files,
    modified: files.filter((f) => f.status === "modified").map((f) => f.path),
  };
}

/** 매니페스트가 가리키는 경로가 실제로 살아있는지 확인한다 */
export async function pruneDeadInstalls(home?: string): Promise<number> {
  const m = await readManifest(home);
  const before = m.installs.length;
  const alive: InstallRecord[] = [];
  for (const rec of m.installs) {
    const anyAlive = await Promise.all(
      rec.files.map(async (f) => {
        try {
          await fs.access(f.path);
          return true;
        } catch {
          return false;
        }
      }),
    );
    if (anyAlive.some(Boolean)) alive.push(rec);
  }
  if (alive.length !== before) {
    m.installs = alive;
    await writeManifest(m, home);
  }
  return before - alive.length;
}
