import { createHash, randomUUID } from "node:crypto";
import fs from "node:fs/promises";
import path from "node:path";
import type { SkillProposal, SkillWorkshopStatus } from "./types.js";

type StoreFile = {
  version: 1;
  proposals: SkillProposal[];
  review?: SkillWorkshopReviewState;
};

type SkillWorkshopReviewState = {
  turnsSinceReview: number;
  toolCallsSinceReview: number;
  lastReviewAt?: number;
};

const locks = new Map<string, Promise<void>>();

function workspaceKey(workspaceDir: string): string {
  return createHash("sha256").update(path.resolve(workspaceDir)).digest("hex").slice(0, 16);
}

async function withLock<T>(key: string, task: () => Promise<T>): Promise<T> {
  const previous = locks.get(key) ?? Promise.resolve();
  let release: (() => void) | undefined;
  const next = new Promise<void>((resolve) => {
    release = resolve;
  });
  locks.set(
    key,
    previous.then(() => next),
  );
  await previous;
  try {
    return await task();
  } finally {
    release?.();
    if (locks.get(key) === next) {
      locks.delete(key);
    }
  }
}

async function readJson(filePath: string): Promise<StoreFile> {
  try {
    const raw = await fs.readFile(filePath, "utf8");
    const parsed = JSON.parse(raw) as StoreFile;
    return {
      version: 1,
      proposals: Array.isArray(parsed.proposals) ? parsed.proposals : [],
      review:
        parsed.review && typeof parsed.review === "object"
          ? normalizeReviewState(parsed.review as Partial<SkillWorkshopReviewState>)
          : undefined,
    };
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code === "ENOENT") {
      return { version: 1, proposals: [] };
    }
    throw error;
  }
}

function normalizeReviewState(
  value: Partial<SkillWorkshopReviewState> = {},
): SkillWorkshopReviewState {
  return {
    turnsSinceReview:
      typeof value.turnsSinceReview === "number" && Number.isFinite(value.turnsSinceReview)
        ? Math.max(0, Math.trunc(value.turnsSinceReview))
        : 0,
    toolCallsSinceReview:
      typeof value.toolCallsSinceReview === "number" && Number.isFinite(value.toolCallsSinceReview)
        ? Math.max(0, Math.trunc(value.toolCallsSinceReview))
        : 0,
    ...(typeof value.lastReviewAt === "number" && Number.isFinite(value.lastReviewAt)
      ? { lastReviewAt: value.lastReviewAt }
      : {}),
  };
}

async function atomicWriteJson(filePath: string, data: StoreFile): Promise<void> {
  await fs.mkdir(path.dirname(filePath), { recursive: true });
  const tempPath = `${filePath}.tmp-${process.pid}-${Date.now().toString(36)}-${randomUUID()}`;
  await fs.writeFile(tempPath, `${JSON.stringify(data, null, 2)}\n`, "utf8");
  await fs.rename(tempPath, filePath);
}

export class SkillWorkshopStore {
  readonly filePath: string;

  constructor(params: { stateDir: string; workspaceDir: string }) {
    this.filePath = path.join(
      params.stateDir,
      "skill-workshop",
      `${workspaceKey(params.workspaceDir)}.json`,
    );
  }

  async list(status?: SkillWorkshopStatus): Promise<SkillProposal[]> {
    const file = await readJson(this.filePath);
    const proposals = status
      ? file.proposals.filter((proposal) => proposal.status === status)
      : file.proposals;
    return proposals.toSorted((left, right) => right.createdAt - left.createdAt);
  }

  async get(id: string): Promise<SkillProposal | undefined> {
    return (await this.list()).find((proposal) => proposal.id === id);
  }

  async add(proposal: SkillProposal, maxPending: number): Promise<SkillProposal> {
    return await withLock(this.filePath, async () => {
      const file = await readJson(this.filePath);
      const duplicate = file.proposals.find(
        (item) =>
          (item.status === "pending" || item.status === "quarantined") &&
          item.skillName === proposal.skillName &&
          JSON.stringify(item.change) === JSON.stringify(proposal.change),
      );
      if (duplicate) {
        return duplicate;
      }
      const nextProposals = [proposal, ...file.proposals].filter((item, index, all) => {
        if (item.status !== "pending" && item.status !== "quarantined") {
          return true;
        }
        return (
          all
            .slice(0, index + 1)
            .filter(
              (candidate) => candidate.status === "pending" || candidate.status === "quarantined",
            ).length <= maxPending
        );
      });
      await atomicWriteJson(this.filePath, { ...file, version: 1, proposals: nextProposals });
      return proposal;
    });
  }

  async updateStatus(id: string, status: SkillWorkshopStatus): Promise<SkillProposal> {
    return await withLock(this.filePath, async () => {
      const file = await readJson(this.filePath);
      const index = file.proposals.findIndex((proposal) => proposal.id === id);
      if (index < 0) {
        throw new Error(`proposal not found: ${id}`);
      }
      const updated = { ...file.proposals[index], status, updatedAt: Date.now() };
      file.proposals[index] = updated;
      await atomicWriteJson(this.filePath, file);
      return updated;
    });
  }

  async recordReviewTurn(toolCalls: number): Promise<SkillWorkshopReviewState> {
    return await withLock(this.filePath, async () => {
      const file = await readJson(this.filePath);
      const current = normalizeReviewState(file.review);
      const next = {
        ...current,
        turnsSinceReview: current.turnsSinceReview + 1,
        toolCallsSinceReview: current.toolCallsSinceReview + Math.max(0, Math.trunc(toolCalls)),
      };
      await atomicWriteJson(this.filePath, { ...file, review: next });
      return next;
    });
  }

  async markReviewed(): Promise<SkillWorkshopReviewState> {
    return await withLock(this.filePath, async () => {
      const file = await readJson(this.filePath);
      const next = {
        turnsSinceReview: 0,
        toolCallsSinceReview: 0,
        lastReviewAt: Date.now(),
      };
      await atomicWriteJson(this.filePath, { ...file, review: next });
      return next;
    });
  }
}