// `Incremental` contains multiple maps for the different parts of a site
// build, and tracks reused items across builds. It also handles emitting and
// updating the built site. This structure is self contained and serializable.
//
// Tracking is simple: Files map to one or more 'source IDs', which map to one
// or more 'artifact'. This two layer approach allows many files (say a page +
// all its imports) to map to the build of a page, which produces an HTML file
// plus a list of scripts.

import { Buffer } from "node:buffer";
interface ArtifactMap {
  asset: Asset;
  script: string;
}
type AllArtifactMaps = {
  [K in keyof ArtifactMap]: Map<string, ArtifactMap[K]>;
};
type ArtifactType = keyof ArtifactMap;

interface Asset {
  buffer: Buffer;
  headers: Record<string, string | undefined>;
  hash: string;
}

export interface PutBase {
  srcTag?: string; // deprecated
  srcId: string;
  key: string;
}

export interface Put<T extends ArtifactType> extends PutBase {
  type: T;
  value: ArtifactMap[T];
}

export interface Output {
  type: ArtifactType;
  key: string;
}

const gzip = util.promisify(zlib.gzip);
const zstd = util.promisify(zlib.zstdCompress);

export class Incremental {
  /** The generated artifacts */
  out: AllArtifactMaps = {
    asset: new Map(),
    script: new Map(),
  };
  /** Compressed resources */
  compress = new Map<string, Compressed>();
  compressQueue = new Queue<CompressJob, void>({
    name: "Compress",
    maxJobs: 5,
    fn: this.compressImpl.bind(this),
    passive: true,
    getItemText: (job) => `${job.algo.toUpperCase()} ${job.label}`,
  });
  /** Tracking filesystem entries to `srcId` */
  files = new Map<string, hot.FileStat>();
  srcIds = new Map<string, Output[]>();

  static fromSerialized() {
  }
  serialize() {
    const writer = new BufferWriter();

    const asset = Array.from(
      this.out.asset,
      ([key, { buffer, hash, headers }]) => {
        const raw = writer.write(buffer, hash);
        const { gzip: gzipBuf, zstd: zstdBuf } = this.compress.get(hash) ?? {};
        const gzip = gzipBuf ? writer.write(gzipBuf, hash) : null;
        const zstd = zstdBuf ? writer.write(zstdBuf, hash) : null;
        return [key, {
          raw,
          gzip,
          zstd,
          hash,
          headers,
        }];
      },
    );
    const script = Array.from(this.out.script);

    const meta = Buffer.from(
      JSON.stringify({
        asset,
        script,
      }),
      "utf-8",
    );

    const lengthBuffer = Buffer.alloc(4);
    lengthBuffer.writeUInt32LE(meta.byteLength, 0);

    return Buffer.concat([meta, lengthBuffer, ...writer.buffers]);
  }

  serializeToDisk(file = ".clover/incr.state") {
    const buffer = this.serialize();
    fs.writeFileSync(file, buffer);
  }

  put<T extends ArtifactType>({
    srcId,
    type,
    key,
    value,
  }: Put<T>) {
    this.out[type].set(key, value);
  }

  async putAsset(info: PutAsset) {
    const { body, headers, key } = info;
    const buffer = Buffer.isBuffer(body) ? body : Buffer.from(body);
    const hash = Buffer.from(await crypto.subtle.digest("sha-1", buffer))
      .toString("hex");
    const value: Asset = {
      buffer,
      headers: {
        "Content-Type": headers?.["Content-Type"] ?? mime.contentTypeFor(key),
        "ETag": JSON.stringify(hash),
        ...headers,
      },
      hash,
    };
    if (!this.compress.has(hash)) {
      const label = info.key;
      this.compress.set(hash, {
        zstd: undefined,
        gzip: undefined,
      });
      await Promise.all([
        this.compressQueue.add({ label, buffer, algo: "zstd", hash }),
        this.compressQueue.add({ label, buffer, algo: "gzip", hash }),
      ]);
    }
    return this.put({ ...info, type: "asset", value });
  }

  async compressImpl({ algo, buffer, hash }: CompressJob) {
    let out;
    switch (algo) {
      case "zstd":
        out = await zstd(buffer);
        break;
      case "gzip":
        out = await gzip(buffer, { level: 9 });
        break;
    }
    let entry = this.compress.get(hash);
    if (!entry) {
      this.compress.set(
        hash,
        entry = {
          zstd: undefined,
          gzip: undefined,
        },
      );
    }
    entry![algo] = out;
  }

  invalidate(srcId: string) {
  }

  async wait() {
    await this.compressQueue.done({ method: "stop" });
  }
  async flush() {
    const writer = new BufferWriter();
    const asset = Object.fromEntries(
      Array.from(this.out.asset, ([key, { buffer, hash, headers }]) => {
        const raw = writer.write(buffer, hash);
        const { gzip: gzipBuf, zstd: zstdBuf } = this.compress.get(hash) ?? {};
        const gzip = gzipBuf ? writer.write(gzipBuf, hash) : null;
        const zstd = zstdBuf ? writer.write(zstdBuf, hash) : null;
        return [key, {
          raw,
          gzip,
          zstd,
          headers,
        }];
      }),
    );
    await Promise.all([
      fs.writeFile(".clover/static.json", JSON.stringify(asset)),
      fs.writeFile(".clover/static.blob", writer.get()),
    ]);
  }
}

export interface PutAsset extends PutBase {
  body: string | Buffer;
  headers?: Record<string, string | undefined>;
}

export interface Compressed {
  gzip?: Buffer;
  zstd?: Buffer;
}

export interface CompressJob {
  algo: "zstd" | "gzip";
  buffer: Buffer;
  label: string;
  hash: string;
}

class BufferWriter {
  size = 0;
  seen = new Map<string, View>();
  buffers: Buffer[] = [];

  write(buffer: Buffer, hash: string): View {
    let view = this.seen.get(hash);
    if (view) return view;
    view = [this.size, this.size += buffer.byteLength];
    this.seen.set(hash, view);
    this.buffers.push(buffer);
    return view;
  }

  get() {
    return Buffer.concat(this.buffers);
  }
}

export type View = [start: number, end: number];

// Alongside this type is a byte buffer, containing all the assets.
export interface BuiltAssetMap {
  [route: string]: BuiltAsset;
}
export interface BuiltAsset {
  raw: View;
  gzip: View;
  zstd: View;
  headers: Record<string, string>;
}

export interface SerializedMeta {
  asset: Array<[route: string, data: {
    raw: View;
    gzip: View | null;
    zstd: View | null;
    hash: string;
    headers: Record<string, string>;
  }]>;
  script: [key: string, value: string][];
}

function never(): never {
  throw new Error("Impossible");
}

import * as path from "node:path";
import * as fs from "./fs.ts";
import * as zlib from "node:zlib";
import * as util from "node:util";
import { Queue } from "./queue.ts";
import * as hot from "./hot.ts";
import * as mime from "./mime.ts";