// Incremental contains multiple maps for the different kinds
// of Artifact, which contain a list of source files which
// were used to produce it. When files change, Incremental sees
// that the `mtime` is newer, and purges the referenced artifacts.

type SourceId = string; // relative to project root, e.g. 'src/global.css'
type ArtifactId = string; // `${ArtifactType}\0${string}`
type Sha1Id = string; // Sha1 hex string

// -- artifact types --
interface ArtifactMap {
  /* An asset (serve with "#sitegen/asset" */
  asset: Asset;
  /* The bundled text of a '.client.ts' script */
  // TODO: track imports this has into `asset`
  script: string;
  /* The bundled style tag contents. Keyed by 'css.styleKey' */
  style: string;
  /* Metadata about a static page */
  pageMetadata: PageMetadata;
  /* Metadata about a dynamic view */
  viewMetadata: ViewMetadata;
}
type ArtifactKind = keyof ArtifactMap;
export interface Asset {
  buffer: Buffer;
  headers: Record<string, string | undefined>;
  hash: string;
}
/**
 * This interface intentionally omits the *contents*
 * of its scripts and styles for fine-grained rebuilds.
 */
export interface PageMetadata {
  html: string;
  meta: string;
  cssImports: string[];
  theme: css.Theme;
  clientRefs: string[];
}
/**
 * Like a page, this intentionally omits resources,
 * but additionally omits the bundled server code.
 */
export interface ViewMetadata {
  file: string;
  // staticMeta: string | null; TODO
  cssImports: string[];
  theme: css.Theme;
  clientRefs: string[];
  hasLayout: boolean;
}

// -- incremental support types --
export interface PutBase {
  sources: SourceId[];
  key: string;
}
export interface Put<T extends ArtifactKind> extends PutBase {
  kind: T;
  value: ArtifactMap[T];
}
export interface Invalidations {
  lastModified: number;
  outputs: Set<ArtifactId>;
  files: Set<SourceId>;
}

export class Incremental {
  /** The generated artifacts */
  out: {
    [K in keyof ArtifactMap]: Map<string, ArtifactMap[K]>;
  } = {
    asset: new Map(),
    script: new Map(),
    style: new Map(),
    pageMetadata: new Map(),
    viewMetadata: new Map(),
  };
  /** Tracking filesystem entries to `srcId` */
  invals = new Map<SourceId, Invalidations>();
  /** Tracking output keys to files */
  sources = new Map<ArtifactId, SourceId[]>();

  /** Compressed resources */
  compress = new Map<Sha1Id, Compressed>();
  compressQueue = new Queue<CompressJob, void>({
    name: "Compress",
    maxJobs: 5,
    fn: this.compressImpl.bind(this),
    passive: true,
    getItemText: (job) => `${job.algo.toUpperCase()} ${job.label}`,
  });

  getArtifact<T extends ArtifactKind>(kind: T, key: string) {
    return this.out[kind].get(key);
  }

  hasArtifact<T extends ArtifactKind>(kind: T, key: string) {
    return this.out[kind].has(key);
  }

  sourcesFor(kind: ArtifactKind, key: string) {
    return UNWRAP(this.sources.get(kind + "\0" + key));
  }

  /*
   * Put built artifacts into the incremental cache. The entry points
   * used to build this must be provided. 'Incremental' will trace JS
   * imports and file modification times tracked by 'hot.ts'.
   */
  put<T extends ArtifactKind>({
    sources,
    kind,
    key,
    value,
  }: Put<T>) {
    console.log("put " + kind + ": " + key);
    this.out[kind].set(key, value);

    // Update sources information
    ASSERT(sources.length > 0, "Missing sources for " + kind + " " + key);
    sources = sources.map((src) => path.normalize(src));
    const fullKey = `${kind}\0${key}`;
    const prevSources = this.sources.get(fullKey);
    const newSources = new Set(
      sources.map((file) =>
        path.isAbsolute(file) ? path.relative(hot.projectRoot, file) : file
      ),
    );
    this.sources.set(fullKey, [...newSources]);
    for (const source of prevSources ?? []) {
      if (sources.includes(source)) {
        newSources.delete(source);
        continue;
      }
      const invals = UNWRAP(this.invals.get(source));
      ASSERT(invals.outputs.has(fullKey));
      invals.outputs.delete(fullKey);
    }
    // Use reflection from the plugin system to get imports.
    for (const source of newSources) {
      const invals = this.#getOrInitInvals(source);
      invals.outputs.add(fullKey);
      this.#followImports(source);
    }
  }

  // TODO: this doesnt remove stuff when it disappeary
  #getOrInitInvals(source: string) {
    let invals = this.invals.get(source);
    if (!invals) {
      const g = hot.getFsGraph().get(source);
      const lastModified = g?.lastModified ??
        fs.statSync(path.resolve(hot.projectRoot, source)).mtimeMs;
      this.invals.set(
        source,
        invals = {
          lastModified,
          files: new Set(),
          outputs: new Set(),
        },
      );
    }
    return invals;
  }

  #followImports(file: string) {
    const graph = hot.getFsGraph();
    const stat = graph.get(file);
    if (!stat) return;
    for (const i of stat.imports) {
      const invals = this.#getOrInitInvals(i);
      invals.files.add(file);
      this.#followImports(i);
    }
  }

  async statAllFiles() {
    for (const file of this.invals.keys()) {
      const mtime = fs.statSync(file).mtimeMs;
      this.updateStat(file, mtime);
    }
  }

  updateStat(file: string, newLastModified: number) {
    file = path.relative(hot.projectRoot, file);
    const stat = this.invals.get(file);
    ASSERT(stat, "Updated stat on untracked file " + file);
    const hasUpdate = stat.lastModified < newLastModified;
    if (hasUpdate) {
      // Invalidate
      console.info(file + " updated");
      const invalidQueue = [file];
      let currentInvalid;
      while (currentInvalid = invalidQueue.pop()) {
        const invalidations = this.invals.get(currentInvalid);
        ASSERT(
          invalidations,
          "No reason to track file '" + currentInvalid +
            "' if it has no invalidations",
        );
        const { files, outputs } = invalidations;
        for (const out of outputs) {
          const [kind, artifactKey] = out.split("\0");
          this.out[kind as ArtifactKind].delete(artifactKey);
          console.log("stale " + kind + ": " + artifactKey);
        }
        invalidQueue.push(...files);
      }
    }
    stat.lastModified = newLastModified;
    return hasUpdate;
  }

  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,
    };
    const a = this.put({ ...info, kind: "asset", value });
    if (!this.compress.has(hash)) {
      const label = info.key;
      this.compress.set(hash, {
        zstd: undefined,
        gzip: undefined,
      });
      this.compressQueue.add({ label, buffer, algo: "zstd", hash });
      this.compressQueue.add({ label, buffer, algo: "gzip", hash });
    }
    return a;
  }

  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;
  }

  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 + ".gz") : null;
        const zstd = zstdBuf ? writer.write(zstdBuf, hash + ".zstd") : null;
        return [key, {
          raw,
          gzip,
          zstd,
          hash,
          headers: headers as Record<string, string>,
        }] satisfies SerializedMeta["asset"][0];
      },
    );
    const script = Array.from(this.out.script);
    const invals = Array.from(this.invals, ([key, value]) => {
      const { lastModified, files, outputs } = value;
      return [key, {
        m: lastModified,
        f: [...files],
        o: [...outputs],
      }] satisfies SerializedMeta["invals"][0];
    });
    const sources = Array.from(this.sources, ([key, value]) => {
      return [key, ...value] as [string, ...string[]];
    });
    const json = {
      asset,
      script,
      invals,
      sources,
    } satisfies SerializedMeta;
    const meta = Buffer.from(JSON.stringify(json), "utf-8");

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

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

  static fromSerialized(buffer: Buffer): Incremental {
    const metaLength = buffer.readUint32LE(0);
    const meta: SerializedMeta = JSON.parse(
      buffer.subarray(4, 4 + metaLength).toString("utf8"),
    );
    const view = ([start, end]: View) =>
      buffer.subarray(4 + metaLength + start, 4 + metaLength + end);

    const incr = new Incremental();
    incr.out.asset = new Map<string, Asset>(meta.asset.map(([key, value]) => {
      const { hash, raw, gzip, zstd, headers } = value;
      if ((gzip || zstd) && !incr.compress.has(hash)) {
        incr.compress.set(hash, {
          gzip: gzip ? view(gzip) : undefined,
          zstd: zstd ? view(zstd) : undefined,
        });
      }
      return [key, {
        buffer: view(raw),
        headers: headers,
        hash: hash,
      }];
    }));
    incr.out.script = new Map(meta.script);
    incr.invals = new Map(meta.invals.map(([key, { m, f, o }]) => {
      return [key, {
        lastModified: m,
        files: new Set(f),
        outputs: new Set(o),
      }];
    }));
    incr.sources = new Map(meta.sources.map(([key, ...value]) => [key, value]));
    return incr;
  }

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

  static fromDisk(file = ".clover/incr.state"): Incremental {
    try {
      const buffer = fs.readFileSync(file);
      return Incremental.fromSerialized(buffer);
    } catch (err: any) {
      if (err.code === "ENOENT") return new Incremental();
      throw err;
    }
  }

  async wait() {
    await this.compressQueue.done({ method: "success" });
  }

  async flush() {
    ASSERT(!this.compressQueue.active);
    const writer = new BufferWriter();
    // TODO: ensure all assets are actually compressed and not fake lying.
    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 + ".gz") : null;
        const zstd = zstdBuf ? writer.write(zstdBuf, hash + ".zstd") : 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];

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: Array<[key: string, value: string]>;
  invals: Array<[key: string, {
    /** Modified */
    m: number;
    f: SourceId[];
    o: ArtifactId[];
  }]>;
  sources: Array<[string, ...string[]]>;
}

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

import * as fs from "#sitegen/fs";
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 "#sitegen/mime";
import * as path from "node:path";
import { Buffer } from "node:buffer";
import * as css from "./css.ts";