/**
 * GlobalSidecarStore — the out-of-workspace/untitled authoring sidecar (F8 spec
 * §6.2/§6.4), mirroring BaselineStore (src/baselineStore.ts): vscode-free (Node
 * fs/crypto only), one `Artifact` JSON per document in VS Code's per-extension
 * GLOBAL storage, NEVER the repo (INV-19/24). The key passed in is the DOCUMENT
 * KEY (the URI string for the docs this store serves):
 *   - `file:` URI  → disk at `<dir>/sidecars/<sha256(uri)>.json`.
 *   - `untitled:`  → an in-memory Map only (no durable identity — the F6
 *     degrade); lost on reload, and never read by mergeArtifacts (INV-25).
 * `consumeSelfWrite` is a no-op (these artifacts are outside the `.threads/`
 * watcher, so there is no self-write storm to suppress).
 */
import * as fs from "node:fs";
import * as path from "node:path";
import { createHash } from "node:crypto";
import {
  SCHEMA_VERSION,
  emptyArtifact,
  isNewerMajor,
  serializeArtifact,
  type Artifact,
} from "./model";
import type { SidecarStore } from "./sidecarStore";

export class GlobalSidecarStore implements SidecarStore {
  /** untitled keys live here only — no durable identity to persist against. */
  private readonly memory = new Map<string, Artifact>();

  /** @param storageDir absolute VS Code GLOBAL-storage dir (context.globalStorageUri.fsPath). */
  constructor(private readonly storageDir: string) {}

  private isUntitled(key: string): boolean {
    return key.startsWith("untitled:");
  }

  /** Filesystem-safe storage key for a persistable (file:) doc: sha256 of its URI. */
  private storageKey(key: string): string {
    return createHash("sha256").update(key).digest("hex");
  }

  /** Disk path for a `file:` key, or undefined for an in-memory untitled key. */
  sidecarPath(key: string): string | undefined {
    if (this.isUntitled(key)) return undefined;
    return path.join(this.storageDir, "sidecars", `${this.storageKey(key)}.json`);
  }

  load(key: string): Artifact | null {
    if (this.isUntitled(key)) return this.memory.get(key) ?? null;
    const p = this.sidecarPath(key)!;
    if (!fs.existsSync(p)) return null;
    return JSON.parse(fs.readFileSync(p, "utf8")) as Artifact;
  }

  save(key: string, artifact: Artifact): void {
    if (this.isUntitled(key)) {
      this.memory.set(key, artifact);
      return;
    }
    const p = this.sidecarPath(key)!;
    fs.mkdirSync(path.dirname(p), { recursive: true });
    fs.writeFileSync(p, serializeArtifact(artifact), "utf8");
  }

  /** See CoauthorStore.update — same INV-16 throw + anchor prune, no self-write mark. */
  update(key: string, mutate: (artifact: Artifact) => void): Artifact {
    const artifact = this.load(key) ?? emptyArtifact(key);
    if (isNewerMajor(artifact)) {
      throw new Error(
        `refusing to write ${key}: sidecar schemaVersion ${artifact.schemaVersion} > supported ${SCHEMA_VERSION} (INV-16)`,
      );
    }
    mutate(artifact);
    const referenced = new Set<string>([
      ...artifact.threads.map((t) => t.anchorId),
      ...artifact.attributions.map((a) => a.anchorId),
      ...artifact.proposals.map((p) => p.anchorId),
    ]);
    for (const id of Object.keys(artifact.anchors)) {
      if (!referenced.has(id)) delete artifact.anchors[id];
    }
    this.save(key, artifact);
    return artifact;
  }

  /** No-op: global artifacts are outside the `.threads/` watcher. */
  consumeSelfWrite(_fsPath: string): boolean {
    return false;
  }
}