/**
 * BaselineStore — load/save one diff-view baseline JSON per document (F6 §6.3).
 * The CoauthorStore shape (src/store.ts): vscode-free (Node fs only, unit-
 * testable), one file per storage key. INV-19: the storage dir is VS Code's
 * per-extension GLOBAL storage, NEVER the repo — so the baseline can never be
 * committed, merged, or read by another rung. F6 works on *any* file, so the
 * key is a hash of the document URI (the controller derives it), not a
 * workspace-relative path; an untitled buffer has no durable identity and is
 * never persisted here (in-memory only — see DiffViewController).
 *
 * INV-7 (native-surfaces migration, spec §6.4): the baseline is now either the
 * git-HEAD blob (never persisted — see GitBaselineAdapter/DiffViewController)
 * or a snapshot captured on coediting-entry / re-pinned by "Mark Changes as
 * Reviewed". `"opened"`/`"machine-landing"` are legacy reasons from the
 * shipped #17/#48 baseline; `normalizeReason` migrates them on load so old
 * on-disk baselines keep round-tripping under the new vocabulary.
 */
import * as fs from "node:fs";
import * as path from "node:path";

export type BaselineReason = "entered" | "pinned" | "head";
type LegacyBaselineReason = BaselineReason | "opened" | "machine-landing";

export interface Baseline {
  /** the document URI (the identity the key is derived from) — for round-trip/debug. */
  uri: string;
  /** full document text captured at the epoch (from the buffer, not disk — §6.3). */
  text: string;
  capturedAt: string;
  reason: BaselineReason;
}

/** Migrate legacy on-disk reasons to the current vocabulary (§6.4 INV-7). */
export function normalizeReason(reason: LegacyBaselineReason): BaselineReason {
  if (reason === "opened" || reason === "machine-landing") return "entered";
  return reason;
}

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

  /** `<storageDir>/baselines/<key>.json` — `key` is a filesystem-safe hash (§6.3). */
  baselinePath(key: string): string {
    return path.join(this.storageDir, "baselines", `${key}.json`);
  }

  load(key: string): Baseline | null {
    const p = this.baselinePath(key);
    if (!fs.existsSync(p)) return null;
    const raw = JSON.parse(fs.readFileSync(p, "utf8")) as Baseline;
    return { ...raw, reason: normalizeReason(raw.reason) };
  }

  /** Newest epoch wins — overwrite in place, no history (state-not-history, the F3/F4 precedent). */
  save(key: string, baseline: Baseline): void {
    const p = this.baselinePath(key);
    fs.mkdirSync(path.dirname(p), { recursive: true });
    fs.writeFileSync(p, JSON.stringify(baseline, null, 2) + "\n", "utf8");
  }
}