import type { SyncOperationInput, SyncResponse } from "@/lib/sync/envelope";
import { ctxKeyOf, type BlobEntry, type BlobKind, type OfflineContext, type OfflineStore, type OutboxEntry, type OutboxError } from "./types";
import {
  applyResults,
  applyTransportFailure,
  backoffMs,
  blobRef,
  createEntry,
  MAX_BATCH,
  recoverSending,
  selectBatch,
  selectUploads,
  type QueuedOpInput,
} from "./outbox-core";

/**
 * One synchronisation pass over the outbox of a context (lane L7). Environment-free: storage and
 * network are injected, so the same code runs in the browser (outbox.ts: IndexedDB + fetch) and in
 * the tests (memory store + in-process applyOperations).
 */

export type BatchOutcome = { ok: true; response: SyncResponse } | { ok: false; error: "network" | "unauthorized" | "internal" };
export type UploadOutcome = { ok: true; documentId: string } | { ok: false; error: "network" | "unauthorized" | "invalid" | "forbidden" | "not_found" | "internal" };

export type Transport = {
  sendBatch(deviceId: string, operations: SyncOperationInput[]): Promise<BatchOutcome>;
  upload(blob: BlobEntry): Promise<UploadOutcome>;
};

export type EngineDeps = {
  store: OfflineStore;
  ctx: OfflineContext;
  transport: Transport;
  deviceId: string;
  now?: () => Date;
  random?: () => number;
  maxBatch?: number;
  /** safety limit of batch rounds per pass */
  maxRounds?: number;
};

export type PassResult = {
  rounds: number;
  sent: number;
  applied: number;
  conflicts: number;
  rejected: number;
  uploaded: number;
  uploadFailed: number;
  /** transport-level stop reason of the pass */
  stopped: null | "network" | "unauthorized" | "internal";
  /** client id → server id of this pass */
  idMap: Record<string, string>;
};

export async function enqueueOp(store: OfflineStore, ctx: OfflineContext, op: QueuedOpInput, clientOpId: string, now = new Date()): Promise<OutboxEntry> {
  const existing = await store.listOps(ctxKeyOf(ctx));
  const entry = createEntry(ctx, op, { clientOpId, now, existing });
  await store.putOp(entry);
  // link queued blobs to the op waiting for them
  for (const ref of entry.blobRefs) {
    const blob = await store.getBlob(ref);
    if (!blob || blob.ctxKey !== entry.ctxKey) continue;
    // a new op on a finally failed upload gets one fresh upload attempt
    const rearm = blob.status === "failed" && blob.nextAttemptAt === null ? { status: "pending" as const, lastError: null, attempts: 0 } : {};
    await store.putBlob({ ...blob, ...rearm, opClientOpId: entry.clientOpId, updatedAt: now.toISOString() });
  }
  return entry;
}

export type BlobInput = { clientId: string; workOrderId: string; kind: BlobKind; blob: Blob; preview?: Blob | null; fileName: string };

/** Stores a blob for upload; returns the reference to put into the op payload (`documentId`). */
export async function enqueueBlob(store: OfflineStore, ctx: OfflineContext, input: BlobInput, now = new Date()): Promise<string> {
  const iso = now.toISOString();
  await store.putBlob({
    clientId: input.clientId,
    ctxKey: ctxKeyOf(ctx),
    tenantId: ctx.tenantId,
    userId: ctx.userId,
    workOrderId: input.workOrderId,
    kind: input.kind,
    blob: input.blob,
    preview: input.preview ?? null,
    fileName: input.fileName,
    size: input.blob.size + (input.preview?.size ?? 0),
    status: "pending",
    documentId: null,
    attempts: 0,
    lastError: null,
    nextAttemptAt: null,
    opClientOpId: null,
    createdAt: iso,
    updatedAt: iso,
  });
  return blobRef(input.clientId);
}

const FINAL_UPLOAD_ERRORS = new Set(["invalid", "forbidden", "not_found"]);

export async function runSyncPass(deps: EngineDeps): Promise<PassResult> {
  const { store, ctx, transport, deviceId } = deps;
  const now = deps.now ?? (() => new Date());
  const random = deps.random ?? Math.random;
  const key = ctxKeyOf(ctx);
  const res: PassResult = { rounds: 0, sent: 0, applied: 0, conflicts: 0, rejected: 0, uploaded: 0, uploadFailed: 0, stopped: null, idMap: {} };

  for (const e of recoverSending(await store.listOps(key), now())) await store.putOp(e);

  const maxRounds = deps.maxRounds ?? 20;
  while (res.rounds < maxRounds) {
    const ops = await store.listOps(key);
    const blobs = await store.listBlobs(key);

    // 1. uploads before the ops that reference them
    for (const blob of selectUploads(ops, blobs, now())) {
      await store.putBlob({ ...blob, status: "uploading", updatedAt: now().toISOString() });
      const up = await transport.upload(blob);
      const iso = now().toISOString();
      if (up.ok) {
        await store.putBlob({ ...blob, status: "uploaded", documentId: up.documentId, lastError: null, nextAttemptAt: null, updatedAt: iso });
        res.uploaded++;
        continue;
      }
      const attempts = blob.attempts + 1;
      const error: OutboxError = { code: up.error === "unauthorized" || up.error === "network" ? up.error : "upload", message: up.error };
      if (FINAL_UPLOAD_ERRORS.has(up.error)) {
        await store.putBlob({ ...blob, status: "failed", attempts, lastError: error, nextAttemptAt: null, updatedAt: iso });
        res.uploadFailed++;
        // the waiting op can never be sent → rejected with a clear reason
        for (const op of ops.filter((o) => o.status === "queued" && o.blobRefs.includes(blob.clientId))) {
          await store.putOp({ ...op, status: "rejected", lastError: { code: "upload", message: up.error }, updatedAt: iso, nextAttemptAt: null });
          res.rejected++;
        }
      } else {
        await store.putBlob({ ...blob, status: "failed", attempts, lastError: error, nextAttemptAt: new Date(now().getTime() + backoffMs(attempts, random)).toISOString(), updatedAt: iso });
        if (up.error === "network" || up.error === "unauthorized") {
          res.stopped = up.error;
          return res;
        }
      }
    }

    // 2. next batch
    const current = await store.listOps(key);
    const batch = selectBatch(current, await store.listBlobs(key), now(), deps.maxBatch ?? MAX_BATCH);
    if (batch.entries.length === 0) break;
    res.rounds++;
    for (const e of batch.entries) await store.putOp({ ...e, status: "sending", updatedAt: now().toISOString() });

    const outcome = await transport.sendBatch(deviceId, batch.operations);
    if (!outcome.ok) {
      const failed = applyTransportFailure(batch.entries, { code: outcome.error === "internal" ? "internal" : outcome.error }, now(), random);
      for (const e of failed) await store.putOp(e);
      res.stopped = outcome.error;
      return res;
    }

    res.sent += batch.entries.length;
    const { changed, idMap } = applyResults(current, batch.entries, outcome.response.results, now(), random);
    Object.assign(res.idMap, idMap);
    for (const e of changed) {
      await store.putOp(e);
      if (!batch.entries.some((b) => b.clientOpId === e.clientOpId)) continue;
      if (e.status === "applied") {
        res.applied++;
        // uploaded bytes are no longer needed once the referencing op is applied
        for (const ref of e.blobRefs) await store.deleteBlob(ref);
      } else if (e.status === "conflict") res.conflicts++;
      else if (e.status === "rejected") res.rejected++;
    }
  }
  return res;
}