import { repoDb } from "./scoped-db";
import { badRequest, conflict, forbidden } from "./errors";
import { branchSha, listRefs } from "./git/refs";
import { kickBranch } from "./merge-automation";
import { dequeuePull, enqueuePull } from "./merge-queue";
import { afterPullChange } from "./pull-events";
import { stackParent } from "./stacks";
import { addIssueEvent, MergeError } from "./pulls";
import type { MergeMethod, Viewer } from "~/lib/types";
import type { PullAccess } from "./reviews-write";

function rethrowMerge(error: unknown): never {
  if (error instanceof MergeError) throw conflict(error.message);
  throw error;
}

/** Requires write access. Enabling pins the current head; a missing or stale `expectedHead` is a 409. */
export async function setAutoMerge(
  access: PullAccess,
  viewer: Viewer,
  input: { enabled: boolean; method: MergeMethod; message: string; expectedHead?: string },
): Promise<void> {
  const { pull } = access;
  if (!input.enabled) {
    await repoDb(pull.repo_id).run("DELETE FROM pull_auto_merges WHERE issue_id = ?", pull.issue_id);
    await addIssueEvent(pull, viewer.id, "auto_merge_disabled", {});
    return;
  }
  if (pull.state !== "open") throw badRequest("Pull request is not open");
  if (pull.head_sha !== input.expectedHead) throw conflict("The head branch changed; reload and try again");
  await repoDb(pull.repo_id).run(
    `INSERT INTO pull_auto_merges (issue_id, repo_id, method, message, enabled_by, created_at, head_sha)
     VALUES (?, ?, ?, ?, ?, ?, ?)
     ON CONFLICT (issue_id) DO UPDATE SET method = excluded.method, message = excluded.message,
       enabled_by = excluded.enabled_by, head_sha = excluded.head_sha`,
    pull.issue_id,
    pull.repo_id,
    input.method,
    input.message,
    viewer.id,
    Date.now(),
    pull.head_sha,
  );
  await addIssueEvent(pull, viewer.id, "auto_merge_enabled", { method: input.method });
  await kickBranch(pull.repo_id, pull.base_ref);
}

/** Requires write access. Queueing pins the current head; a missing or stale `expectedHead` is a 409. */
export async function setMergeQueue(
  access: PullAccess,
  viewer: Viewer,
  input: { queued: boolean; method: "merge" | "squash"; expectedHead?: string },
): Promise<void> {
  const { pull } = access;
  if (input.queued) {
    if (pull.state !== "open" || pull.draft === 1) throw badRequest("Only open, ready pull requests can be queued");
    if (pull.head_sha !== input.expectedHead) throw conflict("The head branch changed; reload and try again");
    const parent = await stackParent(pull);
    if (parent) throw badRequest(`This pull request is stacked on #${parent.number}; merge the stack instead`);
    await enqueuePull(pull, input.method, viewer).catch(rethrowMerge);
  } else {
    await dequeuePull(pull, viewer.id, null);
  }
}

/** Requires read access; only the author or a collaborator may change base or draft state. */
export async function updatePull(
  access: PullAccess,
  viewer: Viewer,
  input: { base?: string; draft?: boolean },
): Promise<void> {
  const { repo, permission, pull } = access;
  if (pull.author_id !== viewer.id && permission === "read") throw forbidden();
  if (input.base && input.base !== pull.base_ref) {
    const sha = branchSha(await listRefs(repo), input.base);
    if (!sha) throw badRequest("Base branch not found");
    await repoDb(pull.repo_id).run(
      `UPDATE pull_requests SET base_ref = ?, base_sha = ?, mergeable = 'unknown', stacked_on_issue_id = NULL,
         restack_upstream_sha = NULL WHERE issue_id = ?`,
      input.base,
      sha,
      pull.issue_id,
    );
    await addIssueEvent(pull, viewer.id, "base_changed", { from: pull.base_ref, to: input.base });
  }
  if (input.draft !== undefined && input.draft !== (pull.draft === 1)) {
    await repoDb(pull.repo_id).run(
      "UPDATE pull_requests SET draft = ? WHERE issue_id = ?",
      input.draft ? 1 : 0,
      pull.issue_id,
    );
    await addIssueEvent(pull, viewer.id, input.draft ? "converted_to_draft" : "ready_for_review", {});
    if (!input.draft) afterPullChange(pull, "ready_for_review", viewer, pull.head_sha);
  }
}