import { getCommit, git, listTree, readBlob, revParse } from "./git";
import type { RepoRecord } from "./repos";
import { createRun, type Run, type RunEvent } from "./runs";
import { isWorkflowFile, matchesFilter, matchesPaths, parseWorkflow, WORKFLOW_DIR, WorkflowError, type Workflow } from "./workflows";

// Starting workflow runs: on pushes (over SSH, HTTPS or from the web editor), by hand, and again.
// Like lib/git.ts this is used by the SSH server, so it must not import anything from next/*.

export class CiError extends Error {}

type WorkflowFile = { path: string; workflow: Workflow } | { path: string; error: string; name: string };

/** The workflow files at a commit, parsed; files that don't parse carry their error instead. */
export async function readWorkflows(dir: string, sha: string): Promise<WorkflowFile[]> {
  const entries = await listTree(dir, sha, WORKFLOW_DIR).catch(() => []);
  const files: WorkflowFile[] = [];
  for (const entry of entries) {
    if (entry.type !== "blob" || !isWorkflowFile(entry.name)) continue;
    files.push(await readWorkflow(dir, sha, entry.path));
  }
  return files;
}

async function readWorkflow(dir: string, sha: string, path: string): Promise<WorkflowFile> {
  const name = path.split("/").pop()!.replace(/\.ya?ml$/i, "");
  const blob = await readBlob(dir, sha, path).catch(() => null);
  if (!blob) return { path, name, error: `${path} doesn't exist at this commit.` };
  if (blob.tooLarge || blob.binary) return { path, name, error: "The workflow file is too large or not text." };
  try {
    return { path, workflow: parseWorkflow(blob.content.toString("utf8"), path) };
  } catch (e) {
    if (e instanceof WorkflowError) return { path, name, error: e.message };
    throw e;
  }
}

async function start(repo: RepoRecord, file: WorkflowFile, run: { event: RunEvent; ref: string; sha: string; actorId: string | null }) {
  const commit = await getCommit(repo.dir, run.sha);
  return createRun({
    repoId: repo.id,
    workflowPath: file.path,
    workflowName: "workflow" in file ? file.workflow.name : file.name,
    ...run,
    title: commit?.subject || run.sha.slice(0, 7),
    jobs: "workflow" in file ? file.workflow.jobs : { error: file.error },
  });
}

/** Files changed between two commits, or null when that isn't known (a new branch). */
async function changedFiles(dir: string, before: string | null, after: string) {
  if (!before) return null;
  const out = await git(dir, ["diff", "--name-only", "-z", before, after]).catch(() => null);
  return out === null ? null : out.split("\0").filter(Boolean);
}

/** Starts the workflows that run on a push of `ref` (refs/heads/… or refs/tags/…). */
async function onPush(repo: RepoRecord, ref: string, before: string | null, after: string, actorId: string | null) {
  const sha = await revParse(repo.dir, after);
  if (!sha) return;
  const tag = ref.startsWith("refs/tags/");
  const name = ref.replace(/^refs\/(heads|tags)\//, "");
  let changed: string[] | null | undefined;

  for (const file of await readWorkflows(repo.dir, sha)) {
    // A broken file can't say when it runs, so it fails on every push, where its author will see it.
    if ("workflow" in file) {
      const push = file.workflow.push;
      if (!push || !matchesFilter(tag ? push.tags : push.branches, name)) continue;
      if (!tag) {
        changed ??= await changedFiles(repo.dir, before, sha);
        if (!matchesPaths(push.paths, changed)) continue;
      }
    }
    await start(repo, file, { event: "push", ref, sha, actorId });
  }
}

/** Starts workflows for whatever a push changed, given the refs before and after it. */
export async function onRefsUpdated(repo: RepoRecord, before: Map<string, string>, after: Map<string, string>, actorId: string | null) {
  for (const [ref, sha] of after) {
    const old = before.get(ref) ?? null;
    if (old === sha) continue;
    await onPush(repo, ref, old, sha, actorId);
  }
}

/** For callers that shouldn't wait on (or fail because of) workflows starting. */
export function startWorkflowsInBackground(work: Promise<unknown>) {
  work.catch((e) => console.error("[ci] could not start workflows:", e));
}

/** Starts a workflow by hand on a branch, if it has `on: workflow_dispatch`. Returns the run number. */
export async function dispatchWorkflow(repo: RepoRecord, path: string, branch: string, actorId: string) {
  const sha = await revParse(repo.dir, `refs/heads/${branch}`);
  if (!sha) throw new CiError(`There is no branch named ${branch}.`);
  const file = await readWorkflow(repo.dir, sha, path);
  if ("error" in file) throw new CiError(file.error);
  if (!file.workflow.dispatch) throw new CiError("This workflow can't be run by hand. Add workflow_dispatch to its on: triggers.");
  return start(repo, file, { event: "workflow_dispatch", ref: `refs/heads/${branch}`, sha, actorId });
}

/** Runs a run's workflow again, as it was at the run's commit. Returns the new run's number. */
export async function rerunWorkflow(repo: RepoRecord, run: Run, actorId: string) {
  const file = await readWorkflow(repo.dir, run.sha, run.workflowPath);
  return start(repo, file, { event: run.event, ref: run.ref, sha: run.sha, actorId });
}