// What the forge's holder does for a delivery (novox/hq ADR 0239): the commit's note under
// refs/notes/mesh-plan, the delivery's view on its pull request, and its statuses — asked by mesh-delivery,
// the delivery's owner, through this module's tools. The forge is this module's; mesh-delivery never writes
// to it itself.
//
// **The note is written in the forge's own repository, as the forge's own user.** The forge's API reads a
// note and writes none, and a push needs a clone and a credential nobody else should hold; the forge's
// container holds the bare repository and git. So the line is appended there, by `git notes append`, as the
// account the forge runs as — the mesh's own forge, never a person's or an agent's hand. Appending is
// idempotent here: a line the note already has is not added again, so asking twice adds nothing.
//
// Pure functions and an injectable runner, so this is tested without a forge.

import { execFile } from "node:child_process";
import { promisify } from "node:util";
import type { ToolDefinition } from "@novox/mesh-sdk/tools";
import type { CommitStatus } from "./client.js";
import { checkName } from "./guard.js";

/** How a command is run: docker on the forge's machine, or a test's. */
export type Runner = (file: string, args: string[]) => Promise<{ stdout: string; code: number }>;

const execFileP = promisify(execFile);

export const run: Runner = async (file, args) => {
  try {
    const { stdout } = await execFileP(file, args, { maxBuffer: 4 << 20 });
    return { stdout, code: 0 };
  } catch (err) {
    const e = err as { code?: number; stdout?: string };
    return { stdout: e.stdout ?? "", code: typeof e.code === "number" ? e.code : 1 };
  }
};

const name = /^[A-Za-z0-9_.-]+$/;
const sha = /^[0-9a-fA-F]{7,64}$/;
const ref = /^[a-z0-9][a-z0-9-]*$/;

/** A note line as it may be written: one line, bounded, nothing that is not text. */
export function noteLine(line: string): string {
  const one = String(line ?? "").replace(/[\r\n\t]+/g, " ").replace(/\s+/g, " ").trim();
  if (!one) throw new Error("an empty line is no note");
  return one.length > 2000 ? one.slice(0, 1999) + "…" : one;
}

/** Where the forge keeps a repository, inside its container. */
export function gitDir(owner: string, repo: string): string {
  if (!name.test(owner) || !name.test(repo)) throw new Error(`${owner}/${repo} is not a repository's name`);
  return `/data/git/repositories/${owner.toLowerCase()}/${repo.toLowerCase()}.git`;
}

/** The commands the note is read and appended with, in the forge's container, as its user. */
export function noteArgs(container: string, owner: string, repo: string, commit: string, notesRef: string, line?: string): string[] {
  if (!name.test(container)) throw new Error(`${container} is not a container's name`);
  if (!sha.test(commit)) throw new Error(`${commit} is not a commit`);
  if (!ref.test(notesRef)) throw new Error(`${notesRef} is not a notes ref`);
  const base = ["exec", "-u", "git", container, "git", "--git-dir", gitDir(owner, repo),
    "-c", "user.name=mesh", "-c", "user.email=mesh@mesh.invalid", "notes", `--ref=${notesRef}`];
  return line === undefined ? [...base, "show", commit] : [...base, "append", "-m", noteLine(line), commit];
}

/** Append a line to a commit's note, unless the note already holds it. Answers whether it was added. */
export async function appendNote(runner: Runner, container: string, owner: string, repo: string, commit: string,
  notesRef: string, line: string): Promise<{ added: boolean; lines: number }> {
  const wanted = noteLine(line);
  const shown = await runner("docker", noteArgs(container, owner, repo, commit, notesRef));
  // No note yet is git's exit 1 with nothing on stdout; anything else unreadable is said.
  const lines = shown.code === 0 ? shown.stdout.split("\n").filter((l) => l.trim() !== "") : [];
  if (lines.includes(wanted)) return { added: false, lines: lines.length };
  const appended = await runner("docker", noteArgs(container, owner, repo, commit, notesRef, wanted));
  if (appended.code !== 0) throw new Error(`the note on ${commit.slice(0, 8)} could not be appended (git exited ${appended.code})`);
  return { added: true, lines: lines.length + 1 };
}

/** The marker that makes one comment of a pull request the delivery's view. */
export const VIEW_MARKER = "<!-- mesh-delivery:view -->";

/** The view's body, marked: mesh-delivery writes it, this keeps exactly one of them per pull request. */
export function viewBody(body: string): string {
  const b = String(body ?? "");
  return b.includes(VIEW_MARKER) ? b : `${VIEW_MARKER}\n${b}`;
}

/** Which comment is the view: the first that carries the marker, or none yet. */
export function viewComment<T extends { id: number; body: string }>(comments: T[]): T | undefined {
  return comments.find((c) => c.body.includes(VIEW_MARKER));
}

const states = new Set(["pending", "success", "error", "failure", "warning"]);

/** The merge check's contexts (pulls.ts): a branch's protection may require them. */
const mergeCheckContexts = new Set(["mesh/merge-gate", "mesh/repo-check"]);

/** A status mesh-delivery asks for, checked: one of the forge's states, a context of the mesh's own, a
 *  bounded description. */
export function deliveryStatus(context: string, state: string, description: string, target?: string) {
  if (!/^mesh\/[a-z-]+$/.test(context)) throw new Error(`${context} is not a status of the mesh's own`);
  if (!states.has(state)) throw new Error(`${state} is not a status the forge keeps`);
  // The merge check's statuses are its verdict's, set when the controller says it, and a branch may require
  // them: never set to a verdict by hand, so nothing passes — or fails — a merge past the check (novox/hq
  // issue 293). Pending is no verdict: it is what this holder says on every new head until the verdict comes,
  // and what a recheck of the same head says, so the old verdict does not let it merge while the fresh check
  // runs.
  if (mergeCheckContexts.has(context) && state !== "pending") {
    throw new Error(`${context} is the merge check's status, set by its verdict only (pending, for a check asked again, is the one state it takes by hand)`);
  }
  let d = String(description ?? "").replace(/\s+/g, " ").trim();
  if (d.length > 140) d = d.slice(0, 139) + "…";
  return { state: state as "pending" | "success" | "error" | "failure" | "warning", context, description: d,
    ...(target && /^https?:\/\//.test(target) ? { target_url: target } : {}) };
}

/** What the status tool writes with: the forge, and the gate writer the merge check's statuses go through. */
export interface StatusWriters {
  setCommitStatus(owner: string, repo: string, sha: string, status: CommitStatus): Promise<void>;
  gates: { rechecked(owner: string, repo: string, sha: string, status: CommitStatus): Promise<void> };
}

/**
 * The `gitea_commit_status` tool. **The merge check's pending goes through the module's one writer** (novox/hq issue
 * 456): a recheck's pending on mesh/merge-gate or mesh/repo-check takes its turn on the head's chain (gate.ts), so an
 * old run's verdict in flight lands before it and a redelivered one is dropped. Served from the watcher's bundle
 * (index.ts), the process that holds that writer: each bundle the runtime serves is its own process. The mesh's other
 * statuses (mesh/delivery, mesh/delivery-group) are written as they were.
 */
export function commitStatusTool(writers: StatusWriters): ToolDefinition {
  return {
    name: "gitea_commit_status",
    description: "Set one of the mesh's statuses on a commit (mesh/delivery, mesh/delivery-group): pending, success, error, failure or warning, a short description, and the page it links to. The merge check's statuses (mesh/merge-gate, mesh/repo-check) take pending only — a recheck putting them back until the fresh verdict sets them — on the head's whole sha, in their turn after the check's earlier writes.",
    input: {
      owner: { type: "string", description: "the repository owner" },
      repo: { type: "string", description: "the repository name" },
      sha: { type: "string", description: "the commit" },
      context: { type: "string", description: "the status's name, mesh/…" },
      state: { type: "string", description: "pending | success | error | failure | warning" },
      description: { type: "string", description: "one line" },
      target_url: { type: "string", description: "the page it links to (the pull request)" },
    },
    run: async (args) => {
      const owner = checkName("owner", args.owner), repo = checkName("name", args.repo), sha = String(args.sha ?? "");
      const status = deliveryStatus(String(args.context), String(args.state), String(args.description ?? ""),
        args.target_url ? String(args.target_url) : undefined);
      if (mergeCheckContexts.has(status.context)) {
        // The writer keeps a head by its whole sha, as the forge announced it: a short one would be another head.
        if (!/^([0-9a-f]{40}|[0-9a-f]{64})$/i.test(sha)) {
          throw new Error(`${JSON.stringify(args.sha)} is not a head's whole sha: the merge check's status names the head whole. Nothing was sent`);
        }
        await writers.gates.rechecked(owner, repo, sha, status);
      } else {
        await writers.setCommitStatus(owner, repo, sha, status);
      }
      return { set: status };
    },
  };
}