import { Error2, ErrorCodes } from '#/errors';

import type { GithubRef } from './source';
import type { PluginGithubRef } from './types';

export interface GithubSourceInput {
  readonly kind: 'github';
  readonly owner: string;
  readonly repo: string;
  readonly ref?: GithubRef;
}

export interface GithubSourceResolution {
  readonly tarballUrl: string;
  readonly displayVersion: string;
  readonly ref: PluginGithubRef;
}

export async function resolveGithubCommitSha(
  owner: string,
  repo: string,
  ref: string,
): Promise<string> {
  const encodedRef = encodeCodeloadRefPath(ref);
  const url = `https://github.com/${owner}/${repo}/commits/${encodedRef}.atom`;
  const resp = await fetch(url, {
    headers: { accept: 'application/atom+xml', range: 'bytes=0-4095' },
    signal: AbortSignal.timeout(10_000),
  });
  if (!resp.ok) {
    throw new Error2(
      ErrorCodes.PLUGIN_LOAD_FAILED,
      `Could not resolve ${owner}/${repo}@${ref}: HTTP ${resp.status} ${resp.statusText}.`,
      { details: { owner, repo, ref, status: resp.status } },
    );
  }
  const feed = await resp.text();
  const sha = /Grit::Commit\/([0-9a-f]{40})/i.exec(feed)?.[1];
  if (sha === undefined) {
    throw new Error2(
      ErrorCodes.PLUGIN_LOAD_FAILED,
      `Could not resolve ${owner}/${repo}@${ref} to a commit SHA.`,
      { details: { owner, repo, ref } },
    );
  }
  return sha.toLowerCase();
}

export async function resolveGithubSource(
  input: GithubSourceInput,
): Promise<GithubSourceResolution> {
  const { owner, repo } = input;

  if (input.ref !== undefined) {
    return {
      tarballUrl: codeloadUrl(owner, repo, input.ref),
      displayVersion: input.ref.value,
      ref: { kind: input.ref.kind, value: input.ref.value },
    };
  }

  const latestTag = await tryResolveLatestReleaseTag(owner, repo);
  if (latestTag !== undefined) {
    return {
      tarballUrl: codeloadUrl(owner, repo, { kind: 'tag', value: latestTag }),
      displayVersion: latestTag,
      ref: { kind: 'tag', value: latestTag },
    };
  }

  const headProbe = await fetch(`https://codeload.github.com/${owner}/${repo}/zip/HEAD`, {
    method: 'HEAD',
    signal: AbortSignal.timeout(10_000),
  });
  if (headProbe.status === 404) {
    throw new Error2(
      ErrorCodes.PLUGIN_LOAD_FAILED,
      `Repository \`${owner}/${repo}\` not found or not accessible.`,
      { details: { owner, repo } },
    );
  }
  if (!headProbe.ok) {
    throw new Error2(
      ErrorCodes.PLUGIN_LOAD_FAILED,
      `Could not access \`${owner}/${repo}\`: HTTP ${headProbe.status} ${headProbe.statusText}.`,
      { details: { owner, repo, status: headProbe.status } },
    );
  }
  return {
    tarballUrl: `https://codeload.github.com/${owner}/${repo}/zip/HEAD`,
    displayVersion: 'HEAD',
    ref: { kind: 'branch', value: 'HEAD' },
  };
}

async function tryResolveLatestReleaseTag(owner: string, repo: string): Promise<string | undefined> {
  const url = `https://github.com/${owner}/${repo}/releases/latest`;
  const resp = await fetch(url, {
    redirect: 'manual',
    signal: AbortSignal.timeout(10_000),
  });

  if (resp.status === 404) return undefined;

  if (resp.status !== 301 && resp.status !== 302) {
    throw new Error2(
      ErrorCodes.PLUGIN_LOAD_FAILED,
      `Could not look up latest release of \`${owner}/${repo}\`: ` +
        `HTTP ${resp.status} ${resp.statusText} (${url}). ` +
        `Pin a specific ref with \`/tree/<branch|tag|sha>\` to bypass release lookup.`,
      { details: { owner, repo, status: resp.status, url } },
    );
  }

  const location = resp.headers.get('location');
  if (location === null) return undefined;

  const match = /\/releases\/tag\/([^/?#]+)/.exec(location);
  if (match === null) return undefined;
  try {
    return decodeURIComponent(match[1]!);
  } catch {
    return match[1];
  }
}

function codeloadUrl(owner: string, repo: string, ref: GithubRef): string {
  const base = `https://codeload.github.com/${owner}/${repo}/zip`;
  const encoded = encodeCodeloadRefPath(ref.value);
  if (ref.kind === 'sha') return `${base}/${encoded}`;
  if (ref.kind === 'tag') return `${base}/refs/tags/${encoded}`;
  return `${base}/${encoded}`;
}

function encodeCodeloadRefPath(value: string): string {
  return value.split('/').map(encodeURIComponent).join('/');
}