import { XrpcRequestError } from './bobbin.ts';
import type { Getter } from './reads.ts';

export interface DefaultBranch {
  name: string;
  hash: string;
  when: string;
}

export interface TreeFile {
  name: string;
  mode: string;
  size: number;
}

export interface TreeResponse {
  ref: string;
  files: TreeFile[];
}

export interface BlobResponse {
  content: string;
  encoding: 'utf-8' | 'base64';
  size: number;
  isBinary?: boolean;
}

export function createGit(pool: Getter, repoUri: string) {
  return {
    getDefaultBranch(): Promise<DefaultBranch> {
      return pool.get<DefaultBranch>('sh.tangled.repo.getDefaultBranch', { repo: repoUri });
    },
    listTree(ref: string): Promise<TreeResponse> {
      return pool.get<TreeResponse>('sh.tangled.repo.tree', { repo: repoUri, ref });
    },
    async getBlob(ref: string, path: string): Promise<string | null> {
      let data: BlobResponse;
      try {
        data = await pool.get<BlobResponse>('sh.tangled.repo.blob', { repo: repoUri, ref, path });
      } catch (err) {
        // A 4xx means the path/ref doesn't exist — treat as absent. Anything
        // else (pool exhaustion, 5xx) is a real failure and propagates.
        if (err instanceof XrpcRequestError) return null;
        throw err;
      }
      if (data.isBinary) return null;
      return data.encoding === 'base64' ? decodeBase64Utf8(data.content) : data.content;
    },
  };
}

/** Decode base64 as UTF-8 (atob alone yields Latin-1, mangling non-ASCII text). */
function decodeBase64Utf8(b64: string): string {
  const bin = atob(b64);
  const bytes = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) bytes[i] = bin.charCodeAt(i);
  return new TextDecoder().decode(bytes);
}

export type Git = ReturnType<typeof createGit>;