import { inject, injectable } from "@codemation/core";
import type { AppConfig } from "../presentation/config/AppConfig";
import { ApplicationTokens } from "../applicationTokens";
import type { ProcessRunner } from "../process/ProcessRunner.types";

@injectable()
export class ServedCommitShaReader {
  private cached: Promise<string | null> | undefined;

  constructor(
    @inject(ApplicationTokens.AppConfig) private readonly appConfig: AppConfig,
    @inject(ApplicationTokens.ProcessRunner) private readonly processRunner: ProcessRunner,
  ) {}

  async read(): Promise<string | null> {
    this.cached ??= this.resolveSha();
    return this.cached;
  }

  private resolveSha(): Promise<string | null> {
    const fromEnv = this.appConfig.env.CODEMATION_COMMIT_SHA?.trim();
    if (fromEnv) {
      return Promise.resolve(fromEnv);
    }
    return this.readFromGit();
  }

  private readFromGit(): Promise<string | null> {
    let child;
    try {
      child = this.processRunner.spawn("git", ["rev-parse", "HEAD"], {
        cwd: this.appConfig.consumerRoot,
        stdio: ["ignore", "pipe", "pipe"],
      });
    } catch {
      return Promise.resolve(null);
    }

    return new Promise<string | null>((resolve) => {
      let stdout = "";
      child.stdout?.on("data", (chunk: Buffer | string) => {
        stdout += chunk.toString();
      });
      child.once("error", () => {
        resolve(null);
      });
      child.once("close", (exitCode) => {
        if (exitCode === 0) {
          resolve(stdout.trim() || null);
        } else {
          resolve(null);
        }
      });
    });
  }
}