/**
 * Per-repository broker-root resolution for the file watcher.
 *
 * The c2c CLI resolves this itself for every command. Pi needs the same
 * answer independently because `fs.watch` attaches directly to the inbox
 * directory, rather than going through the CLI.
 */

import { execFileSync } from "node:child_process";
import { createHash } from "node:crypto";
import * as path from "node:path";

export type BrokerRootSource = "override" | "c2c-state-home" | "home";

export interface PerRepoBrokerRoot {
  root: string;
  fingerprint: string;
  source: BrokerRootSource;
}

function gitOutput(cwd: string, args: string[]): string | undefined {
  try {
    const output = execFileSync("git", ["-C", cwd, ...args], {
      encoding: "utf8",
      stdio: ["ignore", "pipe", "ignore"],
    }).trim();
    return output || undefined;
  } catch {
    return undefined;
  }
}

/** Match c2c's fingerprint input: origin URL, then repository top-level. */
export function resolveRepoFingerprint(cwd: string): string {
  const identity = gitOutput(cwd, ["config", "--get", "remote.origin.url"])
    ?? gitOutput(cwd, ["rev-parse", "--show-toplevel"])
    ?? cwd;
  return createHash("sha256").update(identity).digest("hex");
}

/**
 * Match c2c's per-repository precedence for direct inbox watching. Generic
 * XDG_STATE_HOME is deliberately ignored because harnesses can repurpose it
 * per profile and thereby split the machine-wide broker.
 */
export function resolvePerRepoBrokerRoot(
  cwd: string,
  env: NodeJS.ProcessEnv = process.env,
): PerRepoBrokerRoot {
  const fingerprint = resolveRepoFingerprint(cwd);
  const explicit = (env.C2C_MCP_BROKER_ROOT ?? "").trim();
  if (explicit) return { root: explicit, fingerprint, source: "override" };

  const stateHome = (env.C2C_STATE_HOME ?? "").trim();
  if (stateHome) {
    return {
      root: path.join(stateHome, "c2c", "repos", fingerprint, "broker"),
      fingerprint,
      source: "c2c-state-home",
    };
  }

  const home = (env.HOME ?? "").trim() || ".";
  return {
    root: path.join(home, ".c2c", "repos", fingerprint, "broker"),
    fingerprint,
    source: "home",
  };
}