from __future__ import annotations

from typing import Any
from unittest.mock import patch

import subprocess

from ai_reviewer.diff import run_git_diff


def _completed(cmd: list[str], returncode: int, stdout: str = "", stderr: str = "") -> subprocess.CompletedProcess[Any]:
    return subprocess.CompletedProcess(cmd, returncode, stdout, stderr)


def test_run_git_diff_prefers_direct_refs():
    calls: list[list[str]] = []

    def fake_run(cmd, check=False, capture_output=False, text=False):  # type: ignore[override]
        calls.append(cmd)
        if cmd[3] == "diff":
            if cmd[4] == "base...head":
                return _completed(cmd, 0, stdout="ok")
            return _completed(cmd, 128, stderr="fatal")
        raise AssertionError("fetch should not run when refs exist locally")

    with patch("ai_reviewer.diff.subprocess.run", side_effect=fake_run):
        output = run_git_diff(".", "base", "head")

    assert output == "ok"
    # Only one diff attempt should be needed when local refs exist.
    assert len(calls) == 1


def test_run_git_diff_falls_back_to_origin_refs_after_fetch():
    fetched = False
    diff_attempts: list[str] = []

    def fake_run(cmd, check=False, capture_output=False, text=False):  # type: ignore[override]
        nonlocal fetched
        if cmd[3] == "diff":
            diff_attempts.append(cmd[4])
            spec = cmd[4]
            if spec == "origin/base...origin/head" and fetched:
                return _completed(cmd, 0, stdout="remote-ok")
            return _completed(cmd, 128, stderr="missing ref")
        if cmd[3] == "fetch":
            fetched = True
            return _completed(cmd, 0)
        raise AssertionError("unexpected git invocation")

    with patch("ai_reviewer.diff.subprocess.run", side_effect=fake_run):
        output = run_git_diff(".", "base", "head")

    assert output == "remote-ok"
    assert "origin/base...origin/head" in diff_attempts
    # Ensure the fallback only succeeds after fetch.
    assert diff_attempts.index("origin/base...origin/head") > diff_attempts.index("base...head")