"""muse#54 item 7 -- `muse reflog diff @{N} @{M}` as a first-class point-in-time
comparison, resolving both specs from the same branch's reflog automatically
instead of requiring manual `muse diff "branch@{N}" "branch@{M}"` construction.
"""
from __future__ import annotations

import datetime
import json
import pathlib

from tests.cli_test_helper import CliRunner
from muse.core.types import fake_id, Manifest
from muse.core.paths import ref_path, muse_dir

cli = None
runner = CliRunner()


def _env(root: pathlib.Path) -> Manifest:
    return {"MUSE_REPO_ROOT": str(root)}


def _run(root: pathlib.Path, *args: str):
    return runner.invoke(cli, list(args), env=_env(root))


def _init_repo(tmp_path: pathlib.Path) -> tuple[pathlib.Path, str]:
    dot_muse = muse_dir(tmp_path)
    dot_muse.mkdir()
    repo_id = fake_id("repo")
    (dot_muse / "repo.json").write_text(json.dumps({
        "repo_id": repo_id, "domain": "code", "default_branch": "main",
        "created_at": "2025-01-01T00:00:00+00:00",
    }), encoding="utf-8")
    (dot_muse / "HEAD").write_text("ref: refs/heads/main\n", encoding="utf-8")
    (dot_muse / "refs" / "heads").mkdir(parents=True)
    (dot_muse / "snapshots").mkdir()
    (dot_muse / "commits").mkdir()
    (dot_muse / "objects").mkdir()
    return tmp_path, repo_id


def _commit_file(root: pathlib.Path, content: str, message: str) -> str:
    (root / "f.txt").write_text(content)
    add = _run(root, "code", "add", "f.txt")
    assert add.exit_code == 0, add.output
    commit = _run(root, "commit", "-m", message, "--json")
    assert commit.exit_code == 0, commit.output
    return json.loads(commit.output)["commit_id"]


class TestReflogDiff:
    def test_diff_two_head_indices(self, tmp_path: pathlib.Path) -> None:
        root, repo_id = _init_repo(tmp_path)
        _commit_file(root, "v1\n", "c1")
        _commit_file(root, "v2\n", "c2")
        _commit_file(root, "v3\n", "c3")

        # @{2} is c1 (oldest of the three), @{0} is c3 (newest/current HEAD).
        result = _run(root, "reflog", "diff", "2", "0", "--json")
        assert result.exit_code == 0, result.output
        data = json.loads(result.output)
        assert data["from_ref"] == "@{2}"
        assert data["to_ref"] == "@{0}"
        assert data["has_changes"] is True

    def test_diff_defaults_second_index_to_zero(self, tmp_path: pathlib.Path) -> None:
        root, repo_id = _init_repo(tmp_path)
        _commit_file(root, "v1\n", "c1")
        _commit_file(root, "v2\n", "c2")

        result = _run(root, "reflog", "diff", "1", "--json")
        assert result.exit_code == 0, result.output
        data = json.loads(result.output)
        assert data["to_ref"] == "@{0}"

    def test_diff_with_branch_flag(self, tmp_path: pathlib.Path) -> None:
        root, repo_id = _init_repo(tmp_path)
        _commit_file(root, "v1\n", "c1")
        _commit_file(root, "v2\n", "c2")

        result = _run(root, "reflog", "diff", "1", "0", "--branch", "main", "--json")
        assert result.exit_code == 0, result.output
        data = json.loads(result.output)
        assert data["from_ref"] == "main@{1}"
        assert data["to_ref"] == "main@{0}"

    def test_diff_identical_indices_has_no_changes(self, tmp_path: pathlib.Path) -> None:
        root, repo_id = _init_repo(tmp_path)
        _commit_file(root, "v1\n", "c1")

        result = _run(root, "reflog", "diff", "0", "0", "--json")
        assert result.exit_code == 0, result.output
        data = json.loads(result.output)
        assert data["has_changes"] is False

    def test_diff_out_of_range_index_errors(self, tmp_path: pathlib.Path) -> None:
        root, repo_id = _init_repo(tmp_path)
        _commit_file(root, "v1\n", "c1")

        result = _run(root, "reflog", "diff", "99", "0", "--json")
        assert result.exit_code == 1