"""TDD — POST /repos/{repo_id}/branches/{name}/reset

Gap
---
No endpoint exists to repoint a branch head to an arbitrary (earlier) commit.
This is needed to undo the corrupt merge commit from bug #36 so the author
can re-trigger a clean merge.

Acceptance criteria
-------------------
  B1  POST reset with a known commit_id updates the branch head and returns
      the new commit_id.
  B2  POST reset with an unknown commit_id returns 404.
  B3  POST reset on an unknown branch name returns 404.
  B4  Endpoint requires valid MSign auth → 401 without headers.
  B5  POST reset on an unknown repo returns 404.
"""
from __future__ import annotations

from datetime import datetime, timezone

import pytest
from httpx import AsyncClient
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from muse.core.types import fake_id
from musehub.core.genesis import compute_branch_id
from musehub.db.musehub_repo_models import MusehubBranch, MusehubCommit, MusehubCommitRef
from musehub.types.json_types import StrDict


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------


async def _create_repo(client: AsyncClient, auth_headers: StrDict, name: str) -> str:
    resp = await client.post(
        "/api/repos",
        json={"name": name, "owner": "testuser", "initialize": False},
        headers=auth_headers,
    )
    assert resp.status_code == 201, resp.text
    return str(resp.json()["repoId"])


async def _seed_branch(
    db: AsyncSession,
    repo_id: str,
    branch_name: str,
    *,
    n_commits: int = 2,
) -> list[str]:
    """Insert n_commits in a chain on branch_name. Returns commit_ids oldest-first."""
    commit_ids: list[str] = []
    parent_ids: list[str] = []
    for i in range(n_commits):
        cid = fake_id(f"{repo_id}-{branch_name}-{i}")
        db.add(MusehubCommit(
            commit_id=cid,
            branch=branch_name,
            parent_ids=parent_ids,
            message=f"commit {i} on {branch_name}",
            author="aaronrene",
            timestamp=datetime.now(tz=timezone.utc),
        ))
        db.add(MusehubCommitRef(repo_id=repo_id, commit_id=cid))
        commit_ids.append(cid)
        parent_ids = [cid]
    db.add(MusehubBranch(
        branch_id=compute_branch_id(repo_id, branch_name),
        repo_id=repo_id,
        name=branch_name,
        head_commit_id=commit_ids[-1],
    ))
    await db.commit()
    return commit_ids


# ---------------------------------------------------------------------------
# B1 — reset moves the branch head to the target commit
# ---------------------------------------------------------------------------


@pytest.mark.asyncio
async def test_b1_reset_updates_branch_head(
    client: AsyncClient,
    auth_headers: StrDict,
    db_session: AsyncSession,
) -> None:
    """B1: POST reset with a valid commit_id updates head and returns it.

    RED: endpoint does not exist.
    GREEN: branch.head_commit_id is updated to the requested commit.
    """
    repo_id = await _create_repo(client, auth_headers, "reset-main-repo")
    commit_ids = await _seed_branch(db_session, repo_id, "main", n_commits=2)
    old_head, new_head = commit_ids[1], commit_ids[0]  # reset back one commit

    resp = await client.post(
        f"/api/repos/{repo_id}/branches/main/reset",
        json={"commitId": new_head},
        headers=auth_headers,
    )
    assert resp.status_code == 200, resp.text
    body = resp.json()
    assert body["branch"] == "main"
    assert body["commitId"] == new_head
    assert body["previousCommitId"] == old_head

    # Verify the DB row was actually updated.
    row = (await db_session.execute(
        select(MusehubBranch).where(
            MusehubBranch.repo_id == repo_id,
            MusehubBranch.name == "main",
        )
    )).scalar_one()
    assert row.head_commit_id == new_head


# ---------------------------------------------------------------------------
# B2 — reset to an unknown commit_id returns 404
# ---------------------------------------------------------------------------


@pytest.mark.asyncio
async def test_b2_reset_unknown_commit_returns_404(
    client: AsyncClient,
    auth_headers: StrDict,
    db_session: AsyncSession,
) -> None:
    """B2: POST reset with a commit_id not in the store returns 404."""
    repo_id = await _create_repo(client, auth_headers, "reset-bad-commit-repo")
    await _seed_branch(db_session, repo_id, "main")

    resp = await client.post(
        f"/api/repos/{repo_id}/branches/main/reset",
        json={"commitId": fake_id("ghost-commit")},
        headers=auth_headers,
    )
    assert resp.status_code == 404, resp.text


# ---------------------------------------------------------------------------
# B3 — reset on an unknown branch name returns 404
# ---------------------------------------------------------------------------


@pytest.mark.asyncio
async def test_b3_reset_unknown_branch_returns_404(
    client: AsyncClient,
    auth_headers: StrDict,
    db_session: AsyncSession,
) -> None:
    """B3: POST reset on a branch that doesn't exist returns 404."""
    repo_id = await _create_repo(client, auth_headers, "reset-no-branch-repo")
    commit_ids = await _seed_branch(db_session, repo_id, "main")

    resp = await client.post(
        f"/api/repos/{repo_id}/branches/nonexistent/reset",
        json={"commitId": commit_ids[0]},
        headers=auth_headers,
    )
    assert resp.status_code == 404, resp.text


# ---------------------------------------------------------------------------
# B4 — auth required
# ---------------------------------------------------------------------------


@pytest.mark.asyncio
async def test_b4_reset_requires_auth(client: AsyncClient) -> None:
    """B4: POST reset without auth returns 401."""
    resp = await client.post(
        f"/api/repos/{fake_id('r')}/branches/main/reset",
        json={"commitId": fake_id("c")},
    )
    assert resp.status_code == 401


# ---------------------------------------------------------------------------
# B5 — unknown repo returns 404
# ---------------------------------------------------------------------------


@pytest.mark.asyncio
async def test_b5_reset_unknown_repo_returns_404(
    client: AsyncClient,
    auth_headers: StrDict,
) -> None:
    """B5: POST reset on an unknown repo_id returns 404."""
    resp = await client.post(
        f"/api/repos/{fake_id('ghost-repo')}/branches/main/reset",
        json={"commitId": fake_id("c")},
        headers=auth_headers,
    )
    assert resp.status_code == 404, resp.text