//! Tests for the typed pipeline state machine.
use super::*;
use std::num::NonZeroU32;

fn nz(n: u32) -> NonZeroU32 {
    NonZeroU32::new(n).unwrap()
}
fn fb(name: &str) -> BranchName {
    BranchName(name.to_string())
}
fn sha(s: &str) -> GitSha {
    GitSha(s.to_string())
}
fn sid(s: &str) -> StoryId {
    StoryId(s.to_string())
}

#[test]
fn happy_path_backlog_through_archived() {
    let s = Stage::Backlog;
    let s = transition(s, PipelineEvent::DepsMet).unwrap();
    assert!(matches!(s, Stage::Coding));

    let s = transition(
        s,
        PipelineEvent::QaSkipped {
            feature_branch: fb("feature/story-1"),
            commits_ahead: nz(3),
        },
    )
    .unwrap();
    assert!(matches!(s, Stage::Merge { .. }));

    let s = transition(
        s,
        PipelineEvent::MergeSucceeded {
            merge_commit: sha("abc123"),
        },
    )
    .unwrap();
    assert!(matches!(s, Stage::Done { .. }));

    let s = transition(s, PipelineEvent::Accepted).unwrap();
    assert!(matches!(
        s,
        Stage::Archived {
            reason: ArchiveReason::Completed,
            ..
        }
    ));
}

#[test]
fn happy_path_with_qa() {
    let s = Stage::Coding;
    let s = transition(s, PipelineEvent::GatesStarted).unwrap();
    assert!(matches!(s, Stage::Qa));

    let s = transition(
        s,
        PipelineEvent::GatesPassed {
            feature_branch: fb("feature/story-2"),
            commits_ahead: nz(5),
        },
    )
    .unwrap();
    assert!(matches!(s, Stage::Merge { .. }));
}

#[test]
fn qa_retry_loop() {
    let s = Stage::Coding;
    let s = transition(s, PipelineEvent::GatesStarted).unwrap();
    assert!(matches!(s, Stage::Qa));

    let s = transition(
        s,
        PipelineEvent::GatesFailed {
            reason: "tests failed".into(),
        },
    )
    .unwrap();
    assert!(matches!(s, Stage::Coding));
}

// ── Bug 519: Merge with zero commits is unrepresentable ─────────────

#[test]
fn merge_with_zero_commits_is_unrepresentable() {
    assert!(NonZeroU32::new(0).is_none());
}

// ── Invalid transitions ─────────────────────────────────────────────

#[test]
fn cannot_jump_backlog_to_done() {
    let result = transition(Stage::Backlog, PipelineEvent::Accepted);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_unblock_done_story() {
    let s = Stage::Done {
        merged_at: chrono::Utc::now(),
        merge_commit: sha("abc"),
    };
    let result = transition(s, PipelineEvent::Unblock);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_unblock_review_held_story() {
    let s = Stage::Archived {
        archived_at: chrono::Utc::now(),
        reason: ArchiveReason::ReviewHeld {
            reason: "TBD".into(),
        },
    };
    let result = transition(s, PipelineEvent::Unblock);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_merge_from_backlog() {
    let result = transition(
        Stage::Backlog,
        PipelineEvent::MergeSucceeded {
            merge_commit: sha("abc"),
        },
    );
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_start_gates_from_backlog() {
    let result = transition(Stage::Backlog, PipelineEvent::GatesStarted);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_accept_from_coding() {
    let result = transition(Stage::Coding, PipelineEvent::Accepted);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

// ── Block from any active stage ─────────────────────────────────────

#[test]
fn block_from_any_active_stage() {
    for s in [Stage::Backlog, Stage::Coding, Stage::Qa] {
        let result = transition(
            s.clone(),
            PipelineEvent::Block {
                reason: "stuck".into(),
            },
        );
        assert!(matches!(
            result,
            Ok(Stage::Archived {
                reason: ArchiveReason::Blocked { .. },
                ..
            })
        ));
    }

    let m = Stage::Merge {
        feature_branch: fb("f"),
        commits_ahead: nz(1),
    };
    let result = transition(
        m,
        PipelineEvent::Block {
            reason: "stuck".into(),
        },
    );
    assert!(matches!(
        result,
        Ok(Stage::Archived {
            reason: ArchiveReason::Blocked { .. },
            ..
        })
    ));
}

#[test]
fn unblock_returns_to_backlog() {
    let s = Stage::Archived {
        archived_at: chrono::Utc::now(),
        reason: ArchiveReason::Blocked {
            reason: "test".into(),
        },
    };
    let result = transition(s, PipelineEvent::Unblock).unwrap();
    assert!(matches!(result, Stage::Backlog));
}

// ── Abandon / supersede ─────────────────────────────────────────────

#[test]
fn abandon_from_any_active_or_done() {
    for s in [
        Stage::Backlog,
        Stage::Coding,
        Stage::Qa,
        Stage::Done {
            merged_at: chrono::Utc::now(),
            merge_commit: sha("x"),
        },
    ] {
        let result = transition(s, PipelineEvent::Abandon);
        assert!(matches!(
            result,
            Ok(Stage::Archived {
                reason: ArchiveReason::Abandoned,
                ..
            })
        ));
    }
}

#[test]
fn supersede_from_any_active_or_done() {
    for s in [
        Stage::Backlog,
        Stage::Coding,
        Stage::Qa,
        Stage::Done {
            merged_at: chrono::Utc::now(),
            merge_commit: sha("x"),
        },
    ] {
        let result = transition(
            s,
            PipelineEvent::Supersede {
                by: sid("999_story_new"),
            },
        );
        assert!(matches!(
            result,
            Ok(Stage::Archived {
                reason: ArchiveReason::Superseded { .. },
                ..
            })
        ));
    }
}

// ── Review hold ─────────────────────────────────────────────────────

#[test]
fn review_hold_from_active_stages() {
    for s in [Stage::Backlog, Stage::Coding, Stage::Qa] {
        let result = transition(
            s.clone(),
            PipelineEvent::ReviewHold {
                reason: "review".into(),
            },
        );
        assert!(matches!(
            result,
            Ok(Stage::Archived {
                reason: ArchiveReason::ReviewHeld { .. },
                ..
            })
        ));
    }
}

// ── Merge failed final ──────────────────────────────────────────────

#[test]
fn merge_failed_final() {
    let s = Stage::Merge {
        feature_branch: fb("f"),
        commits_ahead: nz(1),
    };
    let result = transition(
        s,
        PipelineEvent::MergeFailedFinal {
            reason: "conflicts".into(),
        },
    )
    .unwrap();
    assert!(matches!(
        result,
        Stage::Archived {
            reason: ArchiveReason::MergeFailed { .. },
            ..
        }
    ));
}

#[test]
fn merge_failed_only_from_merge() {
    let result = transition(
        Stage::Coding,
        PipelineEvent::MergeFailedFinal {
            reason: "conflicts".into(),
        },
    );
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

// ── Execution state machine ─────────────────────────────────────────

#[test]
fn execution_happy_path() {
    let e = ExecutionState::Idle;
    let e = execution_transition(
        e,
        ExecutionEvent::SpawnRequested {
            agent: AgentName("coder-1".into()),
        },
    )
    .unwrap();
    assert!(matches!(e, ExecutionState::Pending { .. }));

    let e = execution_transition(e, ExecutionEvent::SpawnedSuccessfully).unwrap();
    assert!(matches!(e, ExecutionState::Running { .. }));

    let e = execution_transition(e, ExecutionEvent::Heartbeat).unwrap();
    assert!(matches!(e, ExecutionState::Running { .. }));

    let e = execution_transition(e, ExecutionEvent::Exited { exit_code: 0 }).unwrap();
    assert!(matches!(e, ExecutionState::Completed { exit_code: 0, .. }));
}

#[test]
fn execution_rate_limit_then_resume() {
    let e = ExecutionState::Running {
        agent: AgentName("coder-1".into()),
        started_at: chrono::Utc::now(),
        last_heartbeat: chrono::Utc::now(),
    };
    let e = execution_transition(
        e,
        ExecutionEvent::HitRateLimit {
            resume_at: chrono::Utc::now() + chrono::Duration::minutes(5),
        },
    )
    .unwrap();
    assert!(matches!(e, ExecutionState::RateLimited { .. }));

    let e = execution_transition(e, ExecutionEvent::SpawnedSuccessfully).unwrap();
    assert!(matches!(e, ExecutionState::Running { .. }));
}

#[test]
fn execution_stop_from_anywhere() {
    let e = ExecutionState::Running {
        agent: AgentName("coder-1".into()),
        started_at: chrono::Utc::now(),
        last_heartbeat: chrono::Utc::now(),
    };
    let e = execution_transition(e, ExecutionEvent::Stopped).unwrap();
    assert!(matches!(e, ExecutionState::Idle));
}

// ── Projection tests ────────────────────────────────────────────────

#[test]
fn bug_502_agent_not_in_stage() {
    // Bug 502 was caused by a coder agent being assigned to a story in
    // Merge stage. In the typed system, Stage has no `agent` field at all.
    // Agent assignment is per-node ExecutionState. This test documents that
    // the old failure mode is structurally impossible.
    let merge = Stage::Merge {
        feature_branch: BranchName("feature/story-1".into()),
        commits_ahead: NonZeroU32::new(3).unwrap(),
    };
    // Stage::Merge has exactly two fields: feature_branch and commits_ahead.
    // There is no way to attach an agent name to it. The type system
    // prevents bug 502 by construction.
    assert!(matches!(merge, Stage::Merge { .. }));
}

// ── TransitionError Display ─────────────────────────────────────────

#[test]
fn transition_error_display() {
    let err = TransitionError::InvalidTransition {
        from_stage: "Backlog".into(),
        event: "Accepted".into(),
    };
    assert_eq!(err.to_string(), "invalid transition: Backlog + Accepted");
}

// ── Upcoming / Triage ──────────────────────────────────────────────

#[test]
fn triage_upcoming_to_backlog() {
    let s = Stage::Upcoming;
    let s = transition(s, PipelineEvent::Triage).unwrap();
    assert!(matches!(s, Stage::Backlog));
}

#[test]
fn cannot_triage_from_backlog() {
    let result = transition(Stage::Backlog, PipelineEvent::Triage);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn abandon_from_upcoming() {
    let result = transition(Stage::Upcoming, PipelineEvent::Abandon).unwrap();
    assert!(matches!(
        result,
        Stage::Archived {
            reason: ArchiveReason::Abandoned,
            ..
        }
    ));
}

#[test]
fn supersede_from_upcoming() {
    let result = transition(
        Stage::Upcoming,
        PipelineEvent::Supersede {
            by: sid("999_story_new"),
        },
    )
    .unwrap();
    assert!(matches!(
        result,
        Stage::Archived {
            reason: ArchiveReason::Superseded { .. },
            ..
        }
    ));
}

#[test]
fn cannot_deps_met_from_upcoming() {
    let result = transition(Stage::Upcoming, PipelineEvent::DepsMet);
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

// ── Reject ─────────────────────────────────────────────────────────

#[test]
fn reject_from_active_stages() {
    for s in [Stage::Backlog, Stage::Coding, Stage::Qa] {
        let result = transition(
            s.clone(),
            PipelineEvent::Reject {
                reason: "not needed".into(),
            },
        );
        assert!(matches!(
            result,
            Ok(Stage::Archived {
                reason: ArchiveReason::Rejected { .. },
                ..
            })
        ));
    }

    let m = Stage::Merge {
        feature_branch: fb("f"),
        commits_ahead: nz(1),
    };
    let result = transition(
        m,
        PipelineEvent::Reject {
            reason: "not needed".into(),
        },
    );
    assert!(matches!(
        result,
        Ok(Stage::Archived {
            reason: ArchiveReason::Rejected { .. },
            ..
        })
    ));
}

#[test]
fn cannot_reject_from_done() {
    let s = Stage::Done {
        merged_at: chrono::Utc::now(),
        merge_commit: sha("abc"),
    };
    let result = transition(
        s,
        PipelineEvent::Reject {
            reason: "too late".into(),
        },
    );
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

#[test]
fn cannot_reject_from_archived() {
    let s = Stage::Archived {
        archived_at: chrono::Utc::now(),
        reason: ArchiveReason::Completed,
    };
    let result = transition(
        s,
        PipelineEvent::Reject {
            reason: "already done".into(),
        },
    );
    assert!(matches!(
        result,
        Err(TransitionError::InvalidTransition { .. })
    ));
}

// ── ProjectionError Display ─────────────────────────────────────────