//! 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::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::Blocked { .. })));
}

#[test]
fn unblock_returns_to_coding() {
    let s = Stage::Blocked {
        reason: "test".into(),
    };
    let result = transition(s, PipelineEvent::Unblock).unwrap();
    assert!(matches!(result, Stage::Coding));
}

#[test]
fn blocked_demote_returns_to_backlog() {
    // Stuck-story parking lane: `Blocked + Demote → Backlog` lets operators
    // move a blocked story back to the backlog without losing it to
    // Archived. Complements `Blocked + Unblock → Coding` which re-enters
    // active work.
    let s = Stage::Blocked {
        reason: "waiting on dep".into(),
    };
    let result = transition(s, PipelineEvent::Demote).unwrap();
    assert!(matches!(result, Stage::Backlog));
}

#[test]
fn cannot_demote_from_done() {
    // Sanity: Demote remains illegal from terminal/archived stages — the
    // new `Blocked + Demote → Backlog` rule must NOT broaden it further.
    let s = Stage::Done {
        merged_at: chrono::Utc::now(),
        merge_commit: sha("x"),
    };
    assert!(matches!(
        transition(s, PipelineEvent::Demote),
        Err(TransitionError::InvalidTransition { .. })
    ));
}

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

#[test]
fn legacy_unblock_archived_blocked_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 { .. })
    ));
}

// ── Freeze / Unfreeze (story 934, stage 4: orthogonal flag) ────────────────

/// Freeze sets the `frozen` flag without changing the stage register.
/// Unfreeze clears the flag — the stage was never touched so there's nothing
/// to "restore". Tests the freeze/unfreeze API on the apply layer, since
/// freeze/unfreeze are no longer pure stage transitions.
#[test]
fn freeze_sets_flag_without_changing_stage() {
    crate::crdt_state::init_for_test();
    crate::db::ensure_content_store();

    let story_id = "9950_story_freeze_regression";
    crate::db::write_item_with_content(
        story_id,
        "2_current",
        "---\nname: Freeze Regression\n---\n# Story\n",
        crate::db::ItemMeta::named("Freeze Regression"),
    );

    let item = read_typed(story_id).unwrap().unwrap();
    assert!(matches!(item.stage, Stage::Coding));
    assert!(!item.is_frozen());

    super::apply::transition_to_frozen(story_id).expect("freeze should succeed");

    let item = read_typed(story_id).unwrap().unwrap();
    assert!(
        matches!(item.stage, Stage::Coding),
        "stage register stays at Coding after freeze: {:?}",
        item.stage
    );
    assert!(item.is_frozen(), "frozen flag should be set after freeze");

    super::apply::transition_to_unfrozen(story_id).expect("unfreeze should succeed");

    let item = read_typed(story_id).unwrap().unwrap();
    assert!(
        matches!(item.stage, Stage::Coding),
        "stage register still at Coding after unfreeze: {:?}",
        item.stage
    );
    assert!(
        !item.is_frozen(),
        "frozen flag should be cleared after unfreeze"
    );
}

// ── Story 868: MergeFailure regression ─────────────────────────────

/// Regression test (story 868): applying `PipelineEvent::MergeFailed` to a story
/// in `Stage::Merge` transitions it to `Stage::MergeFailure` and the emitted
/// `TransitionFired` event carries the full reason string in its payload.
#[test]
fn merge_failure_transition_emits_event_with_full_reason() {
    crate::crdt_state::init_for_test();
    crate::db::ensure_content_store();

    let story_id = "99868_story_merge_failure_event";
    crate::db::write_item_with_content(
        story_id,
        "4_merge",
        "---\nname: Merge Failure Event Test\n---\n# Story\n",
        crate::db::ItemMeta::named("Merge Failure Event Test"),
    );

    let reason = "Conflict in server/src/main.rs: both modified";
    let fired = super::apply::apply_transition(
        story_id,
        PipelineEvent::MergeFailed {
            reason: reason.to_string(),
        },
        None,
    )
    .expect("MergeFailed transition should succeed");

    // The emitted event payload carries the full reason string.
    match &fired.event {
        PipelineEvent::MergeFailed { reason: r } => {
            assert_eq!(r, reason, "emitted event should carry the full reason");
        }
        other => panic!("expected MergeFailed event, got: {other:?}"),
    }

    // The story transitioned to MergeFailure.
    assert!(
        matches!(fired.after, Stage::MergeFailure { .. }),
        "after-stage should be MergeFailure: {:?}",
        fired.after
    );

    // Verify CRDT reflects the new stage.
    let item = read_typed(story_id)
        .expect("CRDT read should succeed")
        .expect("item should exist");
    assert_eq!(
        item.stage.dir_name(),
        "merge_failure",
        "CRDT stage should be 4_merge_failure"
    );
}

// ── Story 913: MergeFailure + MergeFailed self-loop ────────────────

/// AC1: `MergeFailure + MergeFailed` is a valid self-transition — no error logged.
#[test]
fn merge_failure_plus_merge_failed_is_self_loop() {
    let s = Stage::MergeFailure {
        reason: "initial failure".into(),
    };
    let result = transition(
        s,
        PipelineEvent::MergeFailed {
            reason: "second failure".into(),
        },
    );
    assert!(
        matches!(result, Ok(Stage::MergeFailure { .. })),
        "MergeFailure + MergeFailed should self-loop to MergeFailure, got: {result:?}"
    );
}

/// AC2 + AC3: applying `MergeFailed` to a story already in `MergeFailure` succeeds and
/// the `TransitionFired::before` is `MergeFailure`, allowing callers to suppress the
/// duplicate notification.
#[test]
fn repeated_merge_failure_apply_transition_no_error_no_duplicate_notification() {
    crate::crdt_state::init_for_test();
    crate::db::ensure_content_store();

    let story_id = "99913_story_merge_failure_selfloop";
    crate::db::write_item_with_content(
        story_id,
        "merge_failure",
        "---\nname: MergeFailure Self-loop Test\n---\n# Story\n",
        crate::db::ItemMeta::named("MergeFailure Self-loop Test"),
    );

    // Apply a second MergeFailed to a story already in MergeFailure.
    let fired = super::apply::apply_transition(
        story_id,
        PipelineEvent::MergeFailed {
            reason: "duplicate failure".into(),
        },
        None,
    )
    .expect("MergeFailed on already-failed story should succeed without error");

    // The before-stage was MergeFailure: this was a self-loop.
    // Callers check this to decide whether to suppress the chat notification.
    assert!(
        matches!(fired.before, Stage::MergeFailure { .. }),
        "fired.before should be MergeFailure (self-loop): {:?}",
        fired.before
    );
    assert!(
        matches!(fired.after, Stage::MergeFailure { .. }),
        "fired.after should remain MergeFailure: {:?}",
        fired.after
    );

    // Verify the CRDT stage is still merge_failure.
    let item = read_typed(story_id)
        .expect("CRDT read should succeed")
        .expect("item should still exist");
    assert_eq!(
        item.stage.dir_name(),
        "merge_failure",
        "CRDT stage should remain merge_failure after self-loop"
    );

    // Simulate the caller's de-dup logic: since fired.before is already MergeFailure,
    // no notification should be dispatched.
    let should_notify = !matches!(fired.before, Stage::MergeFailure { .. });
    assert!(
        !should_notify,
        "should_notify must be false for a self-loop to prevent duplicate notification"
    );
}

// ── Story 892: MergeFailure → Done (manual recovery) ───────────────

/// Regression test (story 892): `accept_story` on a story in `MergeFailure`
/// transitions it to `Done` and emits a `TransitionFired` event.
#[test]
fn merge_failure_accept_pure_transition() {
    let s = Stage::MergeFailure {
        reason: "conflicts unresolvable".into(),
    };
    let result = transition(s, PipelineEvent::Accepted).unwrap();
    assert!(
        matches!(result, Stage::Done { .. }),
        "MergeFailure + Accepted should yield Done, got: {result:?}"
    );
}

/// Regression test (story 892): `apply_transition` on a CRDT-stored `MergeFailure`
/// story moves it to `Done` and the emitted `TransitionFired` event is present.
#[test]
fn merge_failure_accept_moves_to_done_via_crdt() {
    crate::crdt_state::init_for_test();
    crate::db::ensure_content_store();

    let story_id = "99892_story_merge_failure_accept";
    crate::db::write_item_with_content(
        story_id,
        "merge_failure",
        "---\nname: MergeFailure Accept Test\n---\n# Story\n",
        crate::db::ItemMeta::named("MergeFailure Accept Test"),
    );

    let fired = super::apply::apply_transition(story_id, PipelineEvent::Accepted, None)
        .expect("MergeFailure + Accepted should succeed");

    // The before-stage was MergeFailure.
    assert!(
        matches!(fired.before, Stage::MergeFailure { .. }),
        "fired.before should be MergeFailure: {:?}",
        fired.before
    );

    // The after-stage is Done.
    assert!(
        matches!(fired.after, Stage::Done { .. }),
        "fired.after should be Done: {:?}",
        fired.after
    );

    // TransitionFired carries the Accepted event.
    assert!(
        matches!(fired.event, PipelineEvent::Accepted),
        "fired.event should be Accepted: {:?}",
        fired.event
    );

    // CRDT reflects done.
    let item = read_typed(story_id)
        .expect("CRDT read should succeed")
        .expect("item should exist");
    assert_eq!(
        item.stage.dir_name(),
        "done",
        "CRDT stage should be done after MergeFailure + Accepted"
    );
}

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