package pathway

import (
	"encoding/json"
	"errors"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
)

// Closes Sprint 2 design-bar work from the audit. Tests cover all 7
// claim rows from claim-coverage-table.md: ADD, UPDATE, REVISE,
// RETIRE, HISTORY chain cycle-safe, replay-count duplicate ADD,
// corrupted memory row recovery (corrupted_test.go).

// newTestStore returns an in-memory Store with deterministic UID +
// time generation for repeatable assertions.
func newTestStore(t *testing.T) *Store {
	t.Helper()
	s := NewStore(nil)
	var counter int
	var clock int64
	s.uidFn = func() string {
		counter++
		return "uid-" + strconv.Itoa(counter)
	}
	s.nowFn = func() int64 {
		clock++
		return clock
	}
	return s
}

func newPersistedStore(t *testing.T) (*Store, string) {
	t.Helper()
	dir := t.TempDir()
	path := filepath.Join(dir, "pathway.jsonl")
	p, err := NewPersistor(path)
	if err != nil {
		t.Fatalf("NewPersistor: %v", err)
	}
	s := NewStore(p)
	var counter int
	var clock int64
	s.uidFn = func() string {
		counter++
		return "uid-" + strconv.Itoa(counter)
	}
	s.nowFn = func() int64 {
		clock++
		return clock
	}
	return s, path
}

// ── Sprint 2 row 1: ADD a new pathway trace ────────────────────

func TestAdd_AssignsUIDAndTimestamps(t *testing.T) {
	s := newTestStore(t)
	tr, err := s.Add(json.RawMessage(`{"k":"v"}`), "tag-a")
	if err != nil {
		t.Fatalf("Add: %v", err)
	}
	if tr.UID != "uid-1" {
		t.Errorf("UID = %q, want uid-1", tr.UID)
	}
	if tr.ReplayCount != 1 {
		t.Errorf("ReplayCount = %d, want 1", tr.ReplayCount)
	}
	if tr.Retired {
		t.Error("freshly-added trace should NOT be retired")
	}
	if tr.CreatedAtNs == 0 || tr.UpdatedAtNs == 0 {
		t.Error("timestamps unset")
	}
	if len(tr.Tags) != 1 || tr.Tags[0] != "tag-a" {
		t.Errorf("Tags = %v, want [tag-a]", tr.Tags)
	}
}

func TestAdd_RejectsInvalidJSON(t *testing.T) {
	s := newTestStore(t)
	_, err := s.Add(json.RawMessage(`not json`))
	if !errors.Is(err, ErrInvalidContent) {
		t.Errorf("expected ErrInvalidContent, got %v", err)
	}
}

// ── Sprint 2 row 2: UPDATE replaces existing trace by uid ──────

func TestUpdate_ReplacesContentSameUID(t *testing.T) {
	s := newTestStore(t)
	tr, _ := s.Add(json.RawMessage(`{"v":1}`))

	if err := s.Update(tr.UID, json.RawMessage(`{"v":2}`)); err != nil {
		t.Fatalf("Update: %v", err)
	}

	got, _ := s.Get(tr.UID)
	if string(got.Content) != `{"v":2}` {
		t.Errorf("content = %s, want updated", got.Content)
	}
	if got.UpdatedAtNs == tr.UpdatedAtNs {
		t.Error("UpdatedAtNs should bump on Update")
	}
}

func TestUpdate_MissingUID_Errors(t *testing.T) {
	s := newTestStore(t)
	err := s.Update("nonexistent", json.RawMessage(`{}`))
	if !errors.Is(err, ErrNotFound) {
		t.Errorf("expected ErrNotFound, got %v", err)
	}
}

// ── Sprint 2 row 3: REVISE creates a new revision linked via history ──

func TestRevise_LinksToPredecessorViaHistory(t *testing.T) {
	s := newTestStore(t)
	root, _ := s.Add(json.RawMessage(`{"v":1}`))
	rev, err := s.Revise(root.UID, json.RawMessage(`{"v":2}`))
	if err != nil {
		t.Fatalf("Revise: %v", err)
	}
	if rev.PredecessorUID != root.UID {
		t.Errorf("PredecessorUID = %q, want %q", rev.PredecessorUID, root.UID)
	}
	if rev.UID == root.UID {
		t.Error("Revise must produce a NEW UID")
	}
}

func TestRevise_PredecessorMissing_Errors(t *testing.T) {
	s := newTestStore(t)
	_, err := s.Revise("ghost-uid", json.RawMessage(`{}`))
	if !errors.Is(err, ErrPredecessorMissing) {
		t.Errorf("expected ErrPredecessorMissing, got %v", err)
	}
}

func TestRevise_ChainOfThree_BackwardWalk(t *testing.T) {
	s := newTestStore(t)
	a, _ := s.Add(json.RawMessage(`{"v":1}`))
	b, _ := s.Revise(a.UID, json.RawMessage(`{"v":2}`))
	c, _ := s.Revise(b.UID, json.RawMessage(`{"v":3}`))

	chain, err := s.History(c.UID)
	if err != nil {
		t.Fatalf("History: %v", err)
	}
	want := []string{c.UID, b.UID, a.UID}
	if len(chain) != 3 {
		t.Fatalf("chain length = %d, want 3", len(chain))
	}
	for i, tr := range chain {
		if tr.UID != want[i] {
			t.Errorf("chain[%d].UID = %q, want %q", i, tr.UID, want[i])
		}
	}
}

// ── Sprint 2 row 4: RETIRE marks trace excluded from retrieval ──

func TestRetire_ExcludedFromSearch(t *testing.T) {
	s := newTestStore(t)
	a, _ := s.Add(json.RawMessage(`{"v":1}`), "common")
	b, _ := s.Add(json.RawMessage(`{"v":2}`), "common")
	if err := s.Retire(a.UID); err != nil {
		t.Fatalf("Retire: %v", err)
	}

	results := s.Search(SearchFilter{Tag: "common"})
	if len(results) != 1 || results[0].UID != b.UID {
		t.Errorf("Search excluded retired? got %d results, want 1 (active only)", len(results))
	}

	// IncludeRetired flag returns both.
	withRetired := s.Search(SearchFilter{Tag: "common", IncludeRetired: true})
	if len(withRetired) != 2 {
		t.Errorf("IncludeRetired Search returned %d, want 2", len(withRetired))
	}
}

func TestRetire_StillAccessibleViaGet(t *testing.T) {
	// Per ADR-004: "Retired traces are excluded from Search by default
	// but accessible via Get and History." Locks that contract.
	s := newTestStore(t)
	tr, _ := s.Add(json.RawMessage(`{"v":1}`))
	s.Retire(tr.UID)

	got, err := s.Get(tr.UID)
	if err != nil {
		t.Fatalf("retired trace Get: %v", err)
	}
	if !got.Retired {
		t.Error("Get should preserve retired flag")
	}
}

func TestRetire_StillAccessibleViaHistory(t *testing.T) {
	s := newTestStore(t)
	a, _ := s.Add(json.RawMessage(`{"v":1}`))
	b, _ := s.Revise(a.UID, json.RawMessage(`{"v":2}`))
	s.Retire(a.UID)

	chain, err := s.History(b.UID)
	if err != nil {
		t.Fatalf("History: %v", err)
	}
	if len(chain) != 2 {
		t.Errorf("chain length = %d, want 2 (revision + retired root)", len(chain))
	}
	if !chain[1].Retired {
		t.Error("retired predecessor should still appear in History with Retired=true")
	}
}

// ── Sprint 2 row 5: HISTORY chain is cycle-safe ────────────────

func TestHistory_CycleDetected(t *testing.T) {
	// Cycles can't form via the public API (new UIDs every Revise),
	// but corruption could create one. Inject one directly into the
	// internal map and verify History rejects it.
	s := newTestStore(t)
	s.traces["A"] = &Trace{UID: "A", PredecessorUID: "B"}
	s.traces["B"] = &Trace{UID: "B", PredecessorUID: "A"}

	_, err := s.History("A")
	if !errors.Is(err, ErrCycle) {
		t.Errorf("expected ErrCycle, got %v", err)
	}
}

func TestHistory_PredecessorMissing_TruncatesChain(t *testing.T) {
	s := newTestStore(t)
	tr := &Trace{UID: "X", PredecessorUID: "ghost"}
	s.traces["X"] = tr

	chain, err := s.History("X")
	if err != nil {
		t.Fatalf("History on partial chain: %v", err)
	}
	if len(chain) != 1 {
		t.Errorf("partial chain returned %d, want 1 (truncate at missing predecessor)", len(chain))
	}
}

func TestHistory_UnknownUID_ErrorsClean(t *testing.T) {
	s := newTestStore(t)
	_, err := s.History("nope")
	if !errors.Is(err, ErrNotFound) {
		t.Errorf("expected ErrNotFound, got %v", err)
	}
}

// ── Sprint 2 row 6: replay_count increments on duplicate ADD ───

func TestAddIdempotent_IncrementsReplayCount(t *testing.T) {
	s := newTestStore(t)

	first, err := s.AddIdempotent("custom-uid", json.RawMessage(`{"v":1}`))
	if err != nil {
		t.Fatalf("first AddIdempotent: %v", err)
	}
	if first.ReplayCount != 1 {
		t.Errorf("first ReplayCount = %d, want 1", first.ReplayCount)
	}

	second, err := s.AddIdempotent("custom-uid", json.RawMessage(`{"v":"different"}`))
	if err != nil {
		t.Fatalf("second AddIdempotent: %v", err)
	}
	if second.ReplayCount != 2 {
		t.Errorf("after second add, ReplayCount = %d, want 2", second.ReplayCount)
	}

	// Original content preserved (replay does NOT overwrite).
	if !strings.Contains(string(second.Content), "v") ||
		!strings.Contains(string(second.Content), "1") {
		t.Errorf("replay should preserve original content, got %s", second.Content)
	}
}

func TestAddIdempotent_RejectsEmptyUID(t *testing.T) {
	s := newTestStore(t)
	_, err := s.AddIdempotent("", json.RawMessage(`{}`))
	if !errors.Is(err, ErrEmptyUID) {
		t.Errorf("expected ErrEmptyUID, got %v", err)
	}
}

// ── Sprint 2 row 7: corrupted memory row recovery ─────────────

func TestPersistor_RoundTrip(t *testing.T) {
	s, path := newPersistedStore(t)

	a, _ := s.Add(json.RawMessage(`{"v":1}`), "alpha")
	b, _ := s.Revise(a.UID, json.RawMessage(`{"v":2}`), "alpha")
	s.Retire(a.UID)
	_ = b

	// Open fresh store against same file, replay.
	p, _ := NewPersistor(path)
	s2 := NewStore(p)
	n, err := s2.Load()
	if err != nil {
		t.Fatalf("Load: %v", err)
	}
	if n != 3 {
		t.Errorf("replayed %d events, want 3", n)
	}
	stats := s2.Stats()
	if stats.Total != 2 {
		t.Errorf("Stats.Total = %d, want 2", stats.Total)
	}
	if stats.Retired != 1 {
		t.Errorf("Stats.Retired = %d, want 1", stats.Retired)
	}

	got, _ := s2.Get(a.UID)
	if !got.Retired {
		t.Error("retired flag lost across persistence round-trip")
	}
}

// ── Search filter coverage ─────────────────────────────────────

func TestSearch_TagFilter(t *testing.T) {
	s := newTestStore(t)
	s.Add(json.RawMessage(`{"v":1}`), "production")
	s.Add(json.RawMessage(`{"v":2}`), "test")
	s.Add(json.RawMessage(`{"v":3}`), "production", "edge")

	prodHits := s.Search(SearchFilter{Tag: "production"})
	if len(prodHits) != 2 {
		t.Errorf("tag=production returned %d, want 2", len(prodHits))
	}

	edgeHits := s.Search(SearchFilter{Tag: "edge"})
	if len(edgeHits) != 1 {
		t.Errorf("tag=edge returned %d, want 1", len(edgeHits))
	}
}

func TestSearch_ContentContainsFilter(t *testing.T) {
	s := newTestStore(t)
	s.Add(json.RawMessage(`{"role":"welder","city":"Chicago"}`))
	s.Add(json.RawMessage(`{"role":"electrician","city":"Detroit"}`))
	s.Add(json.RawMessage(`{"role":"safety","city":"Chicago"}`))

	chi := s.Search(SearchFilter{ContentContains: "Chicago"})
	if len(chi) != 2 {
		t.Errorf("ContentContains=Chicago returned %d, want 2", len(chi))
	}
}

func TestStats_TracksAllStates(t *testing.T) {
	s := newTestStore(t)
	a, _ := s.Add(json.RawMessage(`{}`))
	s.Add(json.RawMessage(`{}`))
	s.Add(json.RawMessage(`{}`))
	s.Retire(a.UID)

	st := s.Stats()
	if st.Total != 3 {
		t.Errorf("Total = %d, want 3", st.Total)
	}
	if st.Active != 2 {
		t.Errorf("Active = %d, want 2", st.Active)
	}
	if st.Retired != 1 {
		t.Errorf("Retired = %d, want 1", st.Retired)
	}
}

// ── Concurrency safety ────────────────────────────────────────

func TestStore_ConcurrentAdd(t *testing.T) {
	s := newTestStore(t)
	const N = 100
	done := make(chan bool, N)
	for i := 0; i < N; i++ {
		go func() {
			_, err := s.Add(json.RawMessage(`{"x":1}`))
			if err != nil {
				t.Errorf("concurrent Add: %v", err)
			}
			done <- true
		}()
	}
	for i := 0; i < N; i++ {
		<-done
	}
	if s.Stats().Total != N {
		t.Errorf("after %d concurrent Adds, Total = %d", N, s.Stats().Total)
	}
}