package repository

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"testing"

	"github.com/google/uuid"
	"github.com/joho/godotenv"
	"github.com/prabhupadasays/spsays-bff/internal/model"
	"go.uber.org/zap"
)

// These exercise real SQL against a real Postgres — the LATERAL joins, the
// FOR UPDATE sequencing and the partial indexes are the parts most likely to be
// wrong, and none of them can be checked without a database. Skipped when no
// POSTGRES_URI is configured, so `go test ./...` still passes anywhere.
func testRepo(t *testing.T) (*ChatRepo, *Postgres) {
	t.Helper()
	uri := os.Getenv("POSTGRES_URI")
	if uri == "" {
		_ = godotenv.Load(filepath.Join("..", "..", ".env"))
		uri = os.Getenv("POSTGRES_URI")
	}
	if uri == "" {
		t.Skip("POSTGRES_URI not set — skipping chat repository integration tests")
	}
	pg, err := NewPostgres(context.Background(), uri, zap.NewNop())
	if err != nil {
		t.Skipf("postgres unreachable: %v", err)
	}
	t.Cleanup(pg.Close)
	return NewChatRepo(pg), pg
}

// makeUser inserts a throwaway user and removes it (and anything cascading
// from it) when the test finishes.
func makeUser(t *testing.T, pg *Postgres, label string) string {
	t.Helper()
	ctx := context.Background()
	id := uuid.NewString()
	suffix := id[:8]
	_, err := pg.Pool.Exec(ctx, `
		INSERT INTO users (id, email, password_hash, name, handle)
		VALUES ($1, $2, 'x', $3, $4)`,
		id, fmt.Sprintf("chattest-%s@example.invalid", suffix), "Chat Test "+label, "chattest_"+suffix)
	if err != nil {
		t.Fatalf("create test user: %v", err)
	}
	t.Cleanup(func() {
		_, _ = pg.Pool.Exec(context.Background(), `DELETE FROM users WHERE id = $1`, id)
	})
	return id
}

// dropConversation removes a thread when the test ends; messages, participants
// and attachments cascade with it.
func dropConversation(t *testing.T, pg *Postgres, id string) {
	t.Cleanup(func() {
		_, _ = pg.Pool.Exec(context.Background(), `DELETE FROM conversations WHERE id = $1`, id)
	})
}

func send(t *testing.T, r *ChatRepo, convID, sender, body string) *model.Message {
	t.Helper()
	m, _, err := r.Append(context.Background(), AppendParams{
		ConversationID: convID, SenderID: &sender, Kind: model.MessageText, Body: body,
	})
	if err != nil {
		t.Fatalf("append %q: %v", body, err)
	}
	return m
}

func TestEnsureDM_IsIdempotentFromEitherSide(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")

	first, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatalf("EnsureDM: %v", err)
	}
	dropConversation(t, pg, first.ID)

	// Same pair, opposite argument order — must resolve to the same thread,
	// which is the whole point of the sorted dm_key.
	second, err := r.EnsureDM(ctx, b, a)
	if err != nil {
		t.Fatalf("EnsureDM reversed: %v", err)
	}
	if second.ID != first.ID {
		t.Errorf("reversed EnsureDM made a second thread: %s vs %s", second.ID, first.ID)
	}

	for _, u := range []string{a, b} {
		if _, err := r.Participant(ctx, first.ID, u); err != nil {
			t.Errorf("user %s is not a participant: %v", u, err)
		}
	}
}

func TestParticipant_RejectsOutsiders(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b, outsider := makeUser(t, pg, "A"), makeUser(t, pg, "B"), makeUser(t, pg, "C")

	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)

	if _, err := r.Participant(ctx, c.ID, outsider); !errors.Is(err, ErrNotParticipant) {
		t.Errorf("outsider got %v, want ErrNotParticipant", err)
	}
}

func TestAppend_AssignsGaplessSequence(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)

	for i := int64(1); i <= 3; i++ {
		m := send(t, r, c.ID, a, fmt.Sprintf("msg %d", i))
		if m.Seq != i {
			t.Errorf("message %d got seq %d", i, m.Seq)
		}
	}

	var lastSeq int64
	if err := pg.Pool.QueryRow(ctx, `SELECT last_seq FROM conversations WHERE id=$1`, c.ID).Scan(&lastSeq); err != nil {
		t.Fatal(err)
	}
	if lastSeq != 3 {
		t.Errorf("conversation.last_seq = %d, want 3", lastSeq)
	}
}

// A retried send must return the original message and must NOT burn a sequence
// number — a gap would break the client's catch-up cursor.
func TestAppend_DeduplicatesRetries(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)

	clientID := uuid.NewString()
	p := AppendParams{ConversationID: c.ID, SenderID: &a, Kind: model.MessageText,
		Body: "only once", ClientMsgID: &clientID}

	first, created, err := r.Append(ctx, p)
	if err != nil || !created {
		t.Fatalf("first append: created=%v err=%v", created, err)
	}
	again, created, err := r.Append(ctx, p)
	if err != nil {
		t.Fatalf("retry: %v", err)
	}
	if created {
		t.Error("retry reported created=true")
	}
	if again.ID != first.ID || again.Seq != first.Seq {
		t.Errorf("retry returned a different message: %s/%d vs %s/%d", again.ID, again.Seq, first.ID, first.Seq)
	}

	var count, lastSeq int64
	_ = pg.Pool.QueryRow(ctx, `SELECT count(*), max(seq) FROM messages WHERE conversation_id=$1`, c.ID).Scan(&count, &lastSeq)
	if count != 1 || lastSeq != 1 {
		t.Errorf("after retry: %d messages, last seq %d — want 1 and 1", count, lastSeq)
	}
}

func TestMessages_KeysetPaging(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)
	for i := 1; i <= 5; i++ {
		send(t, r, c.ID, a, fmt.Sprintf("m%d", i))
	}

	page1, err := r.Messages(ctx, c.ID, a, 0, 2)
	if err != nil {
		t.Fatal(err)
	}
	if len(page1) != 2 || page1[0].Seq != 5 || page1[1].Seq != 4 {
		t.Fatalf("page1 = %v, want seq 5,4", seqsOf(page1))
	}
	page2, err := r.Messages(ctx, c.ID, a, page1[len(page1)-1].Seq, 2)
	if err != nil {
		t.Fatal(err)
	}
	if len(page2) != 2 || page2[0].Seq != 3 || page2[1].Seq != 2 {
		t.Fatalf("page2 = %v, want seq 3,2", seqsOf(page2))
	}
	// entities must come back as a JSON array, never null — the client indexes
	// into it without a nil check.
	var spans []map[string]any
	if err := json.Unmarshal(page1[0].Entities, &spans); err != nil {
		t.Errorf("entities not valid JSON: %v (%s)", err, page1[0].Entities)
	}
}

// Delete-for-me must hide a message from that user's history AND from their
// inbox preview, while leaving it visible to everyone else.
func TestMessageHides_ArePerUser(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)
	send(t, r, c.ID, a, "keep")
	hidden := send(t, r, c.ID, a, "hide me")

	if _, err := pg.Pool.Exec(ctx,
		`INSERT INTO message_hides (message_id, user_id) VALUES ($1,$2)`, hidden.ID, a); err != nil {
		t.Fatal(err)
	}

	mine, _ := r.Messages(ctx, c.ID, a, 0, 10)
	if len(mine) != 1 || mine[0].Body != "keep" {
		t.Errorf("hider still sees %v", bodiesOf(mine))
	}
	theirs, _ := r.Messages(ctx, c.ID, b, 0, 10)
	if len(theirs) != 2 {
		t.Errorf("other participant sees %v, want both", bodiesOf(theirs))
	}

	inbox, err := r.Inbox(ctx, a, []string{model.ConversationDM}, 10)
	if err != nil {
		t.Fatal(err)
	}
	row := findConv(inbox, c.ID)
	if row == nil || row.LastMessage == nil {
		t.Fatal("conversation missing from hider's inbox")
	}
	if row.LastMessage.Body != "keep" {
		t.Errorf("hider's preview = %q, want the un-hidden message", row.LastMessage.Body)
	}
}

func TestInbox_UnreadPeerAndPreview(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)
	send(t, r, c.ID, a, "first")
	send(t, r, c.ID, a, "latest")

	// Recipient has read nothing.
	inbox, err := r.Inbox(ctx, b, []string{model.ConversationDM}, 10)
	if err != nil {
		t.Fatal(err)
	}
	row := findConv(inbox, c.ID)
	if row == nil {
		t.Fatal("thread missing from recipient inbox")
	}
	if row.Unread != 2 {
		t.Errorf("unread = %d, want 2", row.Unread)
	}
	if row.LastMessage == nil || row.LastMessage.Body != "latest" {
		t.Errorf("preview = %+v, want body %q", row.LastMessage, "latest")
	}
	if row.LastMessage != nil && row.LastMessage.SenderName == "" {
		t.Error("preview has no sender name — the inbox line needs it")
	}
	if row.Peer == nil || row.Peer.ID != a {
		t.Errorf("peer = %+v, want user A", row.Peer)
	}

	// The sender's own cursor advanced on send, so their unread is zero.
	senderInbox, _ := r.Inbox(ctx, a, []string{model.ConversationDM}, 10)
	if sr := findConv(senderInbox, c.ID); sr == nil || sr.Unread != 0 {
		t.Errorf("sender unread = %v, want 0", sr)
	}

	if err := r.MarkRead(ctx, c.ID, b, 2); err != nil {
		t.Fatal(err)
	}
	after, _ := r.Inbox(ctx, b, []string{model.ConversationDM}, 10)
	if row := findConv(after, c.ID); row == nil || row.Unread != 0 {
		t.Errorf("after MarkRead unread = %v, want 0", row)
	}
}

// Cursors must never move backwards: a replayed or out-of-order receipt would
// otherwise resurrect already-read messages as unread.
func TestCursors_NeverGoBackwards(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b := makeUser(t, pg, "A"), makeUser(t, pg, "B")
	c, err := r.EnsureDM(ctx, a, b)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, c.ID)
	for i := 0; i < 3; i++ {
		send(t, r, c.ID, a, "m")
	}

	if err := r.MarkRead(ctx, c.ID, b, 3); err != nil {
		t.Fatal(err)
	}
	if err := r.MarkRead(ctx, c.ID, b, 1); err != nil { // stale replay
		t.Fatal(err)
	}
	p, err := r.Participant(ctx, c.ID, b)
	if err != nil {
		t.Fatal(err)
	}
	if p.LastReadSeq != 3 {
		t.Errorf("last_read_seq = %d after a stale replay, want 3", p.LastReadSeq)
	}
	if p.LastDeliveredSeq != 3 {
		t.Errorf("reading should imply delivery: last_delivered_seq = %d, want 3", p.LastDeliveredSeq)
	}
}

func TestReceipts_ExcludeCallerAndUseMinimum(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a, b, cUser := makeUser(t, pg, "A"), makeUser(t, pg, "B"), makeUser(t, pg, "C")
	conv, err := r.CreateGroup(ctx, a, "Test group", []string{b, cUser})
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, conv.ID)
	for i := 0; i < 3; i++ {
		send(t, r, conv.ID, a, "m")
	}

	if err := r.MarkDelivered(ctx, conv.ID, b, 3); err != nil {
		t.Fatal(err)
	}
	if err := r.MarkRead(ctx, conv.ID, b, 3); err != nil {
		t.Fatal(err)
	}
	// C has received nothing yet.
	rc, err := r.Receipts(ctx, conv.ID, a)
	if err != nil {
		t.Fatal(err)
	}
	if rc.ReadSeq != 0 || rc.DeliveredSeq != 0 {
		t.Errorf("receipts = %+v, want zeros while one member is behind", rc)
	}

	if err := r.MarkRead(ctx, conv.ID, cUser, 3); err != nil {
		t.Fatal(err)
	}
	rc, _ = r.Receipts(ctx, conv.ID, a)
	if rc.ReadSeq != 3 || rc.DeliveredSeq != 3 {
		t.Errorf("receipts = %+v, want 3/3 once everyone has read", rc)
	}
}

func TestEnsureAIThread_OnePerUserAndSeparateTab(t *testing.T) {
	r, pg := testRepo(t)
	ctx := context.Background()
	a := makeUser(t, pg, "A")

	first, err := r.EnsureAIThread(ctx, a)
	if err != nil {
		t.Fatal(err)
	}
	dropConversation(t, pg, first.ID)
	again, err := r.EnsureAIThread(ctx, a)
	if err != nil {
		t.Fatal(err)
	}
	if again.ID != first.ID {
		t.Errorf("second call made another AI thread: %s vs %s", again.ID, first.ID)
	}

	// The tabs are a kind filter: an AI thread must not appear under Chats.
	chats, _ := r.Inbox(ctx, a, []string{model.ConversationDM, model.ConversationGroup}, 10)
	if findConv(chats, first.ID) != nil {
		t.Error("AI thread leaked into the Chats tab")
	}
	kautilya, _ := r.Inbox(ctx, a, []string{model.ConversationAI}, 10)
	if findConv(kautilya, first.ID) == nil {
		t.Error("AI thread missing from the Kautilya tab")
	}
}

func findConv(items []model.InboxItem, id string) *model.InboxItem {
	for i := range items {
		if items[i].ID == id {
			return &items[i]
		}
	}
	return nil
}

func seqsOf(msgs []model.Message) []int64 {
	out := make([]int64, len(msgs))
	for i, m := range msgs {
		out[i] = m.Seq
	}
	return out
}

func bodiesOf(msgs []model.Message) []string {
	out := make([]string, len(msgs))
	for i, m := range msgs {
		out[i] = m.Body
	}
	return out
}