package api

import (
	"context"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"os"
	"testing"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

func newMetricsRouter(h *handlers) chi.Router {
	r := chi.NewRouter()
	r.Get("/api/me/recommendation-metrics", h.handleGetRecommendationMetrics)
	return r
}

// seedSourcedPlay inserts a play_event with an explicit source + completion +
// skip flag. A nil source inserts NULL (manual library play → baseline).
// pickKind is the For You taste/fresh attribution (#1249); nil everywhere
// except attributed for_you plays.
func seedSourcedPlay(
	t *testing.T, h *handlers, userID, trackID, sessionID pgtype.UUID,
	source, pickKind *string, completion float64, skipped bool,
) {
	t.Helper()
	if _, err := h.pool.Exec(context.Background(),
		`INSERT INTO play_events
		   (user_id, track_id, session_id, started_at, source, pick_kind, completion_ratio, was_skipped)
		 VALUES ($1, $2, $3, now(), $4, $5, $6, $7)`,
		userID, trackID, sessionID, source, pickKind, completion, skipped); err != nil {
		t.Fatalf("seed sourced play: %v", err)
	}
}

func TestRecommendationMetrics_NoSession401(t *testing.T) {
	h, _ := testHandlers(t)
	req := httptest.NewRequest(http.MethodGet, "/api/me/recommendation-metrics", nil)
	rec := httptest.NewRecorder()
	newMetricsRouter(h).ServeHTTP(rec, req)
	if rec.Code != http.StatusUnauthorized {
		t.Errorf("status = %d, want 401", rec.Code)
	}
}

// findSurface returns the named family from any group, or nil.
func findSurface(resp recommendationMetricsResp, key string) *surfaceMetric {
	for _, g := range resp.Groups {
		for i := range g.Surfaces {
			if g.Surfaces[i].Key == key {
				return &g.Surfaces[i]
			}
		}
	}
	return nil
}

func TestBucketMetricsResponse_FamiliesGroupsBaseline(t *testing.T) {
	src := func(s string) *string { return &s }
	rows := []dbq.RecommendationSourceMetricsForUserRow{
		{Source: src("for_you"), Plays: 3, Skips: 1, CompletionN: 3, AvgCompletion: 2.0 / 3},
		// Two radio sessions collapse into one "radio" family; weighted
		// completion = (0.2*1 + 0.8*1) / 2 = 0.5.
		{Source: src("radio:aaaa"), Plays: 1, Skips: 1, CompletionN: 1, AvgCompletion: 0.2},
		{Source: src("radio:bbbb"), Plays: 1, Skips: 0, CompletionN: 1, AvgCompletion: 0.8},
		{Source: src("album:cccc"), Plays: 1, Skips: 0, CompletionN: 0, AvgCompletion: 0},
		{Source: src("discover"), Plays: 1, Skips: 0, CompletionN: 1, AvgCompletion: 0.8},
		// NULL source = manual plays → baseline, not a group row.
		{Source: nil, Plays: 25, Skips: 5, CompletionN: 20, AvgCompletion: 0.9},
	}
	resp := bucketMetricsResponse(recMetricsDefaultDays, rows)

	if resp.Baseline == nil {
		t.Fatal("baseline missing")
	}
	if resp.Baseline.Plays != 25 || resp.Baseline.SkipRate != 0.2 {
		t.Errorf("baseline = %+v, want plays=25 skip_rate=0.2", resp.Baseline)
	}
	if resp.Baseline.LowConfidence {
		t.Error("baseline with 25 plays should not be low-confidence")
	}

	radio := findSurface(resp, "radio")
	if radio == nil {
		t.Fatal("radio family missing")
	}
	if radio.Plays != 2 || radio.Skips != 1 {
		t.Errorf("radio plays/skips = %d/%d, want 2/1", radio.Plays, radio.Skips)
	}
	if radio.AvgCompletion < 0.49 || radio.AvgCompletion > 0.51 {
		t.Errorf("radio avg_completion = %.3f, want 0.5 (play-weighted merge)", radio.AvgCompletion)
	}
	if !radio.LowConfidence {
		t.Error("radio with 2 plays should be low-confidence")
	}

	if s := findSurface(resp, "direct_album"); s == nil || s.Plays != 1 {
		t.Errorf("direct_album = %+v, want plays=1", s)
	}
	if s := findSurface(resp, ""); s != nil {
		t.Error("NULL source must not appear as a surface family")
	}

	// No attributed (taste/fresh) plays in this fixture → no breakdown;
	// an all-unattributed breakdown would just repeat the parent row.
	if fy := findSurface(resp, "for_you"); fy == nil || fy.Breakdown != nil {
		t.Errorf("for_you breakdown = %+v, want nil without attributed plays", fy)
	}

	// Group ordering is intent-banded: go_to before discovery before direct.
	wantOrder := []string{intentGoTo, intentDiscovery, intentDirect}
	if len(resp.Groups) != len(wantOrder) {
		t.Fatalf("groups = %d, want %d", len(resp.Groups), len(wantOrder))
	}
	for i, g := range resp.Groups {
		if g.Intent != wantOrder[i] {
			t.Errorf("group[%d].intent = %s, want %s", i, g.Intent, wantOrder[i])
		}
	}
}

func TestBucketMetricsResponse_ForYouBreakdown(t *testing.T) {
	src := func(s string) *string { return &s }
	kind := func(s string) *string { return &s }
	rows := []dbq.RecommendationSourceMetricsForUserRow{
		{Source: src("for_you"), PickKind: kind("taste"), Plays: 30, Skips: 3,
			CompletionN: 30, AvgCompletion: 0.9},
		{Source: src("for_you"), PickKind: kind("fresh"), Plays: 10, Skips: 4,
			CompletionN: 10, AvgCompletion: 0.5},
		// NULL pick_kind = plays that predate attribution.
		{Source: src("for_you"), Plays: 5, Skips: 1, CompletionN: 5, AvgCompletion: 0.7},
	}
	resp := bucketMetricsResponse(recMetricsDefaultDays, rows)

	fy := findSurface(resp, "for_you")
	if fy == nil {
		t.Fatal("for_you family missing")
	}
	// The parent row stays the sum of its breakdown.
	if fy.Plays != 45 || fy.Skips != 8 {
		t.Errorf("for_you plays/skips = %d/%d, want 45/8", fy.Plays, fy.Skips)
	}
	if len(fy.Breakdown) != 3 {
		t.Fatalf("breakdown rows = %d, want 3 (taste, fresh, earlier)", len(fy.Breakdown))
	}
	wantKeys := []string{"for_you_taste", "for_you_fresh", "for_you_unattributed"}
	for i, k := range wantKeys {
		if fy.Breakdown[i].Key != k {
			t.Errorf("breakdown[%d].key = %s, want %s", i, fy.Breakdown[i].Key, k)
		}
	}
	taste, fresh := fy.Breakdown[0], fy.Breakdown[1]
	if taste.Plays != 30 || taste.SkipRate != 0.1 || taste.LowConfidence {
		t.Errorf("taste = %+v, want plays=30 skip_rate=0.1 confident", taste)
	}
	if fresh.Plays != 10 || fresh.SkipRate != 0.4 || !fresh.LowConfidence {
		t.Errorf("fresh = %+v, want plays=10 skip_rate=0.4 low-confidence", fresh)
	}
	// Breakdown rows never appear as their own surface families.
	if s := findSurface(resp, "for_you_taste"); s != nil {
		t.Error("for_you_taste must not be a top-level surface")
	}
}

func TestBucketMetricsResponse_DiscoverBucketBreakdown(t *testing.T) {
	// Provenance is standard (#1270): Discover's bucket stamps surface as
	// a breakdown exactly like For You's taste/fresh — this is what makes
	// the 40/30/30 allocation judgeable instead of a guess.
	src := func(s string) *string { return &s }
	kind := func(s string) *string { return &s }
	rows := []dbq.RecommendationSourceMetricsForUserRow{
		{Source: src("discover"), PickKind: kind("dormant"), Plays: 8, Skips: 2,
			CompletionN: 8, AvgCompletion: 0.8},
		{Source: src("discover"), PickKind: kind("cross_user"), Plays: 6, Skips: 3,
			CompletionN: 6, AvgCompletion: 0.6},
		{Source: src("discover"), PickKind: kind("random"), Plays: 4, Skips: 3,
			CompletionN: 4, AvgCompletion: 0.4},
		// NULL pick_kind = plays that predate bucket stamping.
		{Source: src("discover"), Plays: 2, Skips: 0, CompletionN: 2, AvgCompletion: 0.9},
	}
	resp := bucketMetricsResponse(recMetricsDefaultDays, rows)

	d := findSurface(resp, "discover")
	if d == nil {
		t.Fatal("discover family missing")
	}
	if d.Plays != 20 || d.Skips != 8 {
		t.Errorf("discover plays/skips = %d/%d, want 20/8", d.Plays, d.Skips)
	}
	wantKeys := []string{
		"discover_dormant", "discover_cross_user", "discover_random",
		"discover_unattributed",
	}
	if len(d.Breakdown) != len(wantKeys) {
		t.Fatalf("breakdown rows = %d, want %d", len(d.Breakdown), len(wantKeys))
	}
	for i, k := range wantKeys {
		if d.Breakdown[i].Key != k {
			t.Errorf("breakdown[%d].key = %s, want %s", i, d.Breakdown[i].Key, k)
		}
	}
	if b := d.Breakdown[0]; b.Label != "Dormant artists" || b.Plays != 8 {
		t.Errorf("dormant row = %+v, want label=Dormant artists plays=8", b)
	}
}

func TestRecommendationMetrics_BucketsWithBaseline(t *testing.T) {
	if os.Getenv("MINSTREL_TEST_DATABASE_URL") == "" {
		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
	}
	h, pool := testHandlers(t)
	user := seedUser(t, pool, "metrics", "pw", false)
	artist := seedArtist(t, pool, "MetricArtist")
	album := seedAlbum(t, pool, artist.ID, "MetricAlbum", 2020)
	tk := seedTrack(t, pool, album.ID, artist.ID, "MetricTrack", 1, 200000)
	session := seedPlaySession(t, pool, user.ID, time.Now())

	forYou := "for_you"
	radioA := "radio:11111111-1111-1111-1111-111111111111"
	taste, fresh := "taste", "fresh"
	// for_you: 3 plays, 1 skipped; completions 1.0, 0.95, 0.05 → mean 0.6667.
	// Two attributed as taste picks, the skipped one as a fresh pick (#1249).
	seedSourcedPlay(t, h, user.ID, tk.ID, session, &forYou, &taste, 1.0, false)
	seedSourcedPlay(t, h, user.ID, tk.ID, session, &forYou, &taste, 0.95, false)
	seedSourcedPlay(t, h, user.ID, tk.ID, session, &forYou, &fresh, 0.05, true)
	// A radio session play collapses into the "radio" family.
	seedSourcedPlay(t, h, user.ID, tk.ID, session, &radioA, nil, 0.8, false)
	// Manual play (NULL source) — the baseline row.
	seedSourcedPlay(t, h, user.ID, tk.ID, session, nil, nil, 1.0, false)

	req := httptest.NewRequest(http.MethodGet, "/api/me/recommendation-metrics", nil)
	req = withUser(req, user)
	rec := httptest.NewRecorder()
	newMetricsRouter(h).ServeHTTP(rec, req)
	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want 200", rec.Code)
	}

	var resp recommendationMetricsResp
	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if resp.WindowDays != recMetricsDefaultDays {
		t.Errorf("window_days = %d, want %d", resp.WindowDays, recMetricsDefaultDays)
	}
	if resp.Baseline == nil || resp.Baseline.Plays != 1 {
		t.Fatalf("baseline = %+v, want plays=1", resp.Baseline)
	}
	fy := findSurface(resp, "for_you")
	if fy == nil {
		t.Fatal("for_you metrics missing")
	}
	if fy.Plays != 3 || fy.Skips != 1 {
		t.Errorf("for_you plays/skips = %d/%d, want 3/1", fy.Plays, fy.Skips)
	}
	if fy.SkipRate < 0.32 || fy.SkipRate > 0.34 {
		t.Errorf("for_you skip_rate = %.3f, want ~0.333", fy.SkipRate)
	}
	if fy.AvgCompletion < 0.66 || fy.AvgCompletion > 0.67 {
		t.Errorf("for_you avg_completion = %.4f, want ~0.6667", fy.AvgCompletion)
	}
	// Pick-kind attribution surfaces as the For You breakdown (#1249).
	if len(fy.Breakdown) != 2 {
		t.Fatalf("for_you breakdown rows = %d, want 2 (taste, fresh)", len(fy.Breakdown))
	}
	if b := fy.Breakdown[0]; b.Key != "for_you_taste" || b.Plays != 2 || b.Skips != 0 {
		t.Errorf("breakdown[0] = %+v, want for_you_taste plays=2 skips=0", b)
	}
	if b := fy.Breakdown[1]; b.Key != "for_you_fresh" || b.Plays != 1 || b.Skips != 1 {
		t.Errorf("breakdown[1] = %+v, want for_you_fresh plays=1 skips=1", b)
	}
	if radio := findSurface(resp, "radio"); radio == nil || radio.Plays != 1 {
		t.Errorf("radio family = %+v, want plays=1 (collapsed from radio:<uuid>)", radio)
	}
}