package usecase

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"testing"

	"apps/backend/internal/module/radar/domain"
	"apps/backend/internal/module/radar/repository"
	usageDomain "apps/backend/internal/module/usage/domain"
	usageRepo "apps/backend/internal/module/usage/repository"
	usageUC "apps/backend/internal/module/usage/usecase"
)

type stubAI struct {
	reply      string
	err        error
	lastPrompt string
	calls      int
}

func (s *stubAI) Complete(_ context.Context, _, _, prompt string) (string, error) {
	s.calls++
	s.lastPrompt = prompt
	return s.reply, s.err
}

func (s *stubAI) CompleteStream(ctx context.Context, apiKey, model, prompt string, _ func(string) error) (string, error) {
	return s.Complete(ctx, apiKey, model, prompt)
}

func (s *stubAI) ListModels(context.Context, string) ([]string, error) { return nil, nil }

type stubPainTerms struct {
	terms []string
	err   error
}

func (s stubPainTerms) PainTerms(context.Context, int64) ([]string, error) {
	return s.terms, s.err
}

// platformUsage 給一個用平台點數的會員，這樣扣點與退點都真的會落到用量帳上。
func platformUsage(uid int64) *usageUC.Service {
	key := func(meter string) string { return fmt.Sprintf("%d:%s", uid, meter) }
	return usageUC.New(usageRepo.NewMemory(), &usageUC.StaticResolver{Map: map[string]string{
		key(usageDomain.MeterAICopy):     usageDomain.KeyModePlatform,
		key(usageDomain.MeterAIResearch): usageDomain.KeyModePlatform,
	}})
}

func suggestService(t *testing.T, reply string) (*Service, *stubAI, context.Context) {
	t.Helper()
	ai := &stubAI{reply: reply}
	svc := New(repository.NewMemory())
	svc.AI = ai
	ctx := context.Background()
	if _, err := svc.UpsertServiceProfile(ctx, 42, sampleProfile()); err != nil {
		t.Fatalf("seed profile: %v", err)
	}
	return svc, ai, ctx
}

const suggestReply = `[
  {"term":"台北 婚攝 推薦","reason":"直接在找婚禮攝影的人常這樣問","usage":"include"},
  {"term":"婚禮 攝影 價格","reason":"問價格通常已經在比較廠商","usage":"include"},
  {"term":"徵 婚攝","reason":"這是同業徵才不是客戶需求","usage":"exclude"}
]`

// RW-03：有服務檔案就回得出建議，每則都要有理由。
func TestSuggestWatchTermsReturnsReasonedSuggestions(t *testing.T) {
	svc, ai, ctx := suggestService(t, suggestReply)

	list, err := svc.SuggestWatchTerms(ctx, 42, 0)
	if err != nil {
		t.Fatalf("suggest: %v", err)
	}
	if len(list) != 3 {
		t.Fatalf("got %d suggestions, want 3", len(list))
	}
	for _, s := range list {
		if strings.TrimSpace(s.Reason) == "" {
			t.Fatalf("suggestion %q has no reason", s.Term)
		}
		if s.Usage != domain.SuggestUsageInclude && s.Usage != domain.SuggestUsageExclude {
			t.Fatalf("suggestion %q has usage %q", s.Term, s.Usage)
		}
	}
	if list[2].Usage != domain.SuggestUsageExclude {
		t.Fatalf("exclude suggestion lost its usage: %+v", list[2])
	}

	// prompt 必須帶上服務檔案的內容，否則建議跟這個人的生意無關。
	if !strings.Contains(ai.lastPrompt, "婚禮攝影") {
		t.Fatal("prompt missing the member's service items")
	}
	if !strings.Contains(ai.lastPrompt, "臺北市") {
		t.Fatal("prompt missing the member's service areas")
	}
	if !strings.Contains(ai.lastPrompt, "保證接到案") {
		t.Fatal("prompt missing the forbidden words")
	}
}

func TestSuggestDoesNotCreateWatches(t *testing.T) {
	svc, _, ctx := suggestService(t, suggestReply)

	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err != nil {
		t.Fatalf("suggest: %v", err)
	}
	_, total, err := svc.ListWatches(ctx, 42, domain.WatchListFilter{})
	if err != nil {
		t.Fatalf("list: %v", err)
	}
	if total != 0 {
		t.Fatalf("suggest created %d watches; it must only propose", total)
	}
}

// 沒有服務檔案就沒有依據，寧可明確拒絕也不要憑空猜關鍵字。
func TestSuggestRequiresServiceProfile(t *testing.T) {
	svc := New(repository.NewMemory())
	ai := &stubAI{reply: suggestReply}
	svc.AI = ai

	_, err := svc.SuggestWatchTerms(context.Background(), 42, 0)
	if !errors.Is(err, domain.ErrValidation) {
		t.Fatalf("err = %v, want ErrValidation", err)
	}
	if !strings.Contains(err.Error(), "service-profile") {
		t.Fatalf("error must point at the service profile, got %q", err)
	}
	if ai.calls != 0 {
		t.Fatal("AI was called without a service profile")
	}
}

func TestSuggestRespectsLimit(t *testing.T) {
	svc, ai, ctx := suggestService(t, suggestReply)

	list, err := svc.SuggestWatchTerms(ctx, 42, 2)
	if err != nil {
		t.Fatalf("suggest: %v", err)
	}
	if len(list) != 2 {
		t.Fatalf("got %d suggestions, want the requested 2", len(list))
	}
	if !strings.Contains(ai.lastPrompt, "最多 2 則") {
		t.Fatal("limit was not passed to the prompt")
	}

	if _, err := svc.SuggestWatchTerms(ctx, 42, 999); err != nil {
		t.Fatalf("oversized limit should clamp, not fail: %v", err)
	}
	if !strings.Contains(ai.lastPrompt, "最多 20 則") {
		t.Fatalf("limit was not clamped to %d", domain.MaxSuggestions)
	}
}

func TestSuggestDropsUnusableItems(t *testing.T) {
	// 沒理由、太短、重複的項目都要丟掉，而不是補一句假理由湊數。
	svc, _, ctx := suggestService(t, `[
	  {"term":"婚攝 推薦","reason":"在找攝影師的人常這樣問","usage":"include"},
	  {"term":"沒有理由的詞","reason":"  ","usage":"include"},
	  {"term":"a","reason":"太短","usage":"include"},
	  {"term":"婚攝 推薦","reason":"重複","usage":"include"}
	]`)

	list, err := svc.SuggestWatchTerms(ctx, 42, 0)
	if err != nil {
		t.Fatalf("suggest: %v", err)
	}
	if len(list) != 1 || list[0].Term != "婚攝 推薦" {
		t.Fatalf("got %+v, want only the one usable suggestion", list)
	}
}

// 模型愛加開場白或 code fence，這種回應也要吃得下。
func TestSuggestToleratesProseAroundJSON(t *testing.T) {
	svc, _, ctx := suggestService(t, "好的，以下是建議：\n```json\n"+suggestReply+"\n```\n希望有幫助！")

	list, err := svc.SuggestWatchTerms(ctx, 42, 0)
	if err != nil {
		t.Fatalf("suggest: %v", err)
	}
	if len(list) != 3 {
		t.Fatalf("got %d suggestions from a fenced reply, want 3", len(list))
	}
}

// 解析不出任何東西時要報錯：空清單會被讀成「你的服務沒有關鍵字可監控」。
func TestSuggestFailsLoudlyOnUnusableReply(t *testing.T) {
	svc, _, ctx := suggestService(t, "我不知道要建議什麼")

	_, err := svc.SuggestWatchTerms(ctx, 42, 0)
	if !errors.Is(err, domain.ErrValidation) {
		t.Fatalf("err = %v, want ErrValidation", err)
	}
}

func TestSuggestSurfacesAIFailure(t *testing.T) {
	svc, ai, ctx := suggestService(t, "")
	ai.err = errors.New("provider down")

	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err == nil {
		t.Fatal("AI failure was swallowed")
	}
}

func TestSuggestUsesPainTermsAsMaterialWhenAvailable(t *testing.T) {
	svc, ai, ctx := suggestService(t, suggestReply)
	svc.PainTerms = stubPainTerms{terms: []string{"找不到有檔期的攝影師"}}

	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err != nil {
		t.Fatalf("suggest: %v", err)
	}
	if !strings.Contains(ai.lastPrompt, "找不到有檔期的攝影師") {
		t.Fatal("existing pain terms were not used as prompt material")
	}

	// 素材拿不到只影響品質，不該讓整個請求失敗。
	svc.PainTerms = stubPainTerms{err: errors.New("scout unavailable")}
	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err != nil {
		t.Fatalf("pain term failure must not break suggest: %v", err)
	}
}

/*
計費對照（spec §5.5）：走既有 ai_copy meter，source 標 radar.suggest。

source 前綴是 P1 價格校準的唯一資料來源，標錯就等於這次雷達的成本無法歸因。
*/
func TestSuggestRecordsAiCopyUsageWithRadarSource(t *testing.T) {
	svc, _, ctx := suggestService(t, suggestReply)
	usage := platformUsage(42)
	svc.Usage = usage

	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err != nil {
		t.Fatalf("suggest: %v", err)
	}

	events, err := usage.ListEvents(ctx, 42, usageDomain.CurrentMonthKey(), "all", 0)
	if err != nil {
		t.Fatalf("list events: %v", err)
	}
	if len(events) != 1 {
		t.Fatalf("got %d usage events, want exactly 1", len(events))
	}
	if events[0].Meter != usageDomain.MeterAICopy {
		t.Fatalf("meter = %q, want %q", events[0].Meter, usageDomain.MeterAICopy)
	}
	if events[0].Source != "radar.suggest" {
		t.Fatalf("source = %q, want radar.suggest", events[0].Source)
	}
}

// AI 失敗要退點：扣了點卻沒拿到東西是最難解釋的帳。
func TestSuggestReleasesCreditWhenAIFails(t *testing.T) {
	svc, ai, ctx := suggestService(t, "")
	ai.err = errors.New("provider down")
	usage := platformUsage(42)
	svc.Usage = usage

	if _, err := svc.SuggestWatchTerms(ctx, 42, 0); err == nil {
		t.Fatal("AI failure was swallowed")
	}
	events, err := usage.ListEvents(ctx, 42, usageDomain.CurrentMonthKey(), "all", 0)
	if err != nil {
		t.Fatalf("list events: %v", err)
	}
	if len(events) != 0 {
		t.Fatalf("charged %d events for a failed call", len(events))
	}
}

func TestSuggestWithoutAIClientAsksForKey(t *testing.T) {
	svc := New(repository.NewMemory())
	ctx := context.Background()
	if _, err := svc.UpsertServiceProfile(ctx, 42, sampleProfile()); err != nil {
		t.Fatalf("seed profile: %v", err)
	}

	_, err := svc.SuggestWatchTerms(ctx, 42, 0)
	if !errors.Is(err, domain.ErrValidation) {
		t.Fatalf("err = %v, want ErrValidation pointing at the AI key", err)
	}
}