// These tests translate docs/use-cases/ai_routing.feature. They drive the
// Summarizer through a FAKE Completer — never the live LiteLLM gateway — and the
// load-bearing assertion is the local-first guarantee: when no BYO provider is
// configured, the transcript content reaches the local stack and nowhere else.
package summarizer

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

	"gitea.d-ma.be/mathias/tapir/internal/domain"
	"gitea.d-ma.be/mathias/tapir/internal/ports"
)

// compile-time check: Summarizer satisfies the port.
var _ ports.Summarizer = (*Summarizer)(nil)

// fakeClient records every prompt it is asked to complete, so a test can prove
// whether content reached it. It returns reply, or err when err != nil.
type fakeClient struct {
	reply    string
	err      error
	calls    int
	lastUser string
}

func (f *fakeClient) Complete(_ context.Context, _, user string) (string, error) {
	f.calls++
	f.lastUser = user
	if f.err != nil {
		return "", f.err
	}
	return f.reply, nil
}

const goodReply = `{"summary":"A talk about Go.","highlights":["ports and adapters"],"takeaways":["copy, don't couple"]}`

func testVideo() domain.Video {
	return domain.Video{ID: "vid-1", UserID: "user-1", Title: "Clean Architecture in Go", URL: "https://x/y"}
}

func testTranscript() domain.Transcript {
	return domain.Transcript{VideoID: "vid-1", UserID: "user-1", Source: domain.SourceCaptions, Content: "secret confidential transcript body"}
}

// Scenario: Local AI produces the summary.
func TestSummarize_LocalSucceeds(t *testing.T) {
	local := &fakeClient{reply: goodReply}
	byo := &fakeClient{reply: `{"summary":"should not be used"}`}
	s := New(
		Endpoint{Client: local, Provider: "local", Model: "iguana/deepseek-r1-14b"},
		&Endpoint{Client: byo, Provider: "anthropic", Model: "claude"},
	)

	sum, err := s.Summarize(context.Background(), testVideo(), testTranscript())
	if err != nil {
		t.Fatalf("Summarize: %v", err)
	}
	if sum.AIProvider != "local" {
		t.Errorf("AIProvider = %q, want local", sum.AIProvider)
	}
	if sum.AIModel != "iguana/deepseek-r1-14b" {
		t.Errorf("AIModel = %q", sum.AIModel)
	}
	if sum.FallbackUsed {
		t.Error("FallbackUsed = true, want false")
	}
	if byo.calls != 0 {
		t.Errorf("BYO called %d times; must not be touched when local succeeds", byo.calls)
	}
	if sum.Summary == "" || len(sum.Highlights) != 1 || len(sum.Takeaways) != 1 {
		t.Errorf("parsed summary wrong: %+v", sum)
	}
}

// Scenario: Local AI fails and the user has a BYO provider configured.
func TestSummarize_FallsBackToBYO(t *testing.T) {
	local := &fakeClient{err: errors.New("connection refused")}
	byo := &fakeClient{reply: goodReply}
	s := New(
		Endpoint{Client: local, Provider: "local", Model: "iguana/deepseek-r1-14b"},
		&Endpoint{Client: byo, Provider: "anthropic", Model: "claude-opus"},
	)

	sum, err := s.Summarize(context.Background(), testVideo(), testTranscript())
	if err != nil {
		t.Fatalf("Summarize: %v", err)
	}
	if sum.AIProvider != "anthropic" {
		t.Errorf("AIProvider = %q, want anthropic", sum.AIProvider)
	}
	if sum.AIModel != "claude-opus" {
		t.Errorf("AIModel = %q, want claude-opus", sum.AIModel)
	}
	if !sum.FallbackUsed {
		t.Error("FallbackUsed = false, want true")
	}
	if local.calls != 1 || byo.calls != 1 {
		t.Errorf("calls: local=%d byo=%d, want 1 and 1", local.calls, byo.calls)
	}
}

// Scenario: Local AI fails and the user has no BYO provider.
// AND: my content is not sent to any third-party model.
func TestSummarize_LocalFailsNoBYO_NoExternalSend(t *testing.T) {
	local := &fakeClient{err: errors.New("connection refused")}
	s := New(Endpoint{Client: local, Provider: "local", Model: "iguana/deepseek-r1-14b"}, nil)

	_, err := s.Summarize(context.Background(), testVideo(), testTranscript())
	if err == nil {
		t.Fatal("want error when local fails and no BYO, got nil")
	}
	// Local was the only place content could go; with nil fallback there is no
	// external client to receive it at all. Local saw the content once.
	if local.calls != 1 {
		t.Errorf("local calls = %d, want 1", local.calls)
	}
	if !strings.Contains(local.lastUser, "secret confidential transcript body") {
		t.Error("transcript content should have reached the local stack")
	}
}

// Scenario: A user without BYO never has content sent externally — even across
// repeated summarizations. Asserted structurally: a nil fallback means no
// external endpoint exists, so content cannot leave the local stack.
func TestSummarize_NoBYO_ContentOnlyLocal(t *testing.T) {
	local := &fakeClient{reply: goodReply}
	s := New(Endpoint{Client: local, Provider: "local", Model: "iguana/deepseek-r1-14b"}, nil)

	if len(s.endpoints) != 1 {
		t.Fatalf("no BYO configured but chain has %d endpoints, want 1", len(s.endpoints))
	}
	for i := 0; i < 3; i++ {
		sum, err := s.Summarize(context.Background(), testVideo(), testTranscript())
		if err != nil {
			t.Fatalf("Summarize: %v", err)
		}
		if sum.AIProvider != "local" || sum.FallbackUsed {
			t.Errorf("provider=%q fallbackUsed=%v, want local/false", sum.AIProvider, sum.FallbackUsed)
		}
	}
	if local.calls != 3 {
		t.Errorf("local calls = %d, want 3", local.calls)
	}
}

func TestSummarize_EmptyTranscriptIsError(t *testing.T) {
	local := &fakeClient{reply: goodReply}
	s := New(Endpoint{Client: local, Provider: "local", Model: "m"}, nil)

	none := domain.Transcript{VideoID: "vid-1", Source: domain.SourceNone}
	if _, err := s.Summarize(context.Background(), testVideo(), none); err == nil {
		t.Fatal("want error for transcript with no text")
	}
	if local.calls != 0 {
		t.Errorf("local called %d times for empty transcript; must not call the model", local.calls)
	}
}

// parse tolerates thinking-model wrapping (reasoning + code fences around JSON).
func TestParse_ToleratesFencedThinkingOutput(t *testing.T) {
	raw := "<think>let me reason...</think>\n```json\n" + goodReply + "\n```"
	p, err := parse(raw)
	if err != nil {
		t.Fatalf("parse: %v", err)
	}
	if p.Summary != "A talk about Go." {
		t.Errorf("summary = %q", p.Summary)
	}
}

func TestParse_EmptySummaryRejected(t *testing.T) {
	if _, err := parse(`{"summary":"  ","highlights":[]}`); err == nil {
		t.Fatal("want error for empty summary (thinking model returned no content)")
	}
}

// parse tolerates a small model emitting "highlights" as a bare string instead
// of an array — the production koala/phi4-mini quirk that errored with
// "cannot unmarshal string into Go struct field ... highlights of type []string".
func TestParse_ToleratesStringHighlights(t *testing.T) {
	p, err := parse(`{"summary":"s","highlights":"one big point","takeaways":["a","b"]}`)
	if err != nil {
		t.Fatalf("parse: %v", err)
	}
	if len(p.Highlights) != 1 || p.Highlights[0] != "one big point" {
		t.Errorf("highlights = %v, want [\"one big point\"]", p.Highlights)
	}
	if len(p.Takeaways) != 2 {
		t.Errorf("takeaways = %v, want 2", p.Takeaways)
	}
}

// Chain: an endpoint that returns a 200 with unparseable output is treated as a
// failure, and the next endpoint in the chain is tried. This is the case the old
// primary->fallback shape missed — a parse error short-circuited instead of
// falling back.
func TestSummarize_FallsBackOnMalformedOutput(t *testing.T) {
	bad := &fakeClient{reply: `{"summary": not json`}
	good := &fakeClient{reply: goodReply}
	s := NewChain([]Endpoint{
		{Client: bad, Provider: "local", Model: "koala/phi4-mini"},
		{Client: good, Provider: "local", Model: "koala/phi4-14b"},
	}, 0)

	sum, err := s.Summarize(context.Background(), testVideo(), testTranscript())
	if err != nil {
		t.Fatalf("Summarize: %v", err)
	}
	if sum.AIModel != "koala/phi4-14b" {
		t.Errorf("AIModel = %q, want koala/phi4-14b (fell back past malformed primary)", sum.AIModel)
	}
	if !sum.FallbackUsed {
		t.Error("FallbackUsed = false, want true")
	}
	if bad.calls != 1 || good.calls != 1 {
		t.Errorf("calls: bad=%d good=%d, want 1 and 1", bad.calls, good.calls)
	}
}

// Chain: when every endpoint fails, no summary is produced and the joined error
// names each failure so the engine queues the work for retry.
func TestSummarize_ChainAllEndpointsFail(t *testing.T) {
	a := &fakeClient{err: errors.New("context overflow")}
	b := &fakeClient{reply: "not even json"}
	s := NewChain([]Endpoint{
		{Client: a, Provider: "local", Model: "m1"},
		{Client: b, Provider: "berget", Model: "m2"},
	}, 0)

	if _, err := s.Summarize(context.Background(), testVideo(), testTranscript()); err == nil {
		t.Fatal("want error when all endpoints fail")
	}
	if a.calls != 1 || b.calls != 1 {
		t.Errorf("calls: a=%d b=%d, want 1 and 1", a.calls, b.calls)
	}
}

// A transcript longer than the chain's input budget is truncated before it
// reaches any model, so a small-context primary does not overflow its window.
func TestSummarize_TruncatesLongTranscript(t *testing.T) {
	local := &fakeClient{reply: goodReply}
	const budget = 100
	s := NewChain([]Endpoint{{Client: local, Provider: "local", Model: "m"}}, budget)

	long := domain.Transcript{
		VideoID: "vid-1", UserID: "user-1", Source: domain.SourceCaptions,
		Content: strings.Repeat("word ", 1000), // 5000 bytes, well over budget
	}
	if _, err := s.Summarize(context.Background(), testVideo(), long); err != nil {
		t.Fatalf("Summarize: %v", err)
	}
	// The prompt carries title/URL framing plus the truncation marker, so allow
	// headroom over the raw transcript budget — but it must be far below 5000.
	if len(local.lastUser) > budget+300 {
		t.Errorf("prompt length = %d, want <= %d (transcript not truncated)", len(local.lastUser), budget+300)
	}
	if !strings.Contains(local.lastUser, "truncated") {
		t.Error("truncation marker missing from prompt")
	}
}

func TestNewChain_PanicsOnEmptyChain(t *testing.T) {
	defer func() {
		if recover() == nil {
			t.Fatal("want panic on empty endpoint chain")
		}
	}()
	NewChain(nil, 0)
}