package gateway

import (
	"testing"

	"llmsproxy/internal/types"
)

// TestRecordChatUsageKeepsReasoningTokens pins the reasoning-token plumbing.
//
// The adapters already parse completion_tokens_details.reasoning_tokens and
// forward it (opencodego, gemini, anthropic all do), and types.go has carried
// the field since it was defined — but nothing ever READ it. The number arrived
// in the response and was discarded at the one place that could have kept it,
// so a pricing rule had no way to split thinking from output.
//
// The property that matters most: reasoning is a SUBSET of completion. Every
// provider measured bills it at the completion rate, so a billing plugin that
// added it to completion_tokens would double-charge every thinking token. The
// test asserts completion is left alone.
func TestRecordChatUsageKeepsReasoningTokens(t *testing.T) {
	rec := &Req{}
	resp := &types.UnifiedResponse{
		TokenUsage: types.TokenUsage{
			Prompt:     100,
			Completion: 500,
			CompletionTokensDetails: &types.CompletionTokensDetails{
				ReasoningTokens: 320,
			},
		},
	}
	recordChatUsage(rec, &types.ChatRequest{}, resp)

	if rec.Reasoning != 320 {
		t.Errorf("Reasoning = %d, want 320", rec.Reasoning)
	}
	// The subset must not be folded into completion — it is already counted there.
	if rec.Compl != 500 {
		t.Errorf("Compl = %d, want 500 (reasoning is a subset, never additive)", rec.Compl)
	}
	if rec.Prompt != 100 {
		t.Errorf("Prompt = %d, want 100", rec.Prompt)
	}
}

// TestRecordChatUsageReasoningAbsentStaysZero: "not reported" and "reported as
// zero" must both leave the field at 0, and neither may invent a number. A
// plugin reading Reasoning cannot tell them apart, which is why the field is
// documented as "0 means not reported" rather than "0 means no thinking".
func TestRecordChatUsageReasoningAbsentStaysZero(t *testing.T) {
	for _, tc := range []struct {
		name string
		u    types.TokenUsage
	}{
		{"no details object", types.TokenUsage{Prompt: 10, Completion: 20}},
		{"details without reasoning", types.TokenUsage{
			Prompt:                  10,
			Completion:              20,
			CompletionTokensDetails: &types.CompletionTokensDetails{},
		}},
	} {
		rec := &Req{}
		recordChatUsage(rec, &types.ChatRequest{}, &types.UnifiedResponse{TokenUsage: tc.u})
		if rec.Reasoning != 0 {
			t.Errorf("%s: Reasoning = %d, want 0", tc.name, rec.Reasoning)
		}
		if rec.Compl != 20 {
			t.Errorf("%s: Compl = %d, want 20", tc.name, rec.Compl)
		}
	}
}