package cost

import "testing"

func TestParseUsageOpenAI(t *testing.T) {
	payload := []byte(`{
		"usage": {
			"prompt_tokens": 1200,
			"completion_tokens": 340,
			"total_tokens": 1540,
			"prompt_tokens_details": {"cached_tokens": 800},
			"completion_tokens_details": {"reasoning_tokens": 50}
		}
	}`)
	u := ParseUsage(payload)
	if u.PromptTokens != 1200 || u.CompletionTokens != 340 {
		t.Fatalf("unexpected tokens: %+v", u)
	}
	if u.CachedInputTokens != 800 || u.ReasoningTokens != 50 {
		t.Fatalf("unexpected details: %+v", u)
	}
}

func TestParseUsageFallback(t *testing.T) {
	u := ParseUsage([]byte(`{"choices":[]}`))
	if u.TotalTokens != 1 {
		t.Fatalf("expected fallback 1, got %d", u.TotalTokens)
	}
}

func TestComputeCostMicroEUR(t *testing.T) {
	price := ModelPrice{
		InputMicroEURPerMTok:  1_000_000,
		OutputMicroEURPerMTok: 2_000_000,
	}
	usage := UsageDetail{
		PromptTokens:     1000,
		CompletionTokens: 500,
		CachedInputTokens: 200,
		TotalTokens:      1500,
	}
	cost, estimated := ComputeCostMicroEUR(usage, price, true)
	if estimated {
		t.Fatal("should not be estimated when price found")
	}
	// uncached 800 * 1 + cached 200 * 0.5 + output 500 * 2 = 800+100+1000 = 1900 micro (cached uses half input)
	if cost < 1800 || cost > 2000 {
		t.Fatalf("unexpected cost %d", cost)
	}
}

func TestComputeCostUnknownModel(t *testing.T) {
	usage := UsageDetail{TotalTokens: 1_000_000}
	cost, estimated := ComputeCostMicroEUR(usage, ModelPrice{}, false)
	if !estimated {
		t.Fatal("expected estimated")
	}
	if cost != fallbackInputMicroEURPerMTok {
		t.Fatalf("expected fallback cost %d, got %d", fallbackInputMicroEURPerMTok, cost)
	}
}

func TestMergeStreamUsage(t *testing.T) {
	acc := UsageDetail{}
	chunk1 := []byte(`{"usage":{"prompt_tokens":10,"completion_tokens":0,"total_tokens":10}}`)
	chunk2 := []byte(`{"usage":{"prompt_tokens":100,"completion_tokens":40,"total_tokens":140}}`)
	acc = MergeStreamUsage(acc, chunk1)
	acc = MergeStreamUsage(acc, chunk2)
	if acc.TotalTokens != 140 {
		t.Fatalf("expected 140, got %d", acc.TotalTokens)
	}
}