package context

import (
	"testing"

	"github.com/edgeai/gateway/internal/config"
	"github.com/edgeai/gateway/pkg/api"
)

func TestTokenEstimator(t *testing.T) {
	est := NewTokenEstimator()

	// Empty string
	if got := est.EstimateText(""); got != 0 {
		t.Errorf("empty string: expected 0, got %d", got)
	}

	// English text
	tokens := est.EstimateText("Hello world, this is a test.")
	if tokens <= 0 {
		t.Errorf("expected positive tokens for English, got %d", tokens)
	}

	// Chinese text (each char ~1 token)
	cjkTokens := est.EstimateText("你好世界")
	if cjkTokens != 4 {
		t.Errorf("expected 4 tokens for 4 CJK chars, got %d", cjkTokens)
	}
}

func TestEstimateKVCache(t *testing.T) {
	// 1000 tokens, 32 layers, 4096 hidden dim, 2 bytes/element
	result := EstimateKVCache(1000, 32, 4096, 2)
	expected := int64(1000) * 32 * 2 * 4096 * 2
	if result != expected {
		t.Errorf("expected %d, got %d", expected, result)
	}
}

func TestAssemblerNoTrim(t *testing.T) {
	cfg := &config.ContextConfig{SafetyMarginRatio: 0.08}
	a := NewAssembler(cfg)

	history := []api.Message{
		{Role: "user", Content: "Hi"},
		{Role: "assistant", Content: "Hello!"},
	}
	newMsgs := []api.Message{
		{Role: "user", Content: "How are you?"},
	}

	result := a.Assemble(history, newMsgs, 1000, 100, "summary_and_recent")
	if result.Trimmed {
		t.Error("expected no trimming for small context")
	}
	if len(result.Messages) != 3 {
		t.Errorf("expected 3 messages, got %d", len(result.Messages))
	}
}

func TestAssemblerTrimRecentOnly(t *testing.T) {
	cfg := &config.ContextConfig{SafetyMarginRatio: 0.08}
	a := NewAssembler(cfg)

	// Create many messages that exceed budget
	msgs := make([]api.Message, 20)
	for i := range msgs {
		msgs[i] = api.Message{Role: "user", Content: "This is message number " + string(rune('A'+i))}
	}

	result := a.Assemble(msgs, []api.Message{}, 50, 10, "recent_only")
	if !result.Trimmed {
		t.Error("expected trimming for large context")
	}
	if len(result.Messages) >= 20 {
		t.Error("expected fewer messages after trimming")
	}
}

func TestAssemblerSummaryAndRecent(t *testing.T) {
	cfg := &config.ContextConfig{SafetyMarginRatio: 0.08}
	a := NewAssembler(cfg)

	msgs := make([]api.Message, 0, 22)
	msgs = append(msgs, api.Message{Role: "system", Content: "You are a helpful assistant."})
	for i := 0; i < 20; i++ {
		msgs = append(msgs, api.Message{Role: "user", Content: "Message " + string(rune('A'+i%26))})
		msgs = append(msgs, api.Message{Role: "assistant", Content: "Response " + string(rune('A'+i%26))})
	}

	result := a.Assemble(msgs, []api.Message{}, 80, 20, "summary_and_recent")
	if !result.Trimmed {
		t.Error("expected trimming")
	}

	// System message should be preserved
	hasSystem := false
	hasSummary := false
	for _, m := range result.Messages {
		if m.Role == "system" {
			if content, ok := m.Content.(string); ok {
				if content == "You are a helpful assistant." {
					hasSystem = true
				}
				if contains(content, "summarized") {
					hasSummary = true
				}
			}
		}
	}
	if !hasSystem {
		t.Error("system message should be preserved")
	}
	if !hasSummary {
		t.Error("summary placeholder should be present when trimmed")
	}
}

func contains(s, substr string) bool {
	return len(s) >= len(substr) && (s == substr || (len(s) > len(substr) && (indexOf(s, substr) >= 0)))
}

func indexOf(s, substr string) int {
	for i := 0; i <= len(s)-len(substr); i++ {
		if s[i:i+len(substr)] == substr {
			return i
		}
	}
	return -1
}