package agent

import (
	"context"
	"fmt"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"ollie/cmd/olliesrv/internal/backend"
	olog "ollie/log"
)

// noOpLogger is a logger that discards all output.
var noOpLogger = olog.NewWriter("test", olog.LevelError+1, nil, nil)

// blockingBackend implements backend.Backend but blocks on ChatStream until ctx is cancelled.
type blockingBackend struct {
	chatStreamBlocked atomic.Bool
	model             string
	ctxLength         int
}

func (b *blockingBackend) ChatStream(ctx context.Context, messages []backend.Message, tools []backend.Tool, params backend.GenerationParams) (<-chan backend.StreamEvent, error) {
	b.chatStreamBlocked.Store(true)
	ch := make(chan backend.StreamEvent, 1)
	go func() {
		defer close(ch)
		select {
		case <-ctx.Done():
			return
		}
	}()
	return ch, nil
}
func (b *blockingBackend) Name() string                        { return "test" }
func (b *blockingBackend) DefaultModel() string                { return "test-model" }
func (b *blockingBackend) Model() string                       { return b.model }
func (b *blockingBackend) SetModel(model string)               { b.model = model }
func (b *blockingBackend) ContextLength(_ context.Context) int { return b.ctxLength }
func (b *blockingBackend) Models(_ context.Context) []string   { return []string{"test-model"} }

// TestStripColdCancellation verifies that /stop (Interrupt) cancels stripCold's
// blocking LLM call promptly instead of waiting for it to complete.
func TestStripColdCancellation(t *testing.T) {
	b := &blockingBackend{model: "test", ctxLength: 128000}
	h := newHistory("test input")

	// Add enough messages so stripCold has work to do.
	// stripCold processes messages before index len(messages)-hotTailSize (8).
	// Need >8 cold-zone tool results (>200 chars each).
	for i := 0; i < 10; i++ {
		h.messages = append(h.messages, backend.Message{
			Role:    "tool",
			Content: fmt.Sprintf("tool-%d: %s", i, strings.Repeat("x", 300)),
		})
	}

	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan struct{})

	go func() {
		h.stripCold(ctx, b)
		close(done)
	}()

	// Wait for the backend to be blocked.
	timeout := time.After(2 * time.Second)
	for !b.chatStreamBlocked.Load() {
		select {
		case <-done:
			t.Fatal("stripCold exited before backend was blocked")
		case <-timeout:
			t.Fatal("timed out waiting for backend to block")
		case <-time.After(10 * time.Millisecond):
		}
	}

	// Cancel via the same mechanism as Interrupt — this should unblock stripCold.
	cancel()

	select {
	case <-done:
		// Good — stripCold returned promptly after cancellation.
	case <-time.After(1 * time.Second):
		t.Fatal("stripCold did not return within 1s of context cancellation")
	}
}

// TestPreRunCompactionCancellation verifies that /stop cancels pre-run auto-compaction
// which uses runCompact → history.compact → ChatStream.
func TestPreRunCompactionCancellation(t *testing.T) {
	b := &blockingBackend{model: "test", ctxLength: 128000}

	// Create an agent with enough history to trigger compaction (>hotTailSize+warmIndexSize=18).
	ag := &Agent{
		runtime: &Runtime{
			Backend: b,
		},
		history: newHistory("test"),
		log: noOpLogger,
	}

	// Add enough messages to exceed the compact threshold.
	for i := 0; i < 30; i++ {
		ag.history.appendUserMessage(strings.Repeat("x", 500))
	}

	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan struct{})

	go func() {
		_, err := ag.runCompact(ctx, "test")
		if err != nil && !strings.Contains(err.Error(), "auto-compact") {
			t.Logf("runCompact error (expected): %v", err)
		}
		close(done)
	}()

	// Wait for the backend to be blocked.
	timeout := time.After(2 * time.Second)
	for !b.chatStreamBlocked.Load() {
		select {
		case <-done:
			t.Fatal("runCompact exited before backend was blocked")
		case <-timeout:
			t.Fatal("timed out waiting for backend to block")
		case <-time.After(10 * time.Millisecond):
		}
	}

	// Cancel — this should unblock the compaction.
	cancel()

	select {
	case <-done:
		// Good — runCompact returned promptly after cancellation.
	case <-time.After(1 * time.Second):
		t.Fatal("runCompact did not return within 1s of context cancellation")
	}
}