package tasksboard

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"sync"
	"time"

	"l-ai-agent-kaya/internal/inference"
	"l-ai-agent-kaya/internal/profile"
	"l-ai-agent-kaya/internal/tasksws"
)

const agentID = "kaya"

// Loop listens to Tasks board WS and replies to @kaya mentions.
type Loop struct {
	WSURL           string
	Token           string
	REST            *Client
	Core            inference.Runner
	Profile         profile.Profile
	Model           string
	ResponseTimeout time.Duration
	Log             *slog.Logger

	mu     sync.Mutex
	seen   map[string]struct{}
	seenQ  []string
	maxSeen int
}

func (l *Loop) log() *slog.Logger {
	if l.Log != nil {
		return l.Log
	}
	return slog.Default()
}

// Run blocks until ctx is cancelled.
func (l *Loop) Run(ctx context.Context) {
	if l.seen == nil {
		l.seen = map[string]struct{}{}
	}
	if l.maxSeen <= 0 {
		l.maxSeen = 4096
	}
	client := &tasksws.Client{
		URL:   l.WSURL,
		Token: l.Token,
		Agent: agentID,
		Log:   l.log(),
		OnEvent: func(ctx context.Context, ev tasksws.Event) error {
			return l.handle(ctx, ev)
		},
	}
	l.log().Info("tasks board loop starting", "ws", l.WSURL, "agent", agentID)
	client.Run(ctx)
}

func (l *Loop) handle(ctx context.Context, ev tasksws.Event) error {
	if ev.Type != "comment.added" {
		return nil
	}
	if ev.Comment == nil || ev.Task == nil {
		return nil
	}
	if !tasksws.MentionsSelf(ev, agentID) {
		return nil
	}
	if strings.EqualFold(ev.Comment.AuthorID, agentID) {
		return nil
	}
	commentID := ev.Comment.ID
	if commentID == "" {
		return nil
	}
	if !l.markSeen(commentID) {
		return nil
	}

	taskID := ev.Task.ID
	l.log().Info("mention reply", "comment_id", commentID, "task_id", taskID, "author", ev.Comment.AuthorID)

	replyCtx, cancel := context.WithTimeout(ctx, l.ResponseTimeout)
	defer cancel()

	task, err := l.REST.GetTask(replyCtx, taskID)
	if err != nil {
		return fmt.Errorf("get task: %w", err)
	}
	comments, err := l.REST.ListComments(replyCtx, taskID)
	if err != nil {
		return fmt.Errorf("list comments: %w", err)
	}

	userPrompt := buildUserPrompt(task, comments, commentID)
	timeoutSec := uint32(l.ResponseTimeout.Seconds())
	if timeoutSec < 30 {
		timeoutSec = 30
	}
	model := l.Model
	if model == "" && l.Profile.LLM.Response.Model != "" {
		model = l.Profile.LLM.Response.Model
	}
	if model == "" {
		model = "deepseek-v4-flash"
	}

	res, err := l.Core.RunAgent(replyCtx, inference.RunRequest{
		Messages: []inference.ChatMessage{
			{Role: "system", Content: l.Profile.SystemPrompt()},
			{Role: "user", Content: userPrompt},
		},
		Model:          model,
		AgentID:        agentID,
		RequestID:      "mention-reply:" + commentID,
		IdempotencyKey: "mention-reply:" + commentID,
		TimeoutSeconds: timeoutSec,
		Metadata:       map[string]string{"trace_reason": "kaya_mention_reply", "comment_id": commentID, "task_id": taskID},
		ToolsEnabled:   false,
	})
	if err != nil {
		return fmt.Errorf("RunAgent: %w", err)
	}
	body := strings.TrimSpace(res.Content)
	if body == "" {
		return fmt.Errorf("empty agent reply for comment %s", commentID)
	}

	_, err = l.REST.PostComment(replyCtx, taskID, body, "mention-reply:"+commentID)
	if err != nil {
		return fmt.Errorf("post comment: %w", err)
	}
	l.log().Info("mention reply posted", "comment_id", commentID, "task_id", taskID, "duration_ms", res.DurationMS)
	return nil
}

func (l *Loop) markSeen(id string) bool {
	l.mu.Lock()
	defer l.mu.Unlock()
	if _, ok := l.seen[id]; ok {
		return false
	}
	l.seen[id] = struct{}{}
	l.seenQ = append(l.seenQ, id)
	for len(l.seenQ) > l.maxSeen {
		old := l.seenQ[0]
		l.seenQ = l.seenQ[1:]
		delete(l.seen, old)
	}
	return true
}

func buildUserPrompt(task Task, comments []Comment, triggerID string) string {
	var b strings.Builder
	b.WriteString("Task context:\n")
	b.WriteString(fmt.Sprintf("- id: %s\n", task.ID))
	b.WriteString(fmt.Sprintf("- title: %s\n", task.Title))
	b.WriteString(fmt.Sprintf("- status: %s\n", task.Status))
	b.WriteString(fmt.Sprintf("- priority: %d\n", task.Priority))
	if task.Project != nil {
		b.WriteString(fmt.Sprintf("- project: %s (%s)\n", task.Project.Name, task.Project.Slug))
	}
	if task.Assignee != nil {
		name := task.Assignee.DisplayName
		if name == "" {
			name = task.Assignee.ID
		}
		b.WriteString(fmt.Sprintf("- assignee: %s/%s (%s)\n", task.Assignee.Type, task.Assignee.ID, name))
	}
	if desc := strings.TrimSpace(task.Description); desc != "" {
		b.WriteString("- description:\n")
		b.WriteString(trimRunes(desc, 4000))
		b.WriteByte('\n')
	}
	b.WriteString("\nComment thread (oldest first):\n")
	for _, c := range comments {
		marker := ""
		if c.ID == triggerID {
			marker = " ← reply to this"
		}
		b.WriteString(fmt.Sprintf("[%s] %s/%s:%s\n%s\n\n",
			c.CreatedAt.UTC().Format(time.RFC3339),
			c.AuthorType, c.AuthorID, marker,
			trimRunes(c.Body, 2000),
		))
	}
	b.WriteString("Write a helpful board comment reply to the marked mention.\n")
	return b.String()
}

func trimRunes(s string, max int) string {
	r := []rune(s)
	if len(r) <= max {
		return s
	}
	return string(r[:max]) + "…"
}