package service

import (
	"context"
	"log"
	"strings"
	"sync"
	"time"

	"ai-platform/internal/config"
	"ai-platform/internal/model"
)

// Router — LLM-маршрутизатор: классифицирует запрос через ROUTER_MODEL
// и возвращает имя целевой модели.
// Кэширует результат: модель определяется один раз и закрепляется на всю сессию.
type Router struct {
	client *OllamaClient
	cfg    *config.Config

	// Кэш: первое user-сообщение → имя модели
	mu    sync.RWMutex
	cache map[string]string
}

func NewRouter(client *OllamaClient, cfg *config.Config) *Router {
	return &Router{
		client: client,
		cfg:    cfg,
		cache:  make(map[string]string),
	}
}

// Route определяет целевую модель для запроса.
// Модель определяется ОДИН РАЗ через LLM и кэшируется на всю сессию.
func (r *Router) Route(ctx context.Context, modelName string, messages []model.Message) string {
	if modelName != "" && modelName != "auto" {
		return modelName
	}

	// Находим первое "настоящее" user-сообщение
	firstMsg := firstRealUserMessage(messages)
	if firstMsg == "" {
		return r.cfg.GeneralModel
	}

	// Проверяем кэш — если уже классифицировали, возвращаем из кэша
	r.mu.RLock()
	if cached, ok := r.cache[firstMsg]; ok {
		r.mu.RUnlock()
		log.Printf("router: cache hit → %s", cached)
		return cached
	}
	r.mu.RUnlock()

	// Классифицируем через LLM (только один раз за сессию)
	systemPrompt := "You are a router in a multi-model AI system. Your job is to decide which specialist model should handle the user's request. There are three specialist models:\n\n" +
		"1. CODE model — a programming expert. It should handle ANY request where the end goal is producing, modifying, explaining, or debugging software. " +
		"This includes writing code, creating scripts, designing algorithms, working with APIs, databases, DevOps, infrastructure, configuration files, " +
		"or anything else where the output is meant to be executed by a computer. If the user's intent is to build or fix something technical, choose code.\n\n" +
		"2. DOCUMENT model — a text processing expert. It should handle ANY request where the user wants to work WITH existing text or produce written content that is NOT code. " +
		"This includes analyzing, summarizing, translating, rewriting, extracting key points, proofreading, comparing texts, writing essays, reports, articles, letters, " +
		"or any other task where the primary material is natural language text and the output is also natural language text. " +
		"The key distinction: if the user gives you text and wants you to DO something with that text (understand it, transform it, evaluate it), choose document.\n\n" +
		"3. GENERAL model — a conversational assistant. It handles everything that does not fit the other two categories: casual chat, factual questions about the world, " +
		"opinions, recommendations, brainstorming ideas, explanations of non-technical concepts. Choose general ONLY when the request is clearly neither about code nor about text processing.\n\n" +
		"DECISION LOGIC:\n" +
		"- Ask yourself: does the user want SOFTWARE as a result? → code\n" +
		"- Ask yourself: does the user want to PROCESS or PRODUCE written text? → document\n" +
		"- Neither of the above? → general\n" +
		"- When in doubt between code and general → choose code\n" +
		"- When in doubt between document and general → choose document\n" +
		"- general is the LAST resort, not the default\n\n" +
		"Reply with ONLY one word: code, document, or general. Nothing else."

	classifyCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	response, err := r.client.CompleteWithSystem(classifyCtx, r.cfg.RouterModel, systemPrompt, firstMsg)
	if err != nil {
		log.Printf("router: classification failed: %v, falling back to general", err)
		return r.cfg.GeneralModel
	}

	result := r.categoryToModel(response)

	// Сохраняем в кэш — все последующие запросы в этой сессии получат ту же модель
	r.mu.Lock()
	r.cache[firstMsg] = result
	r.mu.Unlock()
	log.Printf("router: cached → %s", result)

	return result
}

// categoryToModel парсит ответ классификатора и возвращает соответствующую модель.
func (r *Router) categoryToModel(response string) string {
	category := strings.ToLower(strings.TrimSpace(response))

	switch {
	case strings.Contains(category, "code") ||
		strings.Contains(category, "код") ||
		strings.Contains(category, "програм"):
		log.Printf("router: classified as CODE → %s (raw: %q)", r.cfg.CodeModel, response)
		return r.cfg.CodeModel
	case strings.Contains(category, "document") ||
		strings.Contains(category, "doc") ||
		strings.Contains(category, "докум") ||
		strings.Contains(category, "текст") ||
		strings.Contains(category, "анализ"):
		log.Printf("router: classified as DOCUMENT → %s (raw: %q)", r.cfg.DocModel, response)
		return r.cfg.DocModel
	default:
		log.Printf("router: classified as GENERAL → %s (raw: %q)", r.cfg.GeneralModel, response)
		return r.cfg.GeneralModel
	}
}

// firstRealUserMessage — последнее user-сообщение перед первым assistant-ответом.
// Пропускает системные инструкции Codex CLI.
func firstRealUserMessage(messages []model.Message) string {
	var lastUser string
	for _, m := range messages {
		if m.Role == "assistant" {
			break
		}
		if m.Role == "user" && !isSystemBoilerplate(m.Content) {
			lastUser = m.Content
		}
	}
	if lastUser == "" {
		for i := len(messages) - 1; i >= 0; i-- {
			if messages[i].Role == "user" && !isSystemBoilerplate(messages[i].Content) {
				return messages[i].Content
			}
		}
	}
	return lastUser
}

// isSystemBoilerplate проверяет, является ли сообщение системными инструкциями Codex CLI
func isSystemBoilerplate(content string) bool {
	if len(content) > 500 {
		return true
	}
	lower := strings.ToLower(content)
	return strings.Contains(lower, "<instructions>") ||
		strings.Contains(lower, "<permissions") ||
		strings.Contains(lower, "<environment_context>") ||
		strings.Contains(lower, "<collaboration_mode>") ||
		strings.Contains(lower, "agents.md")
}