package app

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"slices"
	"strconv"
	"strings"

	"gitea.nik4nao.com/nik/home-services/ai-gateway/internal/core/domain"
	"gitea.nik4nao.com/nik/home-services/ai-gateway/internal/core/ports/driven"
)

// QueryResult is the app-layer response mapped onto the gRPC API.
type QueryResult struct {
	Reply       string
	Intent      string
	ActionTaken bool
}

// QueryApp orchestrates one AI query request.
type QueryApp struct {
	llm   driven.LLMClient
	ha    driven.HAClient
	cache *domain.LightCache
	log   *slog.Logger
}

// NewQueryApp constructs the AI query application service.
func NewQueryApp(llm driven.LLMClient, ha driven.HAClient, cache *domain.LightCache, log *slog.Logger) *QueryApp {
	return &QueryApp{llm: llm, ha: ha, cache: cache, log: log}
}

// Query runs the full intent parsing and dispatch flow for one user request.
func (a *QueryApp) Query(ctx context.Context, text string) (QueryResult, error) {
	lights, err := a.cache.Get(ctx)
	if err != nil {
		a.log.Error("light cache refresh failed", "err", err)
		return QueryResult{
			Reply:       "I couldn't reach Home Assistant right now.",
			ActionTaken: false,
		}, nil
	}

	prompt := domain.BuildPrompt(text, promptLightLines(lights))
	raw, err := a.llm.Generate(ctx, prompt)
	if err != nil {
		return QueryResult{}, err
	}

	var intent domain.Intent
	if err := json.Unmarshal([]byte(raw), &intent); err != nil {
		a.log.Warn("llm returned invalid json", "text", text, "raw_output", raw)
		return QueryResult{
			Reply:       "I didn't understand that.",
			Intent:      domain.IntentNone,
			ActionTaken: false,
		}, nil
	}

	switch intent.Name {
	case domain.IntentTurnOnLight:
		entityID, ok := resolveLightEntity(intent.Entity, lights)
		if !ok {
			return QueryResult{Reply: "I couldn't find that light.", Intent: intent.Name}, nil
		}
		params, err := ParseLightParams(intent.Params)
		if err != nil {
			return QueryResult{
				Reply:       "I couldn't understand the light settings.",
				Intent:      intent.Name,
				ActionTaken: false,
			}, nil
		}
		if err := a.ha.TurnOnLight(ctx, entityID, params); err != nil {
			a.log.Error("turn on light failed", "entity_id", entityID, "err", err)
			return QueryResult{
				Reply:       "I couldn't reach Home Assistant right now.",
				Intent:      intent.Name,
				ActionTaken: false,
			}, nil
		}
		return QueryResult{
			Reply:       fallbackReply(intent.Reply, fmt.Sprintf("Turned on `%s`.", displayLightName(entityID, lights))),
			Intent:      intent.Name,
			ActionTaken: true,
		}, nil
	case domain.IntentTurnOffLight:
		entityID, ok := resolveLightEntity(intent.Entity, lights)
		if !ok {
			return QueryResult{Reply: "I couldn't find that light.", Intent: intent.Name}, nil
		}
		if err := a.ha.TurnOffLight(ctx, entityID); err != nil {
			a.log.Error("turn off light failed", "entity_id", entityID, "err", err)
			return QueryResult{
				Reply:       "I couldn't reach Home Assistant right now.",
				Intent:      intent.Name,
				ActionTaken: false,
			}, nil
		}
		return QueryResult{
			Reply:       fallbackReply(intent.Reply, fmt.Sprintf("Turned off `%s`.", displayLightName(entityID, lights))),
			Intent:      intent.Name,
			ActionTaken: true,
		}, nil
	case domain.IntentListLights:
		return QueryResult{
			Reply:       formatLightListReply(lights),
			Intent:      intent.Name,
			ActionTaken: false,
		}, nil
	case domain.IntentNone:
		fallthrough
	default:
		return QueryResult{
			Reply:       fallbackReply(intent.Reply, "I didn't understand that."),
			Intent:      intent.Name,
			ActionTaken: false,
		}, nil
	}
}

func promptLightLines(lights []driven.Light) []string {
	lines := make([]string, 0, len(lights))
	for _, light := range lights {
		label := light.FriendlyName
		if label == "" {
			label = light.EntityID
		}
		lines = append(lines, fmt.Sprintf("- %s (%s) state=%s", label, light.EntityID, light.State))
	}
	return lines
}

func resolveLightEntity(value string, lights []driven.Light) (string, bool) {
	needle := strings.TrimSpace(strings.ToLower(value))
	if needle == "" {
		return "", false
	}
	idx := slices.IndexFunc(lights, func(light driven.Light) bool {
		return strings.ToLower(light.EntityID) == needle || strings.ToLower(light.FriendlyName) == needle
	})
	if idx != -1 {
		return lights[idx].EntityID, true
	}
	idx = slices.IndexFunc(lights, func(light driven.Light) bool {
		return strings.Contains(strings.ToLower(light.FriendlyName), needle)
	})
	if idx != -1 {
		return lights[idx].EntityID, true
	}
	return "", false
}

func displayLightName(entityID string, lights []driven.Light) string {
	idx := slices.IndexFunc(lights, func(light driven.Light) bool { return light.EntityID == entityID })
	if idx == -1 || lights[idx].FriendlyName == "" {
		return entityID
	}
	return lights[idx].FriendlyName
}

func fallbackReply(reply, fallback string) string {
	if strings.TrimSpace(reply) == "" {
		return fallback
	}
	return reply
}

func formatLightListReply(lights []driven.Light) string {
	if len(lights) == 0 {
		return "No lights found."
	}
	lines := make([]string, 0, len(lights)+1)
	lines = append(lines, "Known lights:")
	for _, light := range lights {
		label := light.FriendlyName
		if label == "" {
			label = light.EntityID
		}
		lines = append(lines, fmt.Sprintf("- %s (%s) [%s]", label, light.EntityID, light.State))
	}
	return strings.Join(lines, "\n")
}

// ParseLightParams converts string params into the protobuf-compatible values the HA adapter expects.
func ParseLightParams(params map[string]string) (map[string]string, error) {
	if len(params) == 0 {
		return map[string]string{}, nil
	}
	normalized := make(map[string]string, len(params))
	for key, value := range params {
		switch key {
		case "brightness", "brightness_pct", "color_temp", "color_temp_kelvin":
			if _, err := strconv.ParseUint(value, 10, 32); err != nil {
				return nil, fmt.Errorf("invalid %s value %q: %w", key, value, err)
			}
		}
		normalized[key] = value
	}
	return normalized, nil
}