// Package service orchestrates the odidere voice assistant server.
// It coordinates the HTTP server, LLM client, and handles
// graceful shutdown.
package service

import (
	"context"
	"embed"
	"encoding/json"
	"fmt"
	"html/template"
	"io/fs"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"runtime/debug"
	"strings"
	"syscall"
	"time"

	"code.chimeric.al/chimerical/odidere/internal/config"
	"code.chimeric.al/chimerical/odidere/internal/job"
	"code.chimeric.al/chimerical/odidere/internal/llm"
	"code.chimeric.al/chimerical/odidere/internal/service/templates"
	"code.chimeric.al/chimerical/odidere/internal/tool"

	"github.com/google/uuid"
	"github.com/robfig/cron/v3"
	openai "github.com/sashabaranov/go-openai"
)

// Context keys for request-scoped values.
type key string

const (
	logKey key = "log"
	idKey  key = "id"
	ipKey  key = "ip"
)

//go:embed all:static/*
var static embed.FS

// Service is the main application coordinator.
// It owns the HTTP server and all processing clients.
type Service struct {
	cfg    *config.Config
	cron   *cron.Cron
	jobs   []*job.Job
	llm    *llm.Client
	log    *slog.Logger
	mux    *http.ServeMux
	server *http.Server
	tmpl   *template.Template
	tools  *tool.Registry
}

// New creates a Service from the provided configuration.
// It initializes all clients and the HTTP server.
func New(cfg *config.Config, log *slog.Logger) (*Service, error) {
	var svc = &Service{
		cfg: cfg,
		log: log,
		mux: http.NewServeMux(),
	}

	// Setup tool registry.
	registry, err := tool.NewRegistry(cfg.Tools)
	if err != nil {
		return nil, fmt.Errorf("load tools: %v", err)
	}
	svc.tools = registry

	// Create LLM client.
	llmClient, err := llm.NewClient(cfg.LLM, registry, log)
	if err != nil {
		return nil, fmt.Errorf("create LLM client: %v", err)
	}
	svc.llm = llmClient

	// Convert job configs to jobs.
	jobs := make([]*job.Job, 0, len(cfg.Jobs))
	for _, jc := range cfg.Jobs {
		j, err := job.New(jc, log, svc.llm)
		if err != nil {
			return nil, fmt.Errorf("create job %q: %w", jc.Name, err)
		}
		jobs = append(jobs, j)
	}
	svc.jobs = jobs

	// Parse templates.
	tmpl, err := templates.Parse()
	if err != nil {
		return nil, fmt.Errorf("parse templates: %v", err)
	}
	svc.tmpl = tmpl

	// Setup static file server.
	staticFS, err := fs.Sub(static, "static")
	if err != nil {
		return nil, fmt.Errorf("setup static fs: %v", err)
	}

	// Register routes.
	svc.mux.HandleFunc("GET /", svc.home)
	svc.mux.HandleFunc("GET /status", svc.status)
	svc.mux.Handle(
		"GET /static/",
		http.StripPrefix(
			"/static/", http.FileServer(http.FS(staticFS)),
		),
	)
	svc.mux.HandleFunc("POST /v1/chat/voice", svc.chat)
	svc.mux.HandleFunc("POST /v1/chat/voice/stream", svc.chatStream)
	svc.mux.HandleFunc("GET /v1/models", svc.models)

	svc.server = &http.Server{
		Addr:    cfg.Address,
		Handler: svc,
	}

	return svc, nil
}

// ServeHTTP implements http.Handler. It logs requests, assigns a UUID,
// sets context values, handles panics, and delegates to the mux.
func (svc *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	var (
		start = time.Now()
		id    = uuid.NewString()
		ip    = func() string {
			if ip := r.Header.Get("X-Forwarded-For"); ip != "" {
				if idx := strings.Index(ip, ","); idx != -1 {
					return strings.TrimSpace(ip[:idx])
				}
				return ip
			}
			return r.RemoteAddr
		}()
		log = svc.log.With(slog.Group(
			"request",
			slog.String("id", id),
			slog.String("ip", ip),
			slog.String("method", r.Method),
			slog.String("path", r.URL.Path),
		))
	)

	// Log completion time.
	defer func() {
		log.InfoContext(
			r.Context(),
			"completed",
			slog.Duration("duration", time.Since(start)),
		)
	}()

	// Panic recovery.
	defer func() {
		if err := recover(); err != nil {
			log.ErrorContext(
				r.Context(),
				"panic recovered",
				slog.Any("error", err),
				slog.String("stack", string(debug.Stack())),
			)
			http.Error(
				w,
				http.StatusText(
					http.StatusInternalServerError,
				),
				http.StatusInternalServerError,
			)
		}
	}()

	// Enrich context with request-scoped values.
	ctx := r.Context()
	ctx = context.WithValue(ctx, logKey, log)
	ctx = context.WithValue(ctx, idKey, id)
	ctx = context.WithValue(ctx, ipKey, ip)
	r = r.WithContext(ctx)

	log.InfoContext(ctx, "handling")

	// Pass the request on to the multiplexer.
	svc.mux.ServeHTTP(w, r)
}

// Run starts the service and blocks until shutdown.
// Shutdown is triggered by SIGINT or SIGTERM.
func (svc *Service) Run(ctx context.Context) error {
	svc.log.Info(
		"starting odidere",
		slog.Group(
			"llm",
			slog.String("url", svc.cfg.LLM.URL),
			slog.String("model", svc.cfg.LLM.Model),
		),
		slog.Group(
			"server",
			slog.String("address", svc.cfg.Address),
		),
		slog.Group(
			"tools",
			slog.Int("count", len(svc.tools.List())),
			slog.Any(
				"names",
				strings.Join(svc.tools.List(), ","),
			),
		),
		slog.Group(
			"tts_url",
			slog.String("url", svc.cfg.TTS.URL),
			slog.String("default_voice", svc.cfg.TTS.Voice),
		),
		slog.Group(
			"stt_url",
			slog.String("url", svc.cfg.STT.URL),
		),
		slog.Group(
			"jobs",
			slog.Int("count", svc.JobCount()),
		),
		slog.Any("shutdown_timeout", svc.cfg.GetShutdownTimeout()),
	)

	// Setup signal handling for graceful shutdown.
	ctx, cancel := signal.NotifyContext(
		ctx,
		os.Interrupt, syscall.SIGTERM,
	)
	defer cancel()

	// Register jobs with cron scheduler.
	svc.cron = cron.New()
	for _, j := range svc.jobs {
		if !j.IsEnabled() {
			svc.log.Info("job disabled", slog.String("name", j.Name()))
			continue
		}
		entry, err := svc.cron.AddFunc(j.Schedule(), func() {
			result := j.Run(ctx)
			if result.Error != nil {
				svc.log.Error("job failed",
					slog.String("name", j.Name()),
					slog.Any("error", result.Error),
					slog.Duration(
						"duration", result.Duration,
					),
				)
			} else {
				svc.log.Info("job completed",
					slog.String("name", j.Name()),
					slog.Duration(
						"duration", result.Duration,
					),
				)
			}
		})
		if err != nil {
			svc.log.Error("failed to schedule job",
				slog.String("name", j.Name()),
				slog.Any("error", err),
			)
			continue
		}
		svc.log.Info("job scheduled",
			slog.String("name", j.Name()),
			slog.String("schedule", j.Schedule()),
			slog.Int("entry_id", int(entry)),
		)
	}
	svc.cron.Start()

	// Start HTTP server in background.
	var errs = make(chan error, 1)
	go func() {
		svc.log.Info(
			"HTTP server listening",
			slog.String("address", svc.cfg.Address),
		)
		if err := svc.server.ListenAndServe(); err != nil &&
			err != http.ErrServerClosed {
			errs <- err
		}
		close(errs)
	}()

	// Wait for shutdown signal or server error.
	select {
	case <-ctx.Done():
		svc.log.Info("shutdown signal received")
	case err := <-errs:
		if err != nil {
			return fmt.Errorf("server error: %w", err)
		}
	}

	// Graceful shutdown with timeout.
	shutdownCtx, shutdownCancel := context.WithTimeout(
		context.Background(),
		svc.cfg.GetShutdownTimeout(),
	)
	defer shutdownCancel()

	// Stop cron scheduler — in-flight jobs continue to completion.
	svc.log.Info("stopping job scheduler")
	svc.cron.Stop()

	svc.log.Info("shutting down HTTP server")
	if err := svc.server.Shutdown(shutdownCtx); err != nil {
		svc.log.Warn(
			"shutdown timeout reached",
			slog.Any("error", err),
		)
	}

	svc.log.Info("terminating")
	return nil
}

// ListJobs returns all registered jobs.
func (svc *Service) ListJobs() []*job.Job {
	return svc.jobs
}

// JobCount returns the number of registered jobs.
func (svc *Service) JobCount() int {
	return len(svc.jobs)
}

func (svc *Service) home(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := svc.tmpl.ExecuteTemplate(
		w, "index.gohtml", struct {
			TTSURL          string
			TTSDefaultVoice string
			STTURL          string
		}{
			TTSURL:          svc.cfg.TTS.URL,
			TTSDefaultVoice: svc.cfg.TTS.Voice,
			STTURL:          svc.cfg.STT.URL,
		},
	); err != nil {
		log.ErrorContext(
			ctx, "template error", slog.Any("error", err),
		)
		http.Error(
			w,
			http.StatusText(http.StatusInternalServerError),
			http.StatusInternalServerError,
		)
	}
}

// status returns server status.
func (svc *Service) status(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
}

// Request is the incoming request format for the chat endpoints.
type Request struct {
	// Messages is the conversation history.
	Messages []openai.ChatCompletionMessage `json:"messages"`
	// Model is the LLM model ID. If empty, the default model is used.
	Model string `json:"model,omitempty"`
	// SystemMessage overrides the configured system message for this request.
	SystemMessage string `json:"system_message,omitempty"`
	// Voice is the voice ID for TTS.
	Voice string `json:"voice,omitempty"`
}

// Response is the response format for chat and voice endpoints.
type Response struct {
	// Messages is the full list of messages generated during the query,
	// including tool calls and tool results.
	Messages []openai.ChatCompletionMessage `json:"messages,omitempty"`
	// Model is the LLM model used for the response.
	Model string `json:"used_model,omitempty"`
	// Voice is the voice used for TTS synthesis.
	Voice string `json:"used_voice,omitempty"`
}

// chat processes text chat requests.
func (svc *Service) chat(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	// Parse request.
	r.Body = http.MaxBytesReader(w, r.Body, 32<<20)
	var req Request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		log.ErrorContext(
			ctx,
			"failed to decode request",
			slog.Any("error", err),
		)
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	// Validate messages.
	if len(req.Messages) == 0 {
		http.Error(w, "messages required", http.StatusBadRequest)
		return
	}
	log.InfoContext(ctx, "messages",
		slog.Any("data", req.Messages),
	)

	// Get LLM response.
	var model = req.Model
	if model == "" {
		model = svc.llm.DefaultModel()
	}
	msgs, err := svc.llm.Query(ctx, req.Messages, model, req.SystemMessage, 0)
	if err != nil {
		log.ErrorContext(
			ctx,
			"LLM request failed",
			slog.Any("error", err),
		)
		http.Error(w, "LLM error", http.StatusInternalServerError)
		return
	}
	if len(msgs) == 0 {
		http.Error(
			w,
			"no response from LLM",
			http.StatusInternalServerError,
		)
		return
	}
	final := msgs[len(msgs)-1]
	log.InfoContext(
		ctx,
		"LLM response",
		slog.String("text", final.Content),
		slog.String("model", model),
	)

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(Response{
		Messages: msgs,
		Model:    model,
		Voice:    req.Voice,
	}); err != nil {
		log.ErrorContext(
			ctx,
			"failed to json encode response",
			slog.Any("error", err),
		)
	}
}

// StreamMessage is the SSE event payload for the streaming chat endpoint.
type StreamMessage struct {
	// Error is an error message, if any.
	Error string `json:"error,omitempty"`
	// Message is the chat completion message.
	Message openai.ChatCompletionMessage `json:"message"`
	// Model is the LLM model used for the response.
	Model string `json:"model,omitempty"`
	// Voice is the voice used for TTS synthesis.
	Voice string `json:"voice,omitempty"`
}

// chatStream processes chat requests with streaming SSE output.
func (svc *Service) chatStream(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	// Check that the response writer supports flushing.
	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(
			w,
			"streaming not supported",
			http.StatusInternalServerError,
		)
		return
	}

	// Parse request.
	r.Body = http.MaxBytesReader(w, r.Body, 32<<20)
	var req Request
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		log.ErrorContext(
			ctx,
			"failed to decode request",
			slog.Any("error", err),
		)
		http.Error(w, "invalid request", http.StatusBadRequest)
		return
	}

	// Validate messages.
	if len(req.Messages) == 0 {
		http.Error(w, "messages required", http.StatusBadRequest)
		return
	}

	// Set SSE headers.
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Content-Type", "text/event-stream")

	// Helper to send an SSE event.
	send := func(msg StreamMessage) {
		data, err := json.Marshal(msg)
		if err != nil {
			log.ErrorContext(ctx, "failed to marshal SSE event",
				slog.Any("error", err),
			)
			return
		}
		fmt.Fprintf(w, "event: message\ndata: %s\n\n", data)
		flusher.Flush()
	}

	// Get model.
	var model = req.Model
	if model == "" {
		model = svc.llm.DefaultModel()
	}

	// Start streaming LLM query.
	var (
		events = make(chan llm.StreamEvent)
		llmErr error
	)
	go func() {
		llmErr = svc.llm.QueryStream(ctx, req.Messages, model, req.SystemMessage, 0, events)
	}()

	// Consume events and send as SSE.
	var last StreamMessage
	for evt := range events {
		msg := StreamMessage{Message: evt.Message}

		// Track the last assistant message for TTS.
		if evt.Message.Role == openai.ChatMessageRoleAssistant &&
			len(evt.Message.ToolCalls) == 0 {
			last = msg
			continue
		}

		send(msg)
	}
	// Check for LLM errors.
	if llmErr != nil {
		log.ErrorContext(
			ctx,
			"LLM stream failed",
			slog.Any("error", llmErr),
		)
		send(StreamMessage{
			Message: openai.ChatCompletionMessage{
				Role: openai.ChatMessageRoleAssistant,
			},
			Error: fmt.Sprintf("LLM error: %v", llmErr),
		})
		return
	}

	last.Model = model
	last.Voice = req.Voice
	send(last)
}

// models returns available LLM models.
func (svc *Service) models(w http.ResponseWriter, r *http.Request) {
	var (
		ctx = r.Context()
		log = ctx.Value(logKey).(*slog.Logger)
	)

	models, err := svc.llm.ListModels(ctx)
	if err != nil {
		log.ErrorContext(
			ctx,
			"failed to list models",
			slog.Any("error", err),
		)
		http.Error(
			w,
			"failed to list models",
			http.StatusInternalServerError,
		)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(struct {
		Models       []openai.Model `json:"models"`
		DefaultModel string         `json:"default_model"`
	}{
		Models:       models,
		DefaultModel: svc.llm.DefaultModel(),
	}); err != nil {
		log.ErrorContext(
			ctx,
			"failed to encode models response",
			slog.Any("error", err),
		)
	}
}