package worker

import (
	"context"
	"encoding/json"
	"log/slog"
	"strings"
	"sync"
	"time"

	"ai-service/internal/llm"
	"ai-service/internal/model"
	"ai-service/internal/store"
	"ai-service/internal/transcription"
)

const (
	TaskLLMChat        = "llm_chat"
	TaskChatCompletion = "chat_completion"
	TaskCallAnalysis   = "call_analysis"
	TaskTranscription  = "transcription"

	TranscriptionProfile = "whisperx"
)

type Worker struct {
	store         *store.Store
	llm           *llm.Client
	transcriber   *transcription.Client
	workerID      string
	modelProfile  string
	taskTypes     []string
	modelProfiles []string
	pollInterval  time.Duration
	claimLimit    int
	leaseTimeout  time.Duration
}

func New(store *store.Store, llmClient *llm.Client, transcriber *transcription.Client, workerID, modelProfile string, taskTypes, modelProfiles []string, pollInterval, leaseTimeout time.Duration, claimLimit int) *Worker {
	if pollInterval <= 0 {
		pollInterval = 2 * time.Second
	}
	if leaseTimeout <= 0 {
		leaseTimeout = 15 * time.Minute
	}
	if claimLimit <= 0 {
		claimLimit = 4
	}
	if strings.TrimSpace(workerID) == "" {
		workerID = "ai-service-worker"
	}
	if len(modelProfiles) == 0 {
		modelProfiles = []string{modelProfile, TranscriptionProfile}
	}
	return &Worker{
		store:         store,
		llm:           llmClient,
		transcriber:   transcriber,
		workerID:      workerID,
		modelProfile:  modelProfile,
		taskTypes:     taskTypes,
		modelProfiles: modelProfiles,
		pollInterval:  pollInterval,
		claimLimit:    claimLimit,
		leaseTimeout:  leaseTimeout,
	}
}

func (w *Worker) Run(ctx context.Context) {
	ticker := time.NewTicker(w.pollInterval)
	defer ticker.Stop()
	for {
		w.tick(ctx)
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
		}
	}
}

func (w *Worker) tick(ctx context.Context) {
	if reset, err := w.store.RequeueStaleRunning(ctx, w.leaseTimeout, 100); err != nil {
		slog.Error("requeue stale jobs failed", "error", err)
	} else if reset > 0 {
		slog.Warn("requeued stale jobs", "count", reset)
	}
	jobs, err := w.store.ClaimJobs(ctx, model.ClaimJobs{
		WorkerID:      w.workerID,
		TaskTypes:     w.taskTypes,
		ModelProfiles: w.modelProfiles,
		Limit:         w.claimLimit,
	})
	if err != nil {
		slog.Error("claim jobs failed", "error", err)
		return
	}
	if len(jobs) > 1 {
		var wg sync.WaitGroup
		wg.Add(len(jobs))
		for _, job := range jobs {
			go func(job *model.Job) {
				defer wg.Done()
				w.process(ctx, job)
			}(job)
		}
		wg.Wait()
		return
	}
	for _, job := range jobs {
		w.process(ctx, job)
	}
}

func (w *Worker) process(ctx context.Context, job *model.Job) {
	if job.TaskType == TaskTranscription {
		w.processTranscription(ctx, job)
		return
	}
	var input llm.ChatInput
	if err := json.Unmarshal(job.Input, &input); err != nil {
		w.fail(ctx, job, "bad_input", err.Error())
		return
	}
	result, err := w.llm.Chat(ctx, input)
	if err != nil {
		w.fail(ctx, job, classifyLLMError(err), err.Error())
		return
	}
	body, err := json.Marshal(result)
	if err != nil {
		w.fail(ctx, job, "bad_response", err.Error())
		return
	}
	if _, err := w.store.CompleteJob(ctx, job.ID, model.CompleteJob{Result: body}); err != nil {
		slog.Error("complete job failed", "job_id", job.ID, "error", err)
	}
}

func (w *Worker) processTranscription(ctx context.Context, job *model.Job) {
	if w.transcriber == nil {
		w.fail(ctx, job, "provider_unavailable", "whisperx not configured")
		return
	}
	var input transcription.Input
	if err := json.Unmarshal(job.Input, &input); err != nil {
		w.fail(ctx, job, "bad_input", err.Error())
		return
	}
	result, err := w.transcriber.Transcribe(ctx, input)
	if err != nil {
		w.fail(ctx, job, classifyTranscriptionError(err), err.Error())
		return
	}
	body, err := json.Marshal(result)
	if err != nil {
		w.fail(ctx, job, "bad_response", err.Error())
		return
	}
	if _, err := w.store.CompleteJob(ctx, job.ID, model.CompleteJob{Result: body}); err != nil {
		slog.Error("complete transcription job failed", "job_id", job.ID, "error", err)
	}
}

func (w *Worker) fail(ctx context.Context, job *model.Job, code, message string) {
	if _, err := w.store.FailJob(ctx, job.ID, model.FailJob{ErrorCode: code, ErrorMessage: message}); err != nil {
		slog.Error("fail job failed", "job_id", job.ID, "error", err)
	}
}

func classifyTranscriptionError(err error) string {
	if err == nil {
		return "unknown"
	}
	s := strings.ToLower(err.Error())
	switch {
	case strings.Contains(s, "context deadline exceeded") || strings.Contains(s, "timeout"):
		return "timeout"
	case strings.Contains(s, "audio_url is required"):
		return "bad_input"
	case strings.Contains(s, "request has expired") || strings.Contains(s, "accessdenied"):
		return "storage_error"
	case strings.Contains(s, "audio http 4") || strings.Contains(s, "audio is empty"):
		return "bad_audio"
	case strings.Contains(s, "audio download") || strings.Contains(s, "audio http 5"):
		return "storage_error"
	case strings.Contains(s, "whisperx http 4") || strings.Contains(s, "ffmpeg") || strings.Contains(s, "invalid data") || strings.Contains(s, "could not decode"):
		return "bad_audio"
	case strings.Contains(s, "whisperx http 5") || strings.Contains(s, "whisperx do") || strings.Contains(s, "connection refused") || strings.Contains(s, "connection reset") || strings.Contains(s, "closed network connection"):
		return "provider_unavailable"
	case strings.Contains(s, "decode"):
		return "bad_response"
	default:
		return "unknown"
	}
}

func classifyLLMError(err error) string {
	if err == nil {
		return "unknown"
	}
	s := strings.ToLower(err.Error())
	switch {
	case strings.Contains(s, "context deadline exceeded") || strings.Contains(s, "timeout"):
		return "timeout"
	case strings.Contains(s, "connection refused") || strings.Contains(s, "connection reset") || strings.Contains(s, "no route to host") || strings.Contains(s, "llm http 5"):
		return "model_unavailable"
	case strings.Contains(s, "llm http 4") || strings.Contains(s, "messages are required"):
		return "bad_input"
	case strings.Contains(s, "llm decode") || strings.Contains(s, "empty choices"):
		return "bad_response"
	default:
		return "unknown"
	}
}