package stage

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"

	"gitea.maximumdirect.net/eric/narratio/internal/adapters/whisperx"
	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

type transcribeStage struct{}

func (transcribeStage) Name() string { return "transcribe" }

func (transcribeStage) Declares() IODecl {
	return IODecl{
		Inputs: []artifacts.Ref{
			{Kind: "audio", Category: "audio", RelativePath: "audio/*.flac"},
		},
		Outputs: []artifacts.Ref{
			{Kind: "transcript_raw", Category: "transcripts", RelativePath: "transcripts/raw/*.json"},
		},
	}
}

func (transcribeStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*StageResult, error) {
	if env == nil || env.Config == nil {
		return nil, fmt.Errorf("transcribe: stage environment config is required")
	}
	if env.ArtifactStore == nil {
		return nil, fmt.Errorf("transcribe: artifact store is required")
	}
	if env.Config.Pipeline == nil || env.Config.Session == nil {
		return nil, fmt.Errorf("transcribe: resolved config must include pipeline and session")
	}
	if env.WhisperX == nil {
		return nil, fmt.Errorf("transcribe: whisperx adapter is required")
	}

	var sessionID string
	if m != nil {
		sessionID = strings.TrimSpace(m.SessionID)
	}
	if sessionID == "" {
		sessionID = strings.TrimSpace(env.Config.Session.SessionID)
	}
	if sessionID == "" {
		return nil, fmt.Errorf("transcribe: session id is required")
	}

	paths := sessionPathsForEnv(env, sessionID)
	audioFiles, err := discoverPreparedAudio(m, paths.AudioDir)
	if err != nil {
		return nil, fmt.Errorf("transcribe: resolve audio inputs: %w", err)
	}
	if len(audioFiles) == 0 {
		return nil, fmt.Errorf("transcribe: no prepared audio files found")
	}

	concurrency := 1
	if env.Config.Pipeline.WhisperX.Concurrency != nil && *env.Config.Pipeline.WhisperX.Concurrency > 0 {
		concurrency = *env.Config.Pipeline.WhisperX.Concurrency
	}
	if concurrency > len(audioFiles) {
		concurrency = len(audioFiles)
	}

	type job struct {
		speakerID string
		audioPath string
		outPath   string
	}
	jobs := make([]job, 0, len(audioFiles))
	seenSpeaker := map[string]string{}
	for _, audioPath := range audioFiles {
		base := strings.TrimSuffix(filepath.Base(audioPath), filepath.Ext(audioPath))
		if base == "" {
			return nil, fmt.Errorf("transcribe: could not derive speaker id from %q", audioPath)
		}
		if prev, ok := seenSpeaker[base]; ok {
			return nil, fmt.Errorf("transcribe: duplicate speaker/audio basename %q from %q and %q", base, prev, audioPath)
		}
		seenSpeaker[base] = audioPath
		jobs = append(jobs, job{
			speakerID: base,
			audioPath: audioPath,
			outPath:   filepath.Join(paths.TranscriptsRawDir, base+".json"),
		})
	}

	stageCtx, cancel := context.WithCancel(ctx)
	defer cancel()

	var (
		wg        sync.WaitGroup
		jobCh     = make(chan job)
		mu        sync.Mutex
		firstErr  error
		perFile   = map[string]map[string]any{}
		outputRef = map[string]artifacts.Ref{}
	)

	worker := func() {
		defer wg.Done()
		for j := range jobCh {
			if stageCtx.Err() != nil {
				return
			}

			res, runErr := env.WhisperX.Transcribe(stageCtx, whisperx.TranscribeRequest{
				SpeakerID:               j.speakerID,
				AudioPath:               j.audioPath,
				OutputRawTranscriptPath: j.outPath,
			})
			if runErr != nil {
				mu.Lock()
				if firstErr == nil {
					firstErr = fmt.Errorf("speaker %q (%s): %w", j.speakerID, filepath.Base(j.audioPath), runErr)
					cancel()
				}
				mu.Unlock()
				continue
			}

			if strings.TrimSpace(res.OutputRawTranscriptPath) == "" {
				res.OutputRawTranscriptPath = j.outPath
			}
			if filepath.Clean(res.OutputRawTranscriptPath) != filepath.Clean(j.outPath) {
				mu.Lock()
				if firstErr == nil {
					firstErr = fmt.Errorf("speaker %q: adapter output path %q did not match expected %q", j.speakerID, res.OutputRawTranscriptPath, j.outPath)
					cancel()
				}
				mu.Unlock()
				continue
			}
			if err := validateTranscriptJSONFile(j.outPath); err != nil {
				mu.Lock()
				if firstErr == nil {
					firstErr = fmt.Errorf("speaker %q output %q invalid: %w", j.speakerID, j.outPath, err)
					cancel()
				}
				mu.Unlock()
				continue
			}

			meta := map[string]any{
				"attempts":    res.Attempts,
				"http_status": res.HTTPStatus,
				"duration_ms": res.Duration.Milliseconds(),
				"output_path": j.outPath,
			}

			mu.Lock()
			perFile[j.speakerID] = meta
			outputRef[j.speakerID] = artifacts.Ref{
				Kind:         "transcript_raw",
				Category:     "transcripts",
				SessionID:    sessionID,
				AbsolutePath: j.outPath,
			}
			mu.Unlock()
		}
	}

	wg.Add(concurrency)
	for i := 0; i < concurrency; i++ {
		go worker()
	}

dispatch:
	for _, j := range jobs {
		select {
		case <-stageCtx.Done():
			break dispatch
		case jobCh <- j:
		}
	}
	close(jobCh)
	wg.Wait()

	if firstErr != nil {
		return nil, firstErr
	}

	speakers := make([]string, 0, len(perFile))
	for speaker := range perFile {
		speakers = append(speakers, speaker)
	}
	sort.Strings(speakers)

	outputs := make([]artifacts.Ref, 0, len(speakers))
	outputPaths := make([]string, 0, len(speakers))
	orderedPerFile := make(map[string]any, len(speakers))
	for _, speaker := range speakers {
		ref := outputRef[speaker]
		outputs = append(outputs, ref)
		outputPaths = append(outputPaths, ref.AbsolutePath)
		orderedPerFile[speaker] = perFile[speaker]
	}

	retries := 0
	if env.Config.Pipeline.WhisperX.Retries != nil {
		retries = *env.Config.Pipeline.WhisperX.Retries
	}

	return &StageResult{
		Outputs: outputs,
		Metadata: map[string]any{
			"stage":             "transcribe",
			"audio_files_count": len(audioFiles),
			"language":          env.Config.Pipeline.WhisperX.Language,
			"concurrency":       concurrency,
			"retries":           retries,
			"retry_delay":       env.Config.Pipeline.WhisperX.RetryDelay,
			"timeout":           env.Config.Pipeline.WhisperX.Timeout,
			"output_paths":      outputPaths,
			"per_file":          orderedPerFile,
		},
	}, nil
}

func discoverPreparedAudio(m *manifest.Manifest, audioDir string) ([]string, error) {
	fromManifest := make([]string, 0)
	if m != nil {
		for _, in := range m.Inputs {
			if in.Kind != "audio" {
				continue
			}
			p := strings.TrimSpace(in.Path)
			if p == "" {
				continue
			}
			fromManifest = append(fromManifest, filepath.Clean(p))
		}
	}
	if len(fromManifest) > 0 {
		sort.Strings(fromManifest)
		if err := validateAudioFiles(fromManifest); err != nil {
			return nil, err
		}
		return fromManifest, nil
	}

	entries, err := os.ReadDir(audioDir)
	if err != nil {
		return nil, fmt.Errorf("read audio directory %q: %w", audioDir, err)
	}

	out := make([]string, 0)
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		p := filepath.Join(audioDir, entry.Name())
		if !isFlac(p) {
			continue
		}
		out = append(out, p)
	}
	sort.Strings(out)
	if err := validateAudioFiles(out); err != nil {
		return nil, err
	}
	return out, nil
}

func validateAudioFiles(paths []string) error {
	if len(paths) == 0 {
		return nil
	}
	seen := map[string]struct{}{}
	for _, p := range paths {
		clean := filepath.Clean(strings.TrimSpace(p))
		if clean == "" {
			return fmt.Errorf("audio path is required")
		}
		if !isFlac(clean) {
			return fmt.Errorf("audio file %q must have .flac extension", clean)
		}
		info, err := os.Stat(clean)
		if err != nil {
			return fmt.Errorf("audio file %q not found: %w", clean, err)
		}
		if !info.Mode().IsRegular() {
			return fmt.Errorf("audio file %q is not a regular file", clean)
		}
		if _, exists := seen[clean]; exists {
			return fmt.Errorf("duplicate audio file path %q", clean)
		}
		seen[clean] = struct{}{}
	}
	return nil
}

func validateTranscriptJSONFile(path string) error {
	if err := requireFile(path, "raw transcript"); err != nil {
		return err
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("read transcript: %w", err)
	}
	var payload any
	if err := json.Unmarshal(data, &payload); err != nil {
		return fmt.Errorf("decode json: %w", err)
	}
	return nil
}