package api

import (
    "fmt"
    "io"
    "os"
    "path/filepath"
    "strings"
    "sync"
)

// Subdirectories under models_dir that hold non-Whisper assets (VAD, punctuation, etc.).
var reservedModelSubdirs = map[string]struct{}{
    "vad":         {},
    "punctuation": {},
}

// Top-level .bin files that are not Whisper STT models.
var excludedWhisperModelFiles = map[string]struct{}{
    "vad.bin": {},
}

type Registry struct {
    dir string
    mu  sync.RWMutex
}

func NewRegistry(dir string) *Registry {
    return &Registry{dir: dir}
}

func isReservedModelSubdir(name string) bool {
    _, ok := reservedModelSubdirs[strings.ToLower(name)]
    return ok
}

func isWhisperModelFile(name string) bool {
    if !strings.HasSuffix(strings.ToLower(name), ".bin") {
        return false
    }
    _, excluded := excludedWhisperModelFiles[strings.ToLower(name)]
    return !excluded
}

func (r *Registry) List() ([]string, error) {
    r.mu.RLock()
    defer r.mu.RUnlock()
    entries, err := os.ReadDir(r.dir)
    if err != nil {
        if os.IsNotExist(err) {
            return nil, nil
        }
        return nil, err
    }
    var models []string
    for _, e := range entries {
        if e.IsDir() {
            continue
        }
        name := e.Name()
        if !isWhisperModelFile(name) {
            continue
        }
        models = append(models, strings.TrimSuffix(name, filepath.Ext(name)))
    }
    return models, nil
}

func (r *Registry) Path(id string) (string, error) {
    if id == "" {
        return "", fmt.Errorf("model id is required")
    }
    if strings.Contains(id, "/") || strings.Contains(id, "..") {
        return "", fmt.Errorf("invalid model id")
    }
    if isReservedModelSubdir(id) {
        return "", fmt.Errorf("model %q not found", id)
    }
    r.mu.RLock()
    defer r.mu.RUnlock()
    candidates := []string{
        filepath.Join(r.dir, id+".bin"),
        filepath.Join(r.dir, id),
        filepath.Join(r.dir, "ggml-"+id+".bin"),
    }
    for _, p := range candidates {
        if st, err := os.Stat(p); err == nil && !st.IsDir() && isWhisperModelFile(filepath.Base(p)) {
            return p, nil
        }
    }
    return "", fmt.Errorf("model %q not found", id)
}

func (r *Registry) Delete(id string) error {
    p, err := r.Path(id)
    if err != nil {
        return err
    }
    r.mu.Lock()
    defer r.mu.Unlock()
    return os.Remove(p)
}

func (r *Registry) Import(id string, src io.Reader) error {
    if id == "" {
        return fmt.Errorf("model id is required")
    }
    if strings.Contains(id, "/") || strings.Contains(id, "..") {
        return fmt.Errorf("invalid model id")
    }
    if isReservedModelSubdir(id) {
        return fmt.Errorf("invalid model id")
    }
    r.mu.Lock()
    defer r.mu.Unlock()
    if err := os.MkdirAll(r.dir, 0o755); err != nil {
        return err
    }
    dst := filepath.Join(r.dir, id+".bin")
    f, err := os.Create(dst)
    if err != nil {
        return err
    }
    defer f.Close()

    if _, err := io.Copy(f, src); err != nil {
        os.Remove(dst)
        return err
    }
    return nil
}

func (r *Registry) Open(id string) (*os.File, error) {
    p, err := r.Path(id)
    if err != nil {
        return nil, err
    }
    return os.Open(p)
}

// Resolve maps an OpenAI-style model name to a local whisper model id.
func (r *Registry) Resolve(id, defaultModel string) (string, error) {
    id = strings.TrimSpace(id)
    if id == "" {
        id = strings.TrimSpace(defaultModel)
    }
    if id == "" {
        models, err := r.List()
        if err != nil {
            return "", err
        }
        if len(models) == 0 {
            return "", fmt.Errorf("model is required")
        }
        return models[0], nil
    }
    if id == "whisper-1" {
        if dm := strings.TrimSpace(defaultModel); dm != "" {
            if _, err := r.Path(dm); err == nil {
                return dm, nil
            }
        }
        models, err := r.List()
        if err != nil {
            return "", err
        }
        if len(models) == 0 {
            return "", fmt.Errorf("no whisper models installed")
        }
        return models[0], nil
    }
    if _, err := r.Path(id); err == nil {
        return id, nil
    }
    if alt := strings.TrimPrefix(id, "whisper-"); alt != id {
        if _, err := r.Path(alt); err == nil {
            return alt, nil
        }
    }
    return "", fmt.Errorf("model %q not found", id)
}