// Package config loads all runtime configuration from environment variables.
//
// Every knob the transcriber exposes is controlled by an ASR_* environment
// variable so the same binary can be reconfigured without a rebuild.
package config

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"time"
)

// Config holds all runtime configuration derived from environment variables.
type Config struct {
	// ASR_PASSWORD: shared secret required on every API request. If empty,
	// auth is disabled and a loud warning is logged (intended for local use).
	Password string
	// ASR_ADDR: listen address (default ":8080").
	Addr string
	// ASR_DATA_DIR: root for persisted state (default "./data").
	DataDir string
	// ASR_MODEL_DIR: where models live / are auto-downloaded
	// (default "<DataDir>/models").
	ModelDir string
	// ASR_NUM_THREADS: ONNX compute threads (default: min(4, NumCPU)).
	NumThreads int
	// ASR_LANGUAGE: SenseVoice language hint. "auto" detects per segment.
	Language string
	// ASR_USE_ITN: enable inverse text normalization (numbers/punctuation).
	UseITN bool
	// ASR_MAX_RETRIES: automatic retry attempts before a task is marked failed.
	MaxRetries int
	// ASR_MAX_UPLOAD_MB: per-upload size cap (default 512).
	MaxUploadBytes int64
	// ASR_WORKERS: concurrent transcription workers (default 1).
	Workers int
	// ASR_MAX_CONCURRENT: cap on simultaneously in-flight synchronous
	// transcriptions on the OpenAI endpoint. Bounds onnxruntime thread
	// contention under load. Defaults to ASR_NUM_THREADS. Excess requests
	// wait for a slot (or get 503 if the client disconnects while waiting).
	MaxConcurrent int

	// VAD (silero) tuning.
	VadThreshold          float32
	VadMinSpeechDuration  float32
	VadMinSilenceDuration float32
	VadMaxSpeechDuration  float32
	VadWindowSize         int
	VadBufferSeconds      float32

	// ASR_DOWNLOAD_TIMEOUT: timeout for the initial model download.
	DownloadTimeout time.Duration
	// ASR_FFMPEG: path to the ffmpeg binary used to decode formats beep
	// can't (m4a/aac/opus/wma …). Defaults to "ffmpeg" on PATH. Only
	// required when such formats are actually uploaded.
	FFmpegPath string
	// ASR_DECODE_TIMEOUT: per-file decode timeout (beep + ffmpeg fallback).
	DecodeTimeout time.Duration
}

// Load reads the environment and returns a validated Config.
func Load() (Config, error) {
	c := Config{
		Password:              strings.TrimSpace(os.Getenv("ASR_PASSWORD")),
		Addr:                  envStr("ASR_ADDR", ":8080"),
		DataDir:               envStr("ASR_DATA_DIR", "./data"),
		NumThreads:            envInt("ASR_NUM_THREADS", defaultThreads()),
		Language:              envStr("ASR_LANGUAGE", "auto"),
		UseITN:                envBool("ASR_USE_ITN", true),
		MaxRetries:            envInt("ASR_MAX_RETRIES", 3),
		MaxUploadBytes:        int64(envInt("ASR_MAX_UPLOAD_MB", 512)) * 1024 * 1024,
		Workers:               envInt("ASR_WORKERS", 1),
		MaxConcurrent:         envInt("ASR_MAX_CONCURRENT", 0),
		VadThreshold:          float32(envFloat("ASR_VAD_THRESHOLD", 0.5)),
		VadMinSpeechDuration:  float32(envFloat("ASR_VAD_MIN_SPEECH", 0.5)),
		VadMinSilenceDuration: float32(envFloat("ASR_VAD_MIN_SILENCE", 0.5)),
		VadMaxSpeechDuration:  float32(envFloat("ASR_VAD_MAX_SPEECH", 20)),
		VadWindowSize:         envInt("ASR_VAD_WINDOW", 512),
		VadBufferSeconds:      float32(envFloat("ASR_VAD_BUFFER_SECS", 60)),
		DownloadTimeout:       time.Duration(envInt("ASR_DOWNLOAD_TIMEOUT", 1800)) * time.Second,
		FFmpegPath:            envStr("ASR_FFMPEG", "ffmpeg"),
		DecodeTimeout:         time.Duration(envInt("ASR_DECODE_TIMEOUT", 1800)) * time.Second,
	}
	c.ModelDir = envStr("ASR_MODEL_DIR", filepath.Join(c.DataDir, "models"))

	if c.Workers < 1 {
		c.Workers = 1
	}
	if c.MaxConcurrent < 1 {
		c.MaxConcurrent = c.NumThreads
	}
	if c.NumThreads < 1 {
		c.NumThreads = 1
	}
	if c.MaxRetries < 0 {
		c.MaxRetries = 0
	}
	if c.VadMaxSpeechDuration < 1 {
		c.VadMaxSpeechDuration = 1
	}
	if c.DecodeTimeout < time.Minute {
		c.DecodeTimeout = 30 * time.Minute
	}
	if c.VadWindowSize <= 0 {
		c.VadWindowSize = 512
	}
	if c.MaxUploadBytes < 1<<20 {
		c.MaxUploadBytes = 512 << 20
	}
	if c.DownloadTimeout < time.Minute {
		c.DownloadTimeout = 30 * time.Minute
	}

	// Absolutize data dir so relative file paths in persisted state survive
	// regardless of the process working directory at request time.
	if abs, err := filepath.Abs(c.DataDir); err == nil {
		c.DataDir = abs
	}
	if abs, err := filepath.Abs(c.ModelDir); err == nil {
		c.ModelDir = abs
	}
	return c, nil
}

// AuthEnabled reports whether API auth is enforced.
func (c Config) AuthEnabled() bool { return c.Password != "" }

func (c Config) String() string {
	return fmt.Sprintf("addr=%s data=%s models=%s threads=%d lang=%s itn=%t workers=%d maxconcurrent=%d retries=%d vad{thr=%.2f max=%.0fs win=%d}",
		c.Addr, c.DataDir, c.ModelDir, c.NumThreads, c.Language, c.UseITN, c.Workers,
		c.MaxConcurrent, c.MaxRetries, c.VadThreshold, c.VadMaxSpeechDuration, c.VadWindowSize)
}

func defaultThreads() int {
	n := runtime.NumCPU()
	if n > 4 {
		n = 4
	}
	if n < 1 {
		n = 1
	}
	return n
}

func envStr(key, def string) string {
	if v := strings.TrimSpace(os.Getenv(key)); v != "" {
		return v
	}
	return def
}

func envInt(key string, def int) int {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return def
	}
	n, err := strconv.Atoi(v)
	if err != nil {
		return def
	}
	return n
}

func envFloat(key string, def float64) float64 {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return def
	}
	f, err := strconv.ParseFloat(v, 64)
	if err != nil {
		return def
	}
	return f
}

func envBool(key string, def bool) bool {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return def
	}
	b, err := strconv.ParseBool(v)
	if err != nil {
		// Accept "0"/"1" and "yes"/"no" too.
		switch strings.ToLower(v) {
		case "yes", "on", "true", "1":
			return true
		case "no", "off", "false", "0":
			return false
		}
		return def
	}
	return b
}