package config

import (
	"os"
	"strings"
	"time"
)

// Config holds all runtime configuration, loaded from environment variables.
// See .env.example for the full list and defaults.
type Config struct {
	Port         string
	BaseURL      string
	DatabasePath string
	ImageDir     string // on-disk store for editor image uploads
	// DictPath is DreamDict's built dict.db, read-only, sitting beside
	// petal.db. It is what gives Petal French, European Portuguese and Spanish
	// word lookups; without it only the embedded English/Chinese datasets
	// exist, which is exactly how a laptop checkout runs. A missing file is
	// therefore not an error — see lexicon.OpenDreamDict.
	DictPath string

	// LLM
	LLMBackend   string // "vllm" | "ollama"
	LLMEndpoint  string
	LLMModel     string // checkpoint model (small, fast)
	LLMChatModel string // Ask Petal model; falls back to LLMModel if empty
	LLMTimeout   time.Duration

	// TTS (read-aloud). Off unless TTSEndpoint is set — when empty, the /api/tts
	// route isn't mounted and the frontend falls back to the browser's Web Speech
	// API. Endpoint points at a local Piper HTTP server.
	TTSEndpoint string // Piper instance serving the English voice; also the on/off switch
	// TTSVoices is every language Petal can read aloud, keyed by base language
	// tag ("en", "zh", "pt", …). Each Piper server loads exactly one model, so
	// a language *is* an instance — and the instances are discovered from the
	// environment rather than named in this struct: one
	// TTS_ENDPOINT_<LANG>/TTS_VOICE_<LANG> pair per language, so the fr and es
	// pairs cost a compose service and two lines of .env rather than a code
	// change. English keeps the unsuffixed TTS_ENDPOINT/TTS_VOICE_EN it has
	// always had.
	TTSVoices map[string]TTSVoice
	// TTSPath is the path Piper serves synthesis on. Piper moved it from "/" to
	// "/synthesize" in 1.6.0 with an unchanged request body, so this is a
	// version knob, not a feature: millenia's older server keeps the default,
	// the containerised sidecars set "/synthesize".
	TTSPath     string
	TTSCacheDir string // on-disk store for synthesized clips (content-addressed)
	TTSTimeout  time.Duration
	TTSFormat   string // mp3 | opus | wav — mp3/opus transcode Piper's WAV via ffmpeg

	// Auth. OIDC against Authentik. Login is enabled only when the issuer, the
	// client id and the secret are all present; with any of them missing Petal
	// falls back to the single hardcoded local user, which is what local
	// development wants and what every deployment did before Phase 16.
	AuthentikURL          string // issuer URL of the Petal provider in Authentik
	AuthentikClientID     string
	AuthentikClientSecret string
	// AllowedSubs gates who may sign in, as a comma-separated list of OIDC
	// subject ids and/or email addresses. Empty means everyone Authentik
	// authenticates — right for a single-household instance, wrong the moment
	// the IdP serves an audience wider than Petal's.
	AllowedSubs string
}

// TTSVoice is one Piper instance and the single voice it has loaded.
type TTSVoice struct {
	Endpoint string
	Voice    string
}

// AuthEnabled reports whether real logins are configured. When false, Petal
// resolves every request to the local user.
func (c *Config) AuthEnabled() bool {
	return c.AuthentikURL != "" && c.AuthentikClientID != "" && c.AuthentikClientSecret != ""
}

// Load reads configuration from the environment, applying sane local-dev defaults.
func Load() *Config {
	return &Config{
		Port:         env("PORT", "8080"),
		BaseURL:      env("BASE_URL", "http://localhost:8080"),
		DatabasePath: env("DATABASE_PATH", "./data/petal.db"),
		ImageDir:     env("IMAGE_DIR", "./data/images"),
		DictPath:     env("DICT_PATH", "./data/dict.db"),

		LLMBackend:   env("LLM_BACKEND", "vllm"),
		LLMEndpoint:  env("LLM_ENDPOINT", "http://localhost:8000"),
		LLMModel:     env("LLM_MODEL", ""),
		LLMChatModel: env("LLM_CHAT_MODEL", ""),
		LLMTimeout:   envDuration("LLM_TIMEOUT", 30*time.Second),

		TTSEndpoint: env("TTS_ENDPOINT", ""),
		TTSVoices:   ttsVoices(os.Environ()),
		TTSPath:     env("TTS_PATH", "/"),
		TTSCacheDir: env("TTS_CACHE_DIR", "./data/tts"),
		TTSTimeout:  envDuration("TTS_TIMEOUT", 15*time.Second),
		TTSFormat:   env("TTS_AUDIO_FORMAT", "mp3"),

		AuthentikURL:          env("AUTHENTIK_URL", ""),
		AuthentikClientID:     env("AUTHENTIK_CLIENT_ID", ""),
		AuthentikClientSecret: env("AUTHENTIK_CLIENT_SECRET", ""),
		AllowedSubs:           env("PETAL_ALLOWED_SUBS", ""),
	}
}

// ttsVoices reads the Piper instances out of an environment slice (as returned
// by os.Environ) into a map keyed by base language tag.
//
// English is the unsuffixed pair, TTS_ENDPOINT + TTS_VOICE_EN, because that is
// what every deployment already sets and read-aloud has always been English
// first. Every other language is a TTS_ENDPOINT_<LANG>/TTS_VOICE_<LANG> pair,
// discovered rather than enumerated — TTS_ENDPOINT_ZH is what millenia and the
// VPS already use, and TTS_ENDPOINT_PT is all the Portuguese pair needs.
//
// <LANG> is the *base* tag: an environment variable name cannot hold the hyphen
// in "pt-PT", and the handler routes on the base tag anyway (a request for
// pt-PT, pt-BR or bare pt reaches the same instance, because there is only one
// Portuguese voice loaded). A pair is ignored unless both halves are set: half
// a configuration should read as "no voice for this language" and fall back to
// the browser, not as an instance that answers every request with an error.
func ttsVoices(environ []string) map[string]TTSVoice {
	vals := make(map[string]string, len(environ))
	for _, kv := range environ {
		if k, v, ok := strings.Cut(kv, "="); ok {
			vals[k] = v
		}
	}

	voices := map[string]TTSVoice{}
	add := func(lang, endpoint, voice string) {
		endpoint = strings.TrimRight(strings.TrimSpace(endpoint), "/")
		voice = strings.TrimSpace(voice)
		if endpoint == "" || voice == "" {
			return
		}
		voices[lang] = TTSVoice{Endpoint: endpoint, Voice: voice}
	}

	// The two languages that shipped before this was a map keep their voice
	// defaults, so an existing deployment that names only the endpoints (as
	// millenia's unit does) sounds exactly as it did.
	voiceOr := func(key, fallback string) string {
		if v := strings.TrimSpace(vals[key]); v != "" {
			return v
		}
		return fallback
	}

	add("en", vals["TTS_ENDPOINT"], voiceOr("TTS_VOICE_EN", "en_US-amy-medium"))
	for k, endpoint := range vals {
		suffix, ok := strings.CutPrefix(k, "TTS_ENDPOINT_")
		if !ok || suffix == "" {
			continue
		}
		voice := vals["TTS_VOICE_"+suffix]
		if suffix == "ZH" {
			voice = voiceOr("TTS_VOICE_ZH", "zh_CN-huayan-medium")
		}
		add(strings.ToLower(suffix), endpoint, voice)
	}
	return voices
}

func env(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func envDuration(key string, fallback time.Duration) time.Duration {
	if v := os.Getenv(key); v != "" {
		if d, err := time.ParseDuration(v); err == nil {
			return d
		}
	}
	return fallback
}