package config

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/BurntSushi/toml"

	"code.m3ta.dev/m3tam3re/talk/internal/queue"
)

// Allowed values for audio.sink (public contract).
const (
	SinkOto  = "oto"
	SinkNull = "null"
)

// DefaultServerPort is the daemon's default HTTP port on 127.0.0.1.
const DefaultServerPort = 7800

// DefaultRateLimit is the anti-spam law's default: one announcement per
// 30 seconds. "0s" disables the limit.
const DefaultRateLimit = 30 * time.Second

// DefaultMaxText is the default cap on announcement length in characters:
// two to three sentences, roughly 25 seconds of speech. 0 = unlimited.
const DefaultMaxText = 400

// DefaultMaxAge is the default longest wait in the queue; whatever parks
// longer is stale and gets discarded. "0s" = unlimited.
const DefaultMaxAge = 2 * time.Minute

// DefaultLang is the language assumed when detection cannot decide (empty,
// numbers, ties). Also the language of talk's own announcements such as the
// wrap result when the label gives no hint.
const DefaultLang = "en"

// Config is the effective configuration after all layers were applied.
type Config struct {
	Audio Audio `toml:"audio"`

	// Server configures the daemon's HTTP server on 127.0.0.1.
	Server Server `toml:"server"`

	// Queue holds the daemon's anti-spam laws.
	Queue Queue `toml:"queue"`

	// Daemon configures the background process (autostart).
	Daemon Daemon `toml:"daemon"`

	// Lang is the fallback language (de | en) when detection cannot decide,
	// and the language of talk's own announcements. Default "en"; env
	// TALK_LANG.
	Lang string `toml:"lang"`

	// Provider pins the chain to exactly one provider (for example
	// `provider = "elevenlabs"`); empty = the full default chain
	// (elevenlabs → openai → edge → osbuiltin). The --provider flag beats
	// this value. Valid names are checked by the provider layer.
	Provider string `toml:"provider"`

	// Providers holds per-provider settings (endpoint, model):
	// `[providers.elevenlabs] endpoint = "…"`. The key is plural so the pin
	// (`provider`) and the settings table can coexist in TOML.
	Providers map[string]ProviderSettings `toml:"providers"`

	// Voice is the voice mapping `voice.<provider>.<lang> = id`, for example
	// `[voice.elevenlabs] de = "21m00Tcm4TlvDq8ikWAM"`. It beats the built-in
	// neutral defaults; the --voice flag beats everything.
	Voice map[string]map[string]string `toml:"voice"`

	// Wrap configures `talk wrap`.
	Wrap Wrap `toml:"wrap"`

	// QuietHours is the quiet window "HH:MM-HH:MM" in local time (may span
	// midnight, for example "18:00-08:00"); empty = disabled. Deliberately
	// no default window: a law that discards by time of day would silence
	// every evening cron job; quiet hours are opt-in like mute.
	QuietHours string `toml:"quiet_hours"`

	// QuietMode is the behaviour during quiet hours: "discard" (default,
	// drop silently) or "toast" (desktop notification instead of audio).
	QuietMode string `toml:"quiet_mode"`
}

// Audio configures playback.
type Audio struct {
	// Sink selects playback: "oto" (embedded playback, default) or "null"
	// (discard; CI, servers, tests).
	Sink string `toml:"sink"`
}

// Server holds the daemon's network settings (loopback only; the daemon
// binds 127.0.0.1, the config only supplies the port).
type Server struct {
	// Port of the daemon's HTTP server on 127.0.0.1: `[server] port = 7800`,
	// env override TALK_PORT, default 7800.
	Port int `toml:"port"`

	// AllowedOrigins is the CORS allow-list for POST /speak: exact origins
	// such as "https://chat.example.com". The entry "*" allows every origin
	// explicitly. Deliberate default: EMPTY, meaning no CORS headers at all
	// and the server-side origin guard rejects browser requests; the door
	// stays shut until configured (env TALK_ALLOWED_ORIGINS, comma-separated;
	// "off" clears it).
	AllowedOrigins []string `toml:"allowed_origins"`
}

// Daemon holds the background process settings (TOML `[daemon]`).
type Daemon struct {
	// Autostart lets talk start the daemon itself in the background on the
	// first speak command (default true; env TALK_AUTOSTART). false is for
	// setups that manage the daemon themselves (systemd, launchd, Task
	// Scheduler): without a daemon, say then speaks directly, with a note.
	Autostart bool `toml:"autostart"`
}

// Wrap holds the `talk wrap` settings (TOML `[wrap]`).
type Wrap struct {
	// Label replaces the command's base name in the announcement, for
	// example `label = "Deployment"` to hear "Deployment succeeded" instead
	// of "terraform succeeded" (env override TALK_WRAP_LABEL).
	Label string `toml:"label"`
}

// Queue holds the daemon's anti-spam laws (TOML `[queue]`).
type Queue struct {
	// RateLimit is the minimum gap between two announcement starts, as a
	// duration string ("30s"; "0s" = unlimited). Default 30 s.
	RateLimit time.Duration `toml:"rate_limit"`

	// AllowHighBurst lets priority=high deliberately break the rate limit
	// (default true). Quiet hours still apply.
	AllowHighBurst bool `toml:"allow_high_burst"`

	// MaxText caps announcement length in characters; longer texts are cut
	// at a word boundary (default 400; 0 = unlimited; env TALK_MAX_TEXT).
	MaxText int `toml:"max_text"`

	// MaxAge is the longest an announcement may wait in the queue; older
	// ones are discarded when they come due (default "2m"; "0s" =
	// unlimited; env TALK_MAX_AGE).
	MaxAge time.Duration `toml:"max_age"`
}

// ProviderSettings are the per-provider endpoint and model (TOML
// `[providers.<name>]`). Empty = built-in defaults; the env overrides
// TALK_ELEVENLABS_ENDPOINT / TALK_OPENAI_ENDPOINT / TALK_EDGE_ENDPOINT
// (read by the provider layer) beat the file. Keys come exclusively from
// TALK_ELEVENLABS_KEY / TALK_OPENAI_KEY and are never written to the file.
type ProviderSettings struct {
	Endpoint string `toml:"endpoint"`
	Model    string `toml:"model"` // openai only (default "tts-1")
}

// Defaults returns the built-in default configuration (the lowest layer).
func Defaults() Config {
	return Config{
		Audio:     Audio{Sink: SinkOto},
		Server:    Server{Port: DefaultServerPort},
		Queue:     Queue{RateLimit: DefaultRateLimit, AllowHighBurst: true, MaxText: DefaultMaxText, MaxAge: DefaultMaxAge},
		Daemon:    Daemon{Autostart: true},
		Lang:      DefaultLang,
		QuietMode: queue.QuietModeDiscard,
	}
}

// Options controls Load. Every field is injectable so unit tests run without
// a real HOME, environment or files.
type Options struct {
	// File overrides the platform-native path of config.toml (tests inject
	// a temp file). Empty: Dir() + "config.toml".
	File string

	// Getenv supplies environment variables (default os.Getenv): the TALK_*
	// overrides and the path resolution (HOME, XDG_CONFIG_HOME, APPDATA).
	Getenv func(string) string
}

// Load resolves the configuration in layers: defaults → config.toml (if
// present) → env overrides (TALK_* beats the file). Env and file validation
// errors are reported clearly, never ignored. If the config directory
// cannot be determined (no HOME), talk runs with defaults + env: the file is
// optional, a broken environment must not make talk unusable.
func Load(opts Options) (Config, error) {
	if opts.Getenv == nil {
		opts.Getenv = os.Getenv
	}
	cfg := Defaults()

	path := opts.File
	if path == "" {
		dir, err := Dir(opts.Getenv)
		if err != nil {
			return applyEnv(cfg, opts.Getenv)
		}
		path = filepath.Join(dir, fileName)
	}

	if _, err := toml.DecodeFile(path, &cfg); err != nil {
		if !errors.Is(err, os.ErrNotExist) {
			return cfg, fmt.Errorf("config %s: %w", path, err)
		}
	}
	return applyEnv(cfg, opts.Getenv)
}

// applyEnv applies the env overrides and validates the result.
func applyEnv(cfg Config, getenv func(string) string) (Config, error) {
	if v := getenv("TALK_AUDIO_SINK"); v != "" {
		cfg.Audio.Sink = v
	}
	if v := getenv("TALK_PROVIDER"); v != "" {
		cfg.Provider = v
	}
	if v := getenv("TALK_LANG"); v != "" {
		cfg.Lang = v
	}
	if v := getenv("TALK_PORT"); v != "" {
		port, err := strconv.Atoi(v)
		if err != nil || port < 1 || port > 65535 {
			return cfg, fmt.Errorf("TALK_PORT: invalid value %q (1–65535)", v)
		}
		cfg.Server.Port = port
	}
	if v := getenv("TALK_ALLOWED_ORIGINS"); v != "" {
		if v == "off" {
			cfg.Server.AllowedOrigins = nil
		} else {
			origins, err := splitOrigins(v)
			if err != nil {
				return cfg, fmt.Errorf("TALK_ALLOWED_ORIGINS: %w", err)
			}
			cfg.Server.AllowedOrigins = origins
		}
	}
	if v := getenv("TALK_MAX_TEXT"); v != "" {
		n, err := strconv.Atoi(v)
		if err != nil || n < 0 {
			return cfg, fmt.Errorf("TALK_MAX_TEXT: invalid value %q (characters; 0 = unlimited)", v)
		}
		cfg.Queue.MaxText = n
	}
	if v := getenv("TALK_MAX_AGE"); v != "" {
		d, err := time.ParseDuration(v)
		if err != nil || d < 0 {
			return cfg, fmt.Errorf("TALK_MAX_AGE: invalid value %q (duration such as \"2m\"; \"0s\" = unlimited)", v)
		}
		cfg.Queue.MaxAge = d
	}
	if v := getenv("TALK_AUTOSTART"); v != "" {
		b, err := strconv.ParseBool(v)
		if err != nil {
			return cfg, fmt.Errorf("TALK_AUTOSTART: invalid value %q (true/false)", v)
		}
		cfg.Daemon.Autostart = b
	}
	if v := getenv("TALK_WRAP_LABEL"); v != "" {
		cfg.Wrap.Label = v
	}
	if v := getenv("TALK_RATE_LIMIT"); v != "" {
		d, err := time.ParseDuration(v)
		if err != nil || d < 0 {
			return cfg, fmt.Errorf("TALK_RATE_LIMIT: invalid value %q (duration such as \"30s\"; \"0s\" = unlimited)", v)
		}
		cfg.Queue.RateLimit = d
	}
	if v := getenv("TALK_ALLOW_HIGH_BURST"); v != "" {
		b, err := strconv.ParseBool(v)
		if err != nil {
			return cfg, fmt.Errorf("TALK_ALLOW_HIGH_BURST: invalid value %q (true/false)", v)
		}
		cfg.Queue.AllowHighBurst = b
	}
	if v := getenv("TALK_QUIET_HOURS"); v != "" {
		if v == "off" {
			cfg.QuietHours = ""
		} else {
			if _, err := queue.ParseQuietHours(v); err != nil {
				return cfg, fmt.Errorf("TALK_QUIET_HOURS: invalid window %q (HH:MM-HH:MM, \"off\" = disabled)", v)
			}
			cfg.QuietHours = v
		}
	}
	if v := getenv("TALK_QUIET_MODE"); v != "" {
		if v != queue.QuietModeDiscard && v != queue.QuietModeToast {
			return cfg, fmt.Errorf("TALK_QUIET_MODE: invalid value %q (allowed: %q, %q)",
				v, queue.QuietModeDiscard, queue.QuietModeToast)
		}
		cfg.QuietMode = v
	}
	if cfg.Queue.MaxText < 0 || cfg.Queue.MaxAge < 0 || cfg.Queue.RateLimit < 0 {
		return cfg, fmt.Errorf("queue: max_text, max_age and rate_limit must not be negative (0 = unlimited)")
	}
	switch cfg.Audio.Sink {
	case SinkOto, SinkNull:
	default:
		return cfg, fmt.Errorf("audio.sink: invalid value %q (allowed: %q, %q)",
			cfg.Audio.Sink, SinkOto, SinkNull)
	}
	if cfg.Lang != "de" && cfg.Lang != "en" {
		return cfg, fmt.Errorf("lang: invalid value %q (allowed: de, en)", cfg.Lang)
	}
	// Validate allowed_origins from the file (env was parsed above): an empty
	// list is fine (door shut), but entries must have substance.
	for _, o := range cfg.Server.AllowedOrigins {
		if strings.TrimSpace(o) == "" {
			return cfg, fmt.Errorf("server.allowed_origins: empty entry in %v", cfg.Server.AllowedOrigins)
		}
	}
	// Validate quiet_hours from the file (env was checked above) and lift an
	// empty quiet_mode to the default.
	if cfg.QuietHours != "" {
		if _, err := queue.ParseQuietHours(cfg.QuietHours); err != nil {
			return cfg, err
		}
	}
	if cfg.QuietMode == "" {
		cfg.QuietMode = queue.QuietModeDiscard
	}
	return cfg, nil
}

// splitOrigins splits a comma-separated origin list (the env form of
// server.allowed_origins, for example "https://a.example, https://b.example").
// Whitespace around entries is tolerated; empty entries are an error.
func splitOrigins(v string) ([]string, error) {
	parts := strings.Split(v, ",")
	origins := make([]string, 0, len(parts))
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if p == "" {
			return nil, fmt.Errorf("empty entry in %q (comma-separated origins, or \"off\")", v)
		}
		origins = append(origins, p)
	}
	return origins, nil
}