// Package config loads the Control Service configuration from the process
// environment. Every secret comes from the environment (environment.d); nothing
// is compiled into the binary and nothing is read from a committed file.
package config

import (
	"errors"
	"fmt"
	"log/slog"
	"os"
	"strconv"
	"strings"
	"time"
	// Embed the IANA time zone database so CONTROL_TIMEZONE resolves even in a
	// container without tzdata, such as the test image.
	_ "time/tzdata"
)

// Config is the fully resolved runtime configuration.
type Config struct {
	// Addr is the listen address, for example ":8791".
	Addr string
	// DBPath is the SQLite database file, for example "/data/control.db".
	DBPath string
	// SessionSecret signs the session cookie. Required, >= 16 bytes.
	SessionSecret []byte
	// AdminUsername is the single dashboard login name (Sam).
	AdminUsername string
	// AdminPassword is the plaintext password. Optional if AdminPasswordHash is set.
	AdminPassword string
	// AdminPasswordHash is a bcrypt hash. Optional if AdminPassword is set.
	AdminPasswordHash string
	// AdminAPIToken authenticates the versioned admin API (Phase 8). It is
	// separate from the session login and comes from environment.d. When it is
	// empty the admin API answers 503 and nothing else changes.
	AdminAPIToken string
	// DeviceKeycodeHash is a bcrypt hash of the shared device keycode (Phase 8).
	// It is optional: the code is seeded into SQLite at start-up and can be
	// changed at runtime with `control keycode`. It is never stored in plaintext
	// and never logged.
	DeviceKeycodeHash string
	// CookieSecure sets the Secure attribute on cookies. Keep true behind HTTPS.
	CookieSecure bool
	// SessionTTL is how long a session cookie stays valid.
	SessionTTL time.Duration
	// LogLevel is the slog level.
	LogLevel slog.Level
	// AppEnv is a label such as "production" or "development".
	AppEnv string
	// Version is injected at build time.
	Version string
	// ScheduleLocation is the timezone weekly schedule windows are evaluated in
	// (CONTROL_TIMEZONE). Windows are wall-clock, so this must be the family's
	// zone, not the container's default of UTC. It defaults to
	// DefaultTimezone.
	ScheduleLocation *time.Location

	// MQTTEnabled turns the broker link on. When false the service runs
	// HTTP-only and never touches the broker.
	MQTTEnabled bool
	// MQTTBroker is the broker URL, for example "tls://mosquitto:8883" or
	// "tcp://127.0.0.1:1883".
	MQTTBroker string
	// MQTTClientID is the MQTT client id of the Control Service.
	MQTTClientID string
	// MQTTUsername and MQTTPassword are the Control Service credentials
	// (AGENTS.md §10 rule 6: per-device credentials).
	MQTTUsername string
	MQTTPassword string
	// MQTTCAFile is the PEM bundle used to verify the broker certificate.
	MQTTCAFile string
	// MQTTInsecure allows a plaintext, credential-less broker link. It exists
	// only until the shared Mosquitto gets the TLS listener; never set it in
	// production.
	MQTTInsecure bool
}

// Load reads and validates the configuration.
func Load() (*Config, error) {
	cfg := &Config{
		Addr:              env("CONTROL_ADDR", ":8791"),
		DBPath:            env("CONTROL_DB_PATH", "/data/control.db"),
		AdminUsername:     env("CONTROL_ADMIN_USERNAME", "sam"),
		AdminPassword:     os.Getenv("CONTROL_ADMIN_PASSWORD"),
		AdminPasswordHash: os.Getenv("CONTROL_ADMIN_PASSWORD_HASH"),
		AdminAPIToken:     os.Getenv("CONTROL_ADMIN_API_TOKEN"),
		DeviceKeycodeHash: os.Getenv("CONTROL_DEVICE_KEYCODE_HASH"),
		CookieSecure:      envBool("CONTROL_COOKIE_SECURE", true),
		AppEnv:            env("CONTROL_APP_ENV", "production"),
		MQTTEnabled:       envBool("CONTROL_MQTT_ENABLED", true),
		MQTTBroker:        env("CONTROL_MQTT_BROKER", DefaultMQTTBroker),
		MQTTClientID:      env("CONTROL_MQTT_CLIENT_ID", "control-service"),
		MQTTUsername:      os.Getenv("CONTROL_MQTT_USERNAME"),
		MQTTPassword:      os.Getenv("CONTROL_MQTT_PASSWORD"),
		MQTTCAFile:        env("CONTROL_MQTT_CA_FILE", "/etc/webrestrict/tls/ca.crt"),
		MQTTInsecure:      envBool("CONTROL_MQTT_INSECURE", false),
	}

	secret := os.Getenv("CONTROL_SESSION_SECRET")
	if len(secret) < 16 {
		return nil, errors.New("CONTROL_SESSION_SECRET must be set and at least 16 characters")
	}
	cfg.SessionSecret = []byte(secret)

	if cfg.AdminPassword == "" && cfg.AdminPasswordHash == "" {
		return nil, errors.New("set CONTROL_ADMIN_PASSWORD or CONTROL_ADMIN_PASSWORD_HASH")
	}
	if cfg.AdminUsername == "" {
		return nil, errors.New("CONTROL_ADMIN_USERNAME must not be empty")
	}

	ttl, err := time.ParseDuration(env("CONTROL_SESSION_TTL", "12h"))
	if err != nil {
		return nil, fmt.Errorf("CONTROL_SESSION_TTL: %w", err)
	}
	cfg.SessionTTL = ttl

	lvl, err := parseLevel(env("CONTROL_LOG_LEVEL", "info"))
	if err != nil {
		return nil, err
	}
	cfg.LogLevel = lvl

	loc, err := time.LoadLocation(env("CONTROL_TIMEZONE", DefaultTimezone))
	if err != nil {
		return nil, fmt.Errorf("CONTROL_TIMEZONE: %w", err)
	}
	cfg.ScheduleLocation = loc

	if err := cfg.validateMQTT(); err != nil {
		return nil, err
	}

	return cfg, nil
}

// DefaultMQTTBroker is where the shared Mosquitto on `.13` lives, as seen from
// inside this project's container. The compose file maps host.docker.internal
// to the host gateway.
const DefaultMQTTBroker = "tcp://host.docker.internal:1883"

// DefaultTimezone is the schedule timezone used when CONTROL_TIMEZONE is unset.
// It matches the lab host's configured zone; set CONTROL_TIMEZONE to override.
const DefaultTimezone = "Australia/Sydney"

// MQTTTLS reports whether the broker URL asks for TLS.
func (c *Config) MQTTTLS() bool {
	return strings.HasPrefix(c.MQTTBroker, "tls://") || strings.HasPrefix(c.MQTTBroker, "ssl://")
}

// validateMQTT refuses a link that carries neither TLS nor credentials, unless
// CONTROL_MQTT_INSECURE explicitly allows it (AGENTS.md §10 rule 6).
func (c *Config) validateMQTT() error {
	if !c.MQTTEnabled {
		return nil
	}
	if c.MQTTBroker == "" {
		return errors.New("CONTROL_MQTT_BROKER must not be empty when MQTT is enabled")
	}
	if c.MQTTUsername == "" || c.MQTTPassword == "" {
		if !c.MQTTInsecure {
			return errors.New("CONTROL_MQTT_USERNAME and CONTROL_MQTT_PASSWORD are required; " +
				"set CONTROL_MQTT_INSECURE=true only for the pre-TLS lab broker")
		}
	}
	if !c.MQTTTLS() && !c.MQTTInsecure {
		return errors.New("CONTROL_MQTT_BROKER must use tls:// (AGENTS.md §10 rule 6); " +
			"set CONTROL_MQTT_INSECURE=true only for the pre-TLS lab broker")
	}
	return nil
}

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

func envBool(key string, fallback bool) bool {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return fallback
	}
	b, err := strconv.ParseBool(v)
	if err != nil {
		return fallback
	}
	return b
}

func parseLevel(s string) (slog.Level, error) {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "debug":
		return slog.LevelDebug, nil
	case "info", "":
		return slog.LevelInfo, nil
	case "warn", "warning":
		return slog.LevelWarn, nil
	case "error":
		return slog.LevelError, nil
	default:
		return 0, fmt.Errorf("CONTROL_LOG_LEVEL: unknown level %q", s)
	}
}