// Package config parses the clip-sync TOML configuration file and applies
// environment variable overrides.
//
// Config file location: ~/.config/clip-sync/peers.toml (overridable with
// the --config flag). Environment overrides:
//
//	CLIP_SYNC_PORT            — override daemon.port
//	CLIP_SYNC_POLL_MS         — override daemon.poll_interval_ms
//	CLIP_SYNC_KEY             — override security.shared_key
//	CLIP_SYNC_MAX_BODY_BYTES  — override daemon.max_body_bytes
package config

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

	"github.com/BurntSushi/toml"
)

// Config represents the full clip-sync configuration.
type Config struct {
	Daemon   DaemonConfig   `toml:"daemon"`
	Security SecurityConfig `toml:"security"`
	Peers    []PeerConfig   `toml:"peers"`
}

// DaemonConfig holds daemon-level settings.
type DaemonConfig struct {
	Port           int    `toml:"port"`
	PollIntervalMs int    `toml:"poll_interval_ms"`
	MaxBodyBytes   int64  `toml:"max_body_bytes"`
	HistorySize    int    `toml:"history_size"`
	Discovery      bool   `toml:"discovery"`
	Notify         bool   `toml:"notify"`
	SyncImages     bool   `toml:"sync_images"`
	ReceiveFiles   bool   `toml:"receive_files"`
	ReceiveDir     string `toml:"receive_dir"`
}

// SecurityConfig holds peer authentication and transport security settings.
type SecurityConfig struct {
	SharedKey          string   `toml:"shared_key"`
	AllowedOrigins     []string `toml:"allowed_origins"`
	TLS                bool     `toml:"tls"`
	CertFile           string   `toml:"cert_file"`
	KeyFile            string   `toml:"key_file"`
	InsecureSkipVerify bool     `toml:"insecure_skip_verify"`
}

// PeerConfig represents one remote clip-sync peer.
type PeerConfig struct {
	Name string `toml:"name"`
	Addr string `toml:"addr"`
	TLS  bool   `toml:"tls"` // per-peer override of security.tls
}

// Default values.
const (
	DefaultPort           = 9137
	DefaultPollIntervalMs = 500
	DefaultMaxBodyBytes   = 10 << 20 // 10 MiB
	DefaultHistorySize    = 50
	ConfigDir             = ".config/clip-sync"
	ConfigFile            = "peers.toml"
)

// DefaultConfigPath returns the default config file path (~/.config/clip-sync/peers.toml).
func DefaultConfigPath() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("config: cannot find home directory: %w", err)
	}
	return filepath.Join(home, ConfigDir, ConfigFile), nil
}

// DefaultCertFile returns the default TLS certificate path.
func DefaultCertFile() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("config: cannot find home directory: %w", err)
	}
	return filepath.Join(home, ConfigDir, "cert.pem"), nil
}

// DefaultKeyFile returns the default TLS private key path.
func DefaultKeyFile() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("config: cannot find home directory: %w", err)
	}
	return filepath.Join(home, ConfigDir, "key.pem"), nil
}

// Load reads the config file from the default location and applies
// environment variable overrides.
func Load() (*Config, error) {
	path, err := DefaultConfigPath()
	if err != nil {
		return nil, err
	}
	return LoadFrom(path)
}

// LoadFrom reads the config file at the given path and applies environment
// variable overrides. If the file does not exist, defaults are used.
func LoadFrom(path string) (*Config, error) {
	cfg := &Config{
		Daemon: DaemonConfig{
			Port:           DefaultPort,
			PollIntervalMs: DefaultPollIntervalMs,
			MaxBodyBytes:   DefaultMaxBodyBytes,
			HistorySize:    DefaultHistorySize,
		},
	}

	if _, err := toml.DecodeFile(path, cfg); err != nil {
		if !os.IsNotExist(err) {
			return nil, fmt.Errorf("config: cannot parse %s: %w", path, err)
		}
		// File doesn't exist — use defaults (no peers configured).
	}

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

	return cfg, nil
}

func applyEnvOverrides(cfg *Config) error {
	if v := os.Getenv("CLIP_SYNC_PORT"); v != "" {
		port, err := strconv.Atoi(v)
		if err != nil {
			return fmt.Errorf("config: invalid CLIP_SYNC_PORT: %w", err)
		}
		cfg.Daemon.Port = port
	}

	if v := os.Getenv("CLIP_SYNC_POLL_MS"); v != "" {
		ms, err := strconv.Atoi(v)
		if err != nil {
			return fmt.Errorf("config: invalid CLIP_SYNC_POLL_MS: %w", err)
		}
		cfg.Daemon.PollIntervalMs = ms
	}

	if v := os.Getenv("CLIP_SYNC_KEY"); v != "" {
		cfg.Security.SharedKey = v
	}

	if v := os.Getenv("CLIP_SYNC_MAX_BODY_BYTES"); v != "" {
		n, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			return fmt.Errorf("config: invalid CLIP_SYNC_MAX_BODY_BYTES: %w", err)
		}
		cfg.Daemon.MaxBodyBytes = n
	}

	return nil
}

// PollInterval returns the poll interval as a time.Duration.
func (c *Config) PollInterval() time.Duration {
	return time.Duration(c.Daemon.PollIntervalMs) * time.Millisecond
}

// ListenAddr returns the HTTP listen address for this daemon.
func (c *Config) ListenAddr() string {
	return fmt.Sprintf(":%d", c.Daemon.Port)
}

// MaxBodyBytes returns the effective request body size limit, clamped to a
// sane minimum so a zero/negative config value never disables the limit.
func (c *Config) MaxBodyBytes() int64 {
	if c.Daemon.MaxBodyBytes > 0 {
		return c.Daemon.MaxBodyBytes
	}
	return DefaultMaxBodyBytes
}

// ReceiveDir returns the directory where received files are written, resolving
// the default (~/Downloads/clip-sync) when not configured.
func (c *Config) ReceiveDir() string {
	if c.Daemon.ReceiveDir != "" {
		return c.Daemon.ReceiveDir
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "clip-sync-received"
	}
	return filepath.Join(home, "Downloads", "clip-sync")
}