package config

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"strings"

	log "github.com/sirupsen/logrus"
	"gopkg.in/yaml.v3"
)

// DefaultCodexLiveMediaMaxSessions is the default in-process media session limit.
const DefaultCodexLiveMediaMaxSessions = 32

// UnmarshalYAML supports the deprecated allow-private-remote-ips setting while
// preserving the default behavior of allowing private downstream candidates.
func (c *CodexLiveMediaRelayConfig) UnmarshalYAML(value *yaml.Node) error {
	type plain CodexLiveMediaRelayConfig
	var decoded plain
	if errDecode := value.Decode(&decoded); errDecode != nil {
		return errDecode
	}
	var allowPrivate *bool
	var disablePrivate *bool
	if value.Kind == yaml.MappingNode {
		for index := 0; index+1 < len(value.Content); index += 2 {
			key := value.Content[index].Value
			switch key {
			case "allow-private-remote-ips":
				var setting bool
				if errDecode := value.Content[index+1].Decode(&setting); errDecode != nil {
					return fmt.Errorf("decode codex.live-media-relay.allow-private-remote-ips: %w", errDecode)
				}
				allowPrivate = &setting
			case "disable-private-remote-ips":
				var setting bool
				if errDecode := value.Content[index+1].Decode(&setting); errDecode != nil {
					return fmt.Errorf("decode codex.live-media-relay.disable-private-remote-ips: %w", errDecode)
				}
				disablePrivate = &setting
			}
		}
	}
	if allowPrivate != nil && disablePrivate != nil {
		return errors.New("codex.live-media-relay cannot set both allow-private-remote-ips and disable-private-remote-ips")
	}
	if allowPrivate != nil {
		decoded.DisablePrivateRemoteIPs = !*allowPrivate
		log.Warn("codex.live-media-relay.allow-private-remote-ips is deprecated; use disable-private-remote-ips with the inverse value")
	}
	*c = CodexLiveMediaRelayConfig(decoded)
	return nil
}

// EffectiveMaxSessions returns the configured media session limit.
func (c CodexLiveMediaRelayConfig) EffectiveMaxSessions() int {
	if c.MaxSessions > 0 {
		return c.MaxSessions
	}
	return DefaultCodexLiveMediaMaxSessions
}

// Validate verifies the Codex Live media relay configuration.
func (c CodexLiveMediaRelayConfig) Validate() error {
	if !c.Enabled {
		return nil
	}
	if c.MaxSessions < 0 {
		return errors.New("codex.live-media-relay.max-sessions must not be negative")
	}
	if publicIP := strings.TrimSpace(c.PublicIP); publicIP != "" && net.ParseIP(publicIP) == nil {
		return fmt.Errorf("codex.live-media-relay.public-ip is invalid: %q", publicIP)
	}
	if (c.UDPPortMin == 0) != (c.UDPPortMax == 0) {
		return errors.New("codex.live-media-relay UDP port minimum and maximum must both be set")
	}
	if c.UDPPortMin > c.UDPPortMax {
		return errors.New("codex.live-media-relay.udp-port-min must not exceed udp-port-max")
	}
	if c.UDPPortMin != 0 {
		availablePorts := int(c.UDPPortMax) - int(c.UDPPortMin) + 1
		requiredPorts := c.EffectiveMaxSessions() * 2
		if availablePorts < requiredPorts {
			return fmt.Errorf("codex.live-media-relay UDP range requires at least %d ports for %d sessions", requiredPorts, c.EffectiveMaxSessions())
		}
	}
	for serverIndex, server := range c.ICEServers {
		if len(server.URLs) == 0 {
			return fmt.Errorf("codex.live-media-relay.ice-servers[%d].urls is required", serverIndex)
		}
		for _, rawURL := range server.URLs {
			parsed, errParse := url.Parse(strings.TrimSpace(rawURL))
			if errParse != nil || parsed.Scheme == "" {
				return fmt.Errorf("codex.live-media-relay.ice-servers[%d] contains an invalid URL", serverIndex)
			}
			switch strings.ToLower(parsed.Scheme) {
			case "stun", "stuns", "turn", "turns":
			default:
				return fmt.Errorf("codex.live-media-relay.ice-servers[%d] uses unsupported scheme %q", serverIndex, parsed.Scheme)
			}
		}
	}
	return nil
}