package wireguard

import (
	"io/fs"
	"log"

	"asciigoat.org/ini/basic"
	"darvaza.org/core"
)

type sectionHandler func(*Config, *basic.Section) error

var sectionMap = map[string]func(*Config, *basic.Section) error{
	"Interface": loadInterfaceConfSection,
	"Peer":      loadPeerConfSection,
}

func loadConfSection(out *Config, src *basic.Section) error {
	h, ok := sectionMap[src.Key]
	if !ok {
		return core.Wrap(fs.ErrInvalid, "unknown section %q", src.Key)
	}

	return h(out, src)
}

func loadInterfaceConfSection(out *Config, src *basic.Section) error {
	var cfg InterfaceConfig

	for _, field := range src.Fields {
		if err := loadInterfaceConfField(&cfg, field); err != nil {
			return core.Wrap(err, "Interface")
		}
	}

	out.Interface = cfg
	return nil
}

func loadPeerConfSection(out *Config, src *basic.Section) error {
	var cfg PeerConfig

	for _, field := range src.Fields {
		if err := loadPeerConfField(&cfg, field); err != nil {
			return core.Wrap(err, "Peer[%v]", len(out.Peer))
		}
	}

	out.Peer = append(out.Peer, cfg)
	return nil
}

func configFieldHandler(vi any, key, value string) error

func loadInterfaceConfField(cfg *InterfaceConfig, field basic.Field) error {
	log.Printf("%s[%q] = %q", "Interface", field.Key, field.Value)

	key, value := field.Key, field.Value

	switch key {
	case "Address":
		return configFieldHandler(&cfg.Address, key, value)
	case "PrivateKey":
		return configFieldHandler(&cfg.PrivateKey, key, value)
	case "ListenPort":
		return configFieldHandler(&cfg.ListenPort, key, value)
	default:
		return core.Wrap(fs.ErrInvalid, "unknown field %q", key)
	}
}

func loadPeerConfField(cfg *PeerConfig, field basic.Field) error {
	log.Printf("%s[%q] = %q", "Peer", field.Key, field.Value)

	key, value := field.Key, field.Value

	switch key {
	case "PublicKey":
		return configFieldHandler(&cfg.PublicKey, key, value)
	case "Endpoint":
		return configFieldHandler(&cfg.Endpoint, key, value)
	case "AllowedIPs":
		return configFieldHandler(&cfg.AllowedIPs, key, value)
	default:
		return core.Wrap(fs.ErrInvalid, "unknown field %q", field.Key)
	}
}

func newConfigFromDocument(doc *basic.Document) (*Config, error) {
	var out Config

	if len(doc.Global) > 0 {
		err := core.Wrap(fs.ErrInvalid, "fields before the first section")
		return nil, err
	}

	for i := range doc.Sections {
		src := &doc.Sections[i]
		if err := loadConfSection(&out, src); err != nil {
			return nil, err
		}
	}

	return &out, nil
}