package cfg

import (
	"encoding/json"
	"fmt"
	"strings"

	"github.com/pelletier/go-toml/v2"
	"github.com/philandstuff/dhall-golang/v6"
	"github.com/sblinch/kdl-go"
	"github.com/tailscale/hujson"
	"go.jolheiser.com/nixfig"
	"gopkg.in/yaml.v3"
)

// Encoding is a type of configuration encoding
type Encoding string

const (
	JSON  Encoding = "json"
	JSONC Encoding = "jsonc"
	YAML  Encoding = "yaml"
	TOML  Encoding = "toml"
	NIX   Encoding = "nix"
	DHALL Encoding = "dhall"
	KDL   Encoding = "kdl"
)

// Marshal takes data and encodes for an [Encoding]
func (e Encoding) Marshal(v any) ([]byte, error) {
	return Marshal(e, v)
}

// Unmarshal decodes data for an [Encoding]
func (e Encoding) Unmarshal(data []byte, v any) error {
	return Unmarshal(e, data, v)
}

// ParseEncoding parses a string into an [Encoding]
func ParseEncoding(s string) (Encoding, error) {
	switch strings.ToLower(s) {
	case "json":
		return JSON, nil
	case "jsonc":
		return JSONC, nil
	case "yaml":
		return YAML, nil
	case "toml":
		return TOML, nil
	case "nix":
		return NIX, nil
	case "dhall":
		return DHALL, nil
	case "kdl":
		return KDL, nil
	default:
		return "", fmt.Errorf("unknown encoding %q", s)
	}
}

// Marshal is a top-level helper for encoding data
func Marshal(e Encoding, v any) ([]byte, error) {
	switch e {
	case JSON, JSONC:
		return json.MarshalIndent(v, "", "\t")
	case YAML:
		return yaml.Marshal(v)
	case TOML:
		return toml.Marshal(v)
	case NIX:
		if nixfig.Fmt != nil {
			return nixfig.MarshalFormat(v)
		}
		return nixfig.Marshal(v)
	case KDL:
		return kdl.Marshal(v)
	default:
		return nil, fmt.Errorf("unknown marshal format %q", e)
	}
}

// Unmarshal is a top-level helper for decoding data
func Unmarshal(e Encoding, data []byte, v any) error {
	switch e {
	case JSON, JSONC:
		b, err := hujson.Standardize(data)
		if err != nil {
			return err
		}
		return json.Unmarshal(b, v)
	case YAML:
		return yaml.Unmarshal(data, v)
	case TOML:
		return toml.Unmarshal(data, v)
	case NIX:
		return nixfig.Unmarshal(data, v)
	case DHALL:
		return dhall.Unmarshal(data, v)
	case KDL:
		return kdl.Unmarshal(data, v)
	default:
		return fmt.Errorf("unknown unmarshal format %q", e)

	}
}