// Copyright (c) 2025-2026 Probo Inc <hello@probo.com>.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package cipher

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
)

type (
	EncryptionKey [32]byte
)

func (k EncryptionKey) Bytes() []byte {
	return k[:]
}

func (k *EncryptionKey) UnmarshalJSON(data []byte) error {
	var key string
	if err := json.Unmarshal(data, &key); err != nil {
		return err
	}

	return k.UnmarshalText([]byte(key))
}

func (k *EncryptionKey) UnmarshalText(text []byte) error {
	decoded, err := base64.StdEncoding.DecodeString(string(text))
	if err != nil {
		return fmt.Errorf("cannot decode base64 key: %w", err)
	}

	if len(decoded) != 32 {
		return fmt.Errorf("key must be 32 bytes for AES-256, got %d bytes after base64 decoding", len(decoded))
	}

	copy(k[:], decoded)

	return nil
}

func (k EncryptionKey) MarshalJSON() ([]byte, error) {
	return json.Marshal(base64.StdEncoding.EncodeToString(k[:]))
}

func Encrypt(data []byte, key EncryptionKey) ([]byte, error) {
	block, err := aes.NewCipher(key.Bytes())
	if err != nil {
		return nil, err
	}

	nonce := make([]byte, 12)
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return nil, err
	}

	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

	ciphertext := aesgcm.Seal(nonce, nonce, data, nil)

	return ciphertext, nil
}

func Decrypt(data []byte, key EncryptionKey) ([]byte, error) {
	block, err := aes.NewCipher(key.Bytes())
	if err != nil {
		return nil, err
	}

	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

	if len(data) < 12 {
		return nil, fmt.Errorf("ciphertext too short")
	}

	nonce, ciphertext := data[:12], data[12:]

	plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return nil, fmt.Errorf("cannot decrypt: %w", err)
	}

	return plaintext, nil
}