import Foundation

import MetaCodable

/// An `HelperCoder` that helps decoding/encoding

/// base64 data.

///

/// This type can be used to decode/encode base64 data

/// string and convert to `Data` type.

public struct Base64Coder: HelperCoder {

/// The options to use when decoding data.

private let decodeOptions: Data.Base64DecodingOptions

/// The options to use when encoding data.

private let encodeOptions: Data.Base64EncodingOptions

/// Creates a new instance of `HelperCoder` that decodes/encodes

/// base64 data.

///

/// - Parameters:

/// - decodeOptions: The options to use when decoding data.

/// - encodeOptions: The options to use when encoding data.

public init(

decodeOptions: Data.Base64DecodingOptions = [],

encodeOptions: Data.Base64EncodingOptions = []

) {

self.decodeOptions = decodeOptions

self.encodeOptions = encodeOptions

}

/// Decodes base64 data with provided decoding options

/// from the given `decoder`.

///

/// The data is decoded from a base64 string representation.

///

/// - Parameter decoder: The decoder to read data from.

/// - Returns: The data decoded.

///

/// - Throws: `DecodingError.typeMismatch` if the decoded string

/// isn't a valid base64 representation.

public func decode(from decoder: Decoder) throws -> Data {

let base64Str = try String(from: decoder)

guard let data = Data(base64Encoded: base64Str, options: decodeOptions)

else {

let errDesc = "Invalid base64 string \"\(base64Str)\""

throw DecodingError.typeMismatch(

Data.self,

.init(codingPath: decoder.codingPath, debugDescription: errDesc)

)

}

return data

}

/// Encodes base64 data with provided encoding options

/// to the given `decoder`.

///

/// The data is encoded as a base64 string representation.

///

/// - Parameters:

/// - value: The data to encode.

/// - encoder: The encoder to write data to.

public func encode(_ value: Data, to encoder: Encoder) throws {

let base64Str = value.base64EncodedString(options: encodeOptions)

try base64Str.encode(to: encoder)

}

}