//
//  ParameterEncoding.swift
//
//  Copyright (c) 2014-2016 Alamofire Software Foundation (http://alamofire.org/)
//
//  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.
//

import Foundation

/**
    HTTP method definitions.

    See https://tools.ietf.org/html/rfc7231#section-4.3
*/
public enum Method: String {
    case OPTIONS, GET, HEAD, POST, PUT, PATCH, DELETE, TRACE, CONNECT
}

// MARK: ParameterEncoding

/**
    Used to specify the way in which a set of parameters are applied to a URL request.

    - `URL`:             Creates a query string to be set as or appended to any existing URL query for `GET`, `HEAD`, 
                         and `DELETE` requests, or set as the body for requests with any other HTTP method. The 
                         `Content-Type` HTTP header field of an encoded request with HTTP body is set to
                         `application/x-www-form-urlencoded; charset=utf-8`. Since there is no published specification
                         for how to encode collection types, the convention of appending `[]` to the key for array
                         values (`foo[]=1&foo[]=2`), and appending the key surrounded by square brackets for nested
                         dictionary values (`foo[bar]=baz`).

    - `URLEncodedInURL`: Creates query string to be set as or appended to any existing URL query. Uses the same
                         implementation as the `.URL` case, but always applies the encoded result to the URL.

    - `JSON`:            Uses `NSJSONSerialization` to create a JSON representation of the parameters object, which is 
                         set as the body of the request. The `Content-Type` HTTP header field of an encoded request is 
                         set to `application/json`.

    - `PropertyList`:    Uses `NSPropertyListSerialization` to create a plist representation of the parameters object,
                         according to the associated format and write options values, which is set as the body of the
                         request. The `Content-Type` HTTP header field of an encoded request is set to
                         `application/x-plist`.

    - `Custom`:          Uses the associated closure value to construct a new request given an existing request and
                         parameters.
*/
public enum ParameterEncoding {
    case url
    case urlEncodedInURL
    case json
    case propertyList(PropertyListSerialization.PropertyListFormat, PropertyListSerialization.WriteOptions)
    case custom((URLRequestConvertible, [String: AnyObject]?) -> (URLRequest, NSError?))

    /**
        Creates a URL request by encoding parameters and applying them onto an existing request.

        - parameter URLRequest: The request to have parameters applied.
        - parameter parameters: The parameters to apply.

        - returns: A tuple containing the constructed request and the error that occurred during parameter encoding, 
                   if any.
    */
    public func encode(
        _ URLRequest: URLRequestConvertible,
        parameters: [String: AnyObject]?)
        -> (Foundation.URLRequest, NSError?)
    {
        var urlRequest = URLRequest.urlRequest

        guard let parameters = parameters else { return (urlRequest, nil) }

        var encodingError: NSError? = nil

        switch self {
        case .url, .urlEncodedInURL:
            func query(_ parameters: [String: AnyObject]) -> String {
                var components: [(String, String)] = []

                for key in parameters.keys.sorted(isOrderedBefore: <) {
                    let value = parameters[key]!
                    components += queryComponents(key, value)
                }

                return (components.map { "\($0)=\($1)" } as [String]).joined(separator: "&")
            }

            func encodesParametersInURL(_ method: Method) -> Bool {
                switch self {
                case .urlEncodedInURL:
                    return true
                default:
                    break
                }

                switch method {
                case .GET, .HEAD, .DELETE:
                    return true
                default:
                    return false
                }
            }

            if let method = Method(rawValue: urlRequest.httpMethod!) where encodesParametersInURL(method) {
                if var
                    URLComponents = URLComponents(url: urlRequest.url!, resolvingAgainstBaseURL: false)
                    where !parameters.isEmpty
                {
                    let percentEncodedQuery = (URLComponents.percentEncodedQuery.map { $0 + "&" } ?? "") + query(parameters)
                    URLComponents.percentEncodedQuery = percentEncodedQuery
                    urlRequest.url = URLComponents.url
                }
            } else {
                if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
                    urlRequest.setValue(
                        "application/x-www-form-urlencoded; charset=utf-8",
                        forHTTPHeaderField: "Content-Type"
                    )
                }

                urlRequest.httpBody = query(parameters).data(
                    using: String.Encoding.utf8,
                    allowLossyConversion: false
                )
            }
        case .json:
            do {
                let options = JSONSerialization.WritingOptions()
                let data = try JSONSerialization.data(withJSONObject: parameters, options: options)

                if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
                    urlRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
                }

                urlRequest.httpBody = data
            } catch {
                encodingError = error as NSError
            }
        case .propertyList(let format, let options):
            do {
                let data = try PropertyListSerialization.data(
                    fromPropertyList: parameters,
                    format: format,
                    options: options
                )

                if urlRequest.value(forHTTPHeaderField: "Content-Type") == nil {
                    urlRequest.setValue("application/x-plist", forHTTPHeaderField: "Content-Type")
                }

                urlRequest.httpBody = data
            } catch {
                encodingError = error as NSError
            }
        case .custom(let closure):
            (urlRequest, encodingError) = closure(urlRequest, parameters)
        }

        return (urlRequest, encodingError)
    }

    /**
        Creates percent-escaped, URL encoded query string components from the given key-value pair using recursion.

        - parameter key:   The key of the query component.
        - parameter value: The value of the query component.

        - returns: The percent-escaped, URL encoded query string components.
    */
    public func queryComponents(_ key: String, _ value: AnyObject) -> [(String, String)] {
        var components: [(String, String)] = []

        if let dictionary = value as? [String: AnyObject] {
            for (nestedKey, value) in dictionary {
                components += queryComponents("\(key)[\(nestedKey)]", value)
            }
        } else if let array = value as? [AnyObject] {
            for value in array {
                components += queryComponents("\(key)[]", value)
            }
        } else {
            components.append((escape(key), escape("\(value)")))
        }

        return components
    }

    /**
        Returns a percent-escaped string following RFC 3986 for a query string key or value.

        RFC 3986 states that the following characters are "reserved" characters.

        - General Delimiters: ":", "#", "[", "]", "@", "?", "/"
        - Sub-Delimiters: "!", "$", "&", "'", "(", ")", "*", "+", ",", ";", "="

        In RFC 3986 - Section 3.4, it states that the "?" and "/" characters should not be escaped to allow
        query strings to include a URL. Therefore, all "reserved" characters with the exception of "?" and "/"
        should be percent-escaped in the query string.

        - parameter string: The string to be percent-escaped.

        - returns: The percent-escaped string.
    */
    public func escape(_ string: String) -> String {
        let generalDelimitersToEncode = ":#[]@" // does not include "?" or "/" due to RFC 3986 - Section 3.4
        let subDelimitersToEncode = "!$&'()*+,;="

        // rdar://26850776
        // Crash in Xcode 8 Seed 1 when trying to mutate a CharacterSet with remove
        var allowedCharacterSet = NSMutableCharacterSet.urlQueryAllowed()
        allowedCharacterSet.remove(charactersIn: "\(generalDelimitersToEncode)\(subDelimitersToEncode)")

        var escaped = ""

        //==========================================================================================================
        //
        //  Batching is required for escaping due to an internal bug in iOS 8.1 and 8.2. Encoding more than a few
        //  hundred Chinese characters causes various malloc error crashes. To avoid this issue until iOS 8 is no
        //  longer supported, batching MUST be used for encoding. This introduces roughly a 20% overhead. For more
        //  info, please refer to:
        //
        //      - https://github.com/Alamofire/Alamofire/issues/206
        //
        //==========================================================================================================

        if #available(iOS 8.3, OSX 10.10, *) {
            escaped = string.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) ?? string
        } else {
            let batchSize = 50
            var index = string.startIndex

            while index != string.endIndex {
                let startIndex = index
                let endIndex = string.index(index, offsetBy: batchSize, limitedBy: string.endIndex)
                let range = startIndex..<(endIndex ?? string.endIndex)

                let substring = string.substring(with: range)

                escaped += substring.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) ?? substring

                index = endIndex ?? string.endIndex
            }
        }

        return escaped
    }
}
