JSONObject.swift

import Foundation

/// Class for handling errors related to the parent class.
///
public enum JSONValidationErrors: ErrorType, CustomDebugStringConvertible, CustomStringConvertible {
    case ExpectedDictionary
    case ExpectedArray
    case MissingKey(String)
    case MissingIndex(Int)
    case ConversionFailed(String)
    case DateConversionFailed(String)

    func localizedFailureReason() -> String {
        switch self {
        case .ExpectedDictionary:
            return NSLocalizedString("Expected to find Dictionary in JSON response.",
                comment: "Error message to show when reading from a JSON object and a expected dictionary is not found.")
        case .ExpectedArray:
            return NSLocalizedString("Expected to find Array in JSON response.",
                comment: "Error message to show when reading from a JSON object and a expected array is not found.")
        case MissingKey(let key):
                return NSString(format:NSLocalizedString("Missing \"%@\" element in JSON response.",
                    comment: "Error message to show when parsing a JSON dictionary and a expected key is not found."),
                    "\(key)") as String
        case ConversionFailed(let key):
            return NSString(format:NSLocalizedString("Failed to convert object to %@ type.",
                comment: "Error message to show when converstion to a expected type failed."),
                "\(key)") as String
        case DateConversionFailed(let key):
                return NSString(format:NSLocalizedString("Failed to convert %@ to date.",
                    comment: "Error message to show when parsing a JSON dictionary field where a date was expected but the parsing failed."),
                    "\(key)") as String
        case MissingIndex(let index):
            return NSString(format:NSLocalizedString("Missing \"%i\" element in response array.",
                comment:"Error message to show when parsing a JSON array and an expected index is not found."),
                index) as String
        }
    }


    public func convertToNSError() -> NSError {
        let userInfo = [NSLocalizedFailureReasonErrorKey: self.localizedFailureReason()]
        return NSError(domain: "JSONValidationErrors", code: self._code, userInfo: userInfo)
    }

    public var description: String { get { return localizedFailureReason() }}

    public var debugDescription: String { get { return localizedFailureReason() }}
}

public class JSONObject: SequenceType {

    let json: AnyObject?

    public convenience init(url: NSURL) throws {
        let data = try NSData(contentsOfURL: url, options: NSDataReadingOptions())
        try self.init(data: data)
    }

    public convenience init(data: NSData) throws {
        let object = try NSJSONSerialization.JSONObjectWithData(data,  options: NSJSONReadingOptions())
        self.init(json: object)
    }

    public init(json: AnyObject?) {
        self.json = json
    }

    public func dictionary() throws -> [String: AnyObject] {
        guard let dictionary = json as? [String: AnyObject] else {
            throw JSONValidationErrors.ExpectedDictionary
        }
        return dictionary
    }

    public func array() throws -> [AnyObject] {
        guard let array = json as? [AnyObject] else {
            throw JSONValidationErrors.ExpectedArray
        }
        return array
    }

    public func string() throws -> String {
        guard let result = json as? String else {
            throw JSONValidationErrors.ConversionFailed("String")
        }
        return result
    }

    public func integer() throws -> Int {
        guard let result = json as? Int else {
            throw JSONValidationErrors.ConversionFailed("Int")
        }
        return result
    }

    public func double() throws -> Double {
        guard let result = json as? Double else {
            throw JSONValidationErrors.ConversionFailed("Double")
        }
        return result
    }

    public func bool() throws -> Bool {
        guard let result = json as? Bool else {
            throw JSONValidationErrors.ConversionFailed("Bool")
        }
        return result
    }

    public func null() throws -> NSNull {
        guard let result = json as? NSNull else {
                throw JSONValidationErrors.ConversionFailed("NSNull")
            }
        return result;
    }

    public func dictionary(key: String) throws -> JSONObject {
        guard let dictionary = json as? [String: AnyObject] else {
            throw JSONValidationErrors.ExpectedDictionary
        }
        guard let obj = dictionary[key] else {
            throw JSONValidationErrors.MissingKey(key)
        }

        return JSONObject(json: obj)
    }

    public func array(index: Int) throws -> JSONObject {
        guard let array = json as? [AnyObject] else {
            throw JSONValidationErrors.ExpectedArray
        }

        guard (index >= 0) && (index < array.count) else {
                throw JSONValidationErrors.MissingIndex(index)
        }

        let obj = array[index]

        return JSONObject(json: obj)
    }

    public func dateWithFormatter(dateFormatter: NSDateFormatter) throws -> NSDate {

        let dateString = try self.string() as String
        guard let date = dateFormatter.dateFromString(dateString) else {
            throw JSONValidationErrors.DateConversionFailed("")
        }

        return date
    }

    public func generate() -> IndexingGenerator<[JSONObject]> {
        if let array = json as? [AnyObject] {
            return array.map({ (obj) -> JSONObject in
                JSONObject(json:obj)
            }).generate()
        }
        if let dictionary = json as? [String:AnyObject] {
            return dictionary.map({ (obj) -> JSONObject in
                JSONObject(json:obj.0)
            }).generate()
        }
        return Array<JSONObject>().generate()
    }
}