//
//  HttpParser.swift
//  Swifter
// 
//  Copyright (c) 2014-2016 Damian Kołakowski. All rights reserved.
//

import Foundation

enum HttpParserError: Error {
    case InvalidStatusLine(String)
}

public class HttpParser {
    
    public init() { }
    
    public func readHttpRequest(_ socket: Socket) throws -> HttpRequest {
        let statusLine = try socket.readLine()
        let statusLineTokens = statusLine.split(" ")
        if statusLineTokens.count < 3 {
            throw HttpParserError.InvalidStatusLine(statusLine)
        }
        let request = HttpRequest()
        request.method = statusLineTokens[0]
        request.path = statusLineTokens[1]
        request.queryParams = extractQueryParams(request.path)
        request.headers = try readHeaders(socket)
        if let contentLength = request.headers["content-length"], let contentLengthValue = Int(contentLength) {
            request.body = try readBody(socket, size: contentLengthValue)
        }
        return request
    }
    
    private func extractQueryParams(_ url: String) -> [(String, String)] {
        guard let query = url.split("?").last else {
            return []
        }
        return query.split("&").reduce([(String, String)]()) { (c, s) -> [(String, String)] in
            let tokens = s.split(1, separator: "=")
            if let name = tokens.first, let value = tokens.last {
                return c + [(name.removePercentEncoding(), value.removePercentEncoding())]
            }
            return c
        }
    }
    
    private func readBody(_ socket: Socket, size: Int) throws -> [UInt8] {
        var body = [UInt8]()
        for _ in 0..<size { body.append(try socket.read()) }
        return body
    }
    
    private func readHeaders(_ socket: Socket) throws -> [String: String] {
        var headers = [String: String]()
        while case let headerLine = try socket.readLine() , !headerLine.isEmpty {
            let headerTokens = headerLine.split(1, separator: ":")
            if let name = headerTokens.first, let value = headerTokens.last {
                headers[name.lowercased()] = value.trim()
            }
        }
        return headers
    }
    
    func supportsKeepAlive(_ headers: [String: String]) -> Bool {
        if let value = headers["connection"] {
            return "keep-alive" == value.trim()
        }
        return false
    }
}