//
// Copyright 2026 Aarav Ravindra Kharade
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
import CSystem
public struct ArkInputEvent {
    public var type: UInt8
    public var padding: UInt8
    public var code: UInt16
    public var value: Int32
}

public class ArkInput {
    private var fd: Int32 = -1
    public private(set) var isConnected: Bool = false
    
    // Mouse state
    public var mouseX: Int = 512
    public var mouseY: Int = 384
    public var leftMouseDown: Bool = false
    public var rightMouseDown: Bool = false
    public var leftShiftDown: Bool = false
    public var rightShiftDown: Bool = false
    
    // Key codes
    private static let keyMap: [UInt16: Character] = [
        2: "1", 3: "2", 4: "3", 5: "4", 6: "5", 7: "6", 8: "7", 9: "8", 10: "9", 11: "0",
        12: "-", 13: "=",
        16: "q", 17: "w", 18: "e", 19: "r", 20: "t", 21: "y", 22: "u", 23: "i", 24: "o", 25: "p",
        26: "[", 27: "]", 28: "\n",
        30: "a", 31: "s", 32: "d", 33: "f", 34: "g", 35: "h", 36: "j", 37: "k", 38: "l",
        39: ";", 40: "'", 41: "`", 43: "\\",
        44: "z", 45: "x", 46: "c", 47: "v", 48: "b", 49: "n", 50: "m",
        51: ",", 52: ".", 53: "/",
        57: " ", // Space
        14: "\u{08}" // Backspace
    ]

    private static let shiftKeyMap: [UInt16: Character] = [
        2: "!", 3: "@", 4: "#", 5: "$", 6: "%", 7: "^", 8: "&", 9: "*", 10: "(", 11: ")",
        12: "_", 13: "+",
        16: "Q", 17: "W", 18: "E", 19: "R", 20: "T", 21: "Y", 22: "U", 23: "I", 24: "O", 25: "P",
        26: "{", 27: "}", 28: "\n",
        30: "A", 31: "S", 32: "D", 33: "F", 34: "G", 35: "H", 36: "J", 37: "K", 38: "L",
        39: ":", 40: "\"", 41: "~", 43: "|",
        44: "Z", 45: "X", 46: "C", 47: "V", 48: "B", 49: "N", 50: "M",
        51: "<", 52: ">", 53: "?",
        57: " ",
        14: "\u{08}"
    ]
    
    public init() {
        #if canImport(Glibc)
        fd = socket(AF_UNIX, Int32(SOCK_STREAM.rawValue), 0)
        #else
        fd = socket(AF_UNIX, Int32(SOCK_STREAM), 0)
        #endif
        if fd < 0 { return }
        
        var addr = sockaddr_un()
        addr.sun_family = sa_family_t(AF_UNIX)
        let socketPath = "/dev/input.sock"
        let pathBytes = socketPath.utf8CString
        withUnsafeMutablePointer(to: &addr.sun_path) { sunPathPtr in
            let rawPtr = UnsafeMutableRawPointer(sunPathPtr).assumingMemoryBound(to: CChar.self)
            for i in 0..<min(pathBytes.count, 108) {
                rawPtr[i] = pathBytes[i]
            }
        }
        
        var retries = 50
        while retries > 0 {
            let result = withUnsafePointer(to: &addr) { addrPtr in
                addrPtr.withMemoryRebound(to: sockaddr.self, capacity: 1) { saPtr in
                    connect(fd, saPtr, socklen_t(MemoryLayout<sockaddr_un>.size))
                }
            }
            if result == 0 {
                isConnected = true
                
                // Use MSG_DONTWAIT in recv() instead of setting socket to non-blocking
                // to avoid variadic fcntl() linking issues in Swift Musl.
                return
            }
            usleep(100_000)
            retries -= 1
        }
        close(fd)
    }
    
    public func pollEvents(scrW: Int, scrH: Int) -> [ArkInputEvent] {
        guard isConnected else { return [] }
        var events = [ArkInputEvent]()
        
        let evSize = 8
        let buf = UnsafeMutablePointer<UInt8>.allocate(capacity: evSize)
        defer { buf.deallocate() }
        
        while true {
            let bytesRead = recv(fd, buf, evSize, Int32(MSG_DONTWAIT))
            if bytesRead <= 0 {
                break // EAGAIN or closed
            }
            
            var totalRead = bytesRead
            while totalRead < evSize {
                let more = read(fd, buf + totalRead, evSize - totalRead)
                if more <= 0 { break }
                totalRead += more
            }
            
            if totalRead == evSize {
                let type = buf[0]
                var code: UInt16 = 0
                var value: Int32 = 0
                memcpy(&code, buf + 2, 2)
                memcpy(&value, buf + 4, 4)
                
                let event = ArkInputEvent(type: type, padding: 0, code: code, value: value)
                events.append(event)
                
                // Update internal state
                if type == 1 { // EV_KEY
                    if code == 0x110 { // BTN_LEFT
                        leftMouseDown = (value != 0)
                    } else if code == 0x111 { // BTN_RIGHT
                        rightMouseDown = (value != 0)
                    } else if code == 42 { // KEY_LEFTSHIFT
                        leftShiftDown = (value != 0)
                    } else if code == 54 { // KEY_RIGHTSHIFT
                        rightShiftDown = (value != 0)
                    }
                } else if type == 2 { // EV_REL
                    if code == 0 { // REL_X
                        mouseX = max(0, min(scrW - 1, mouseX + Int(value)))
                    } else if code == 1 { // REL_Y
                        mouseY = max(0, min(scrH - 1, mouseY - Int(value)))
                    }
                } else if type == 3 { // EV_ABS
                    if code == 0 { // ABS_X
                        let scaledX = (Int(value) * scrW) / 32768
                        mouseX = max(0, min(scrW - 1, scaledX))
                    } else if code == 1 { // ABS_Y
                        let scaledY = (Int(value) * scrH) / 32768
                        mouseY = max(0, min(scrH - 1, (scrH - 1) - scaledY))
                    }
                }
            } else {
                break // Stream broken
            }
        }
        return events
    }
    
    public func mapKey(code: UInt16) -> Character? {
        let isShiftDown = leftShiftDown || rightShiftDown
        if isShiftDown {
            return ArkInput.shiftKeyMap[code]
        } else {
            return ArkInput.keyMap[code]
        }
    }
}