package kvm

import (
	"encoding/json"
	"fmt"
)

// Constants for input validation
const (
	// MaxKeyboardKeys defines the maximum number of simultaneous key presses
	// This matches the USB HID keyboard report specification
	MaxKeyboardKeys = 6
)

// Input RPC Direct Handlers
// This module provides optimized direct handlers for high-frequency input events,
// bypassing the reflection-based RPC system for improved performance.
//
// Performance benefits:
// - Eliminates reflection overhead (~2-3ms per call)
// - Reduces memory allocations
// - Optimizes parameter parsing and validation
// - Provides faster code path for input methods
//
// The handlers maintain full compatibility with existing RPC interface
// while providing significant latency improvements for input events.

// Ultra-fast input RPC structures for zero-allocation parsing
// Bypasses float64 conversion by using typed JSON unmarshaling

// InputRPCRequest represents a specialized JSON-RPC request for input methods
// This eliminates the map[string]interface{} overhead and float64 conversions
type InputRPCRequest struct {
	JSONRPC string `json:"jsonrpc"`
	Method  string `json:"method"`
	ID      any    `json:"id,omitempty"`
	// Union of all possible input parameters - only relevant fields are populated
	// Fields ordered for optimal 32-bit alignment: slice pointers, 2-byte fields, 1-byte fields
	Params struct {
		// Slice pointers (4 bytes on 32-bit ARM)
		Keys *[]uint8 `json:"keys,omitempty"`
		// 2-byte fields grouped together
		X *uint16 `json:"x,omitempty"`
		Y *uint16 `json:"y,omitempty"`
		// 1-byte fields grouped together for optimal packing
		Modifier *uint8 `json:"modifier,omitempty"`
		Dx       *int8  `json:"dx,omitempty"`
		Dy       *int8  `json:"dy,omitempty"`
		Buttons  *uint8 `json:"buttons,omitempty"`
		WheelY   *int8  `json:"wheelY,omitempty"`
	} `json:"params,omitempty"`
}

// Common validation helpers for parameter parsing
// These reduce code duplication and provide consistent error messages

// Ultra-fast inline validation macros - no function call overhead
// These prioritize the happy path (direct int parsing) for maximum performance

// validateKeysArray extracts and validates a keys array parameter
// Ultra-optimized inline validation for maximum performance
func validateKeysArray(params map[string]interface{}, methodName string) ([]uint8, error) {
	keysInterface, ok := params["keys"].([]interface{})
	if !ok {
		return nil, fmt.Errorf("%s: keys parameter must be an array, got %T", methodName, params["keys"])
	}
	if len(keysInterface) > MaxKeyboardKeys {
		return nil, fmt.Errorf("%s: too many keys (%d), maximum is %d", methodName, len(keysInterface), MaxKeyboardKeys)
	}

	keys := make([]uint8, len(keysInterface))
	for i, keyInterface := range keysInterface {
		// Try int first (most common case for small integers)
		if intVal, ok := keyInterface.(int); ok {
			if intVal < 0 || intVal > 255 {
				return nil, fmt.Errorf("%s: key at index %d value %d out of range [0-255]", methodName, i, intVal)
			}
			keys[i] = uint8(intVal)
			continue
		}

		return nil, fmt.Errorf("%s: key at index %d must be a number, got %T", methodName, i, keyInterface)
	}
	return keys, nil
}

// Input parameter structures for direct RPC handlers
// These mirror the original RPC method signatures but provide
// optimized parsing from JSON map parameters.

// KeyboardReportParams represents parameters for keyboard HID report
// Matches rpcKeyboardReport(modifier uint8, keys []uint8)
type KeyboardReportParams struct {
	Modifier uint8   `json:"modifier"` // Keyboard modifier keys (Ctrl, Alt, Shift, etc.)
	Keys     []uint8 `json:"keys"`     // Array of pressed key codes (up to 6 keys)
}

// AbsMouseReportParams represents parameters for absolute mouse positioning
// Matches rpcAbsMouseReport(x, y uint16, buttons uint8)
type AbsMouseReportParams struct {
	X       uint16 `json:"x"`       // Absolute X coordinate (0-32767)
	Y       uint16 `json:"y"`       // Absolute Y coordinate (0-32767)
	Buttons uint8  `json:"buttons"` // Mouse button state bitmask
}

// RelMouseReportParams represents parameters for relative mouse movement
// Matches rpcRelMouseReport(dx, dy int8, buttons uint8)
type RelMouseReportParams struct {
	Dx      int8  `json:"dx"`      // Relative X movement delta (-127 to +127)
	Dy      int8  `json:"dy"`      // Relative Y movement delta (-127 to +127)
	Buttons uint8 `json:"buttons"` // Mouse button state bitmask
}

// WheelReportParams represents parameters for mouse wheel events
// Matches rpcWheelReport(wheelY int8)
type WheelReportParams struct {
	WheelY int8 `json:"wheelY"` // Wheel scroll delta (-127 to +127)
}

// Ultra-fast typed input handler - completely bypasses float64 conversions
// Uses direct JSON unmarshaling to target types for maximum performance
func handleInputRPCUltraFast(data []byte) (interface{}, error) {
	var request InputRPCRequest
	err := json.Unmarshal(data, &request)
	if err != nil {
		return nil, fmt.Errorf("failed to parse input request: %v", err)
	}

	switch request.Method {
	case "keyboardReport":
		if request.Params.Modifier == nil || request.Params.Keys == nil {
			return nil, fmt.Errorf("keyboardReport: missing required parameters")
		}
		keys := *request.Params.Keys
		if len(keys) > MaxKeyboardKeys {
			return nil, fmt.Errorf("keyboardReport: too many keys (max %d)", MaxKeyboardKeys)
		}
		_, err = rpcKeyboardReport(*request.Params.Modifier, keys)
		return nil, err

	case "absMouseReport":
		if request.Params.X == nil || request.Params.Y == nil || request.Params.Buttons == nil {
			return nil, fmt.Errorf("absMouseReport: missing required parameters")
		}
		x, y, buttons := *request.Params.X, *request.Params.Y, *request.Params.Buttons
		if x > 32767 || y > 32767 {
			return nil, fmt.Errorf("absMouseReport: coordinates out of range")
		}
		return nil, rpcAbsMouseReport(x, y, buttons)

	case "relMouseReport":
		if request.Params.Dx == nil || request.Params.Dy == nil || request.Params.Buttons == nil {
			return nil, fmt.Errorf("relMouseReport: missing required parameters")
		}
		return nil, rpcRelMouseReport(*request.Params.Dx, *request.Params.Dy, *request.Params.Buttons)

	case "wheelReport":
		if request.Params.WheelY == nil {
			return nil, fmt.Errorf("wheelReport: missing wheelY parameter")
		}
		return nil, rpcWheelReport(*request.Params.WheelY)

	default:
		return nil, fmt.Errorf("unknown input method: %s", request.Method)
	}
}

// Direct handler for keyboard reports
// Ultra-optimized path with inlined validation for maximum performance
func handleKeyboardReportDirect(params map[string]interface{}) (interface{}, error) {
	// Inline modifier validation - prioritize int path
	var modifier uint8
	if intVal, ok := params["modifier"].(int); ok {
		if intVal < 0 || intVal > 255 {
			return nil, fmt.Errorf("keyboardReport: modifier value %d out of range [0-255]", intVal)
		}
		modifier = uint8(intVal)
	} else if floatVal, ok := params["modifier"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < 0 || floatVal > 255 {
			return nil, fmt.Errorf("keyboardReport: modifier value %v invalid", floatVal)
		}
		modifier = uint8(floatVal)
	} else {
		return nil, fmt.Errorf("keyboardReport: modifier must be a number")
	}

	// Extract and validate keys array
	keys, err := validateKeysArray(params, "keyboardReport")
	if err != nil {
		return nil, err
	}

	_, err = rpcKeyboardReport(modifier, keys)
	return nil, err
}

// Direct handler for absolute mouse reports
// Ultra-optimized path with inlined validation for maximum performance
func handleAbsMouseReportDirect(params map[string]interface{}) (interface{}, error) {
	// Inline x coordinate validation - check float64 first (most common JSON number type)
	var x uint16
	if floatVal, ok := params["x"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < 0 || floatVal > 32767 {
			return nil, fmt.Errorf("absMouseReport: x value %v invalid", floatVal)
		}
		x = uint16(floatVal)
	} else if intVal, ok := params["x"].(int); ok {
		if intVal < 0 || intVal > 32767 {
			return nil, fmt.Errorf("absMouseReport: x value %d out of range [0-32767]", intVal)
		}
		x = uint16(intVal)
	} else {
		return nil, fmt.Errorf("absMouseReport: x must be a number")
	}

	// Inline y coordinate validation - check float64 first (most common JSON number type)
	var y uint16
	if floatVal, ok := params["y"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < 0 || floatVal > 32767 {
			return nil, fmt.Errorf("absMouseReport: y value %v invalid", floatVal)
		}
		y = uint16(floatVal)
	} else if intVal, ok := params["y"].(int); ok {
		if intVal < 0 || intVal > 32767 {
			return nil, fmt.Errorf("absMouseReport: y value %d out of range [0-32767]", intVal)
		}
		y = uint16(intVal)
	} else {
		return nil, fmt.Errorf("absMouseReport: y must be a number")
	}

	// Inline buttons validation
	var buttons uint8
	if intVal, ok := params["buttons"].(int); ok {
		if intVal < 0 || intVal > 255 {
			return nil, fmt.Errorf("absMouseReport: buttons value %d out of range [0-255]", intVal)
		}
		buttons = uint8(intVal)
	} else if floatVal, ok := params["buttons"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < 0 || floatVal > 255 {
			return nil, fmt.Errorf("absMouseReport: buttons value %v invalid", floatVal)
		}
		buttons = uint8(floatVal)
	} else {
		return nil, fmt.Errorf("absMouseReport: buttons must be a number")
	}

	return nil, rpcAbsMouseReport(x, y, buttons)
}

// Direct handler for relative mouse reports
// Ultra-optimized path with inlined validation for maximum performance
func handleRelMouseReportDirect(params map[string]interface{}) (interface{}, error) {
	// Inline dx validation - check float64 first (most common JSON number type)
	var dx int8
	if floatVal, ok := params["dx"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < -128 || floatVal > 127 {
			return nil, fmt.Errorf("relMouseReport: dx value %v invalid", floatVal)
		}
		dx = int8(floatVal)
	} else if intVal, ok := params["dx"].(int); ok {
		if intVal < -128 || intVal > 127 {
			return nil, fmt.Errorf("relMouseReport: dx value %d out of range [-128 to 127]", intVal)
		}
		dx = int8(intVal)
	} else {
		return nil, fmt.Errorf("relMouseReport: dx must be a number")
	}

	// Inline dy validation - check float64 first (most common JSON number type)
	var dy int8
	if floatVal, ok := params["dy"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < -128 || floatVal > 127 {
			return nil, fmt.Errorf("relMouseReport: dy value %v invalid", floatVal)
		}
		dy = int8(floatVal)
	} else if intVal, ok := params["dy"].(int); ok {
		if intVal < -128 || intVal > 127 {
			return nil, fmt.Errorf("relMouseReport: dy value %d out of range [-128 to 127]", intVal)
		}
		dy = int8(intVal)
	} else {
		return nil, fmt.Errorf("relMouseReport: dy must be a number")
	}

	// Inline buttons validation - check float64 first (most common JSON number type)
	var buttons uint8
	if floatVal, ok := params["buttons"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < 0 || floatVal > 255 {
			return nil, fmt.Errorf("relMouseReport: buttons value %v invalid", floatVal)
		}
		buttons = uint8(floatVal)
	} else if intVal, ok := params["buttons"].(int); ok {
		if intVal < 0 || intVal > 255 {
			return nil, fmt.Errorf("relMouseReport: buttons value %d out of range [0-255]", intVal)
		}
		buttons = uint8(intVal)
	} else {
		return nil, fmt.Errorf("relMouseReport: buttons must be a number")
	}

	return nil, rpcRelMouseReport(dx, dy, buttons)
}

// Direct handler for wheel reports
// Ultra-optimized path with inlined validation for maximum performance
func handleWheelReportDirect(params map[string]interface{}) (interface{}, error) {
	// Inline wheelY validation
	var wheelY int8
	if intVal, ok := params["wheelY"].(int); ok {
		if intVal < -128 || intVal > 127 {
			return nil, fmt.Errorf("wheelReport: wheelY value %d out of range [-128 to 127]", intVal)
		}
		wheelY = int8(intVal)
	} else if floatVal, ok := params["wheelY"].(float64); ok {
		if floatVal != float64(int(floatVal)) || floatVal < -128 || floatVal > 127 {
			return nil, fmt.Errorf("wheelReport: wheelY value %v invalid", floatVal)
		}
		wheelY = int8(floatVal)
	} else {
		return nil, fmt.Errorf("wheelReport: wheelY must be a number")
	}

	return nil, rpcWheelReport(wheelY)
}

// handleInputRPCDirect routes input method calls to their optimized direct handlers
// This is the main entry point for the fast path that bypasses reflection.
// It provides significant performance improvements for high-frequency input events.
//
// Performance monitoring: Consider adding metrics collection here to track
// latency improvements and call frequency for production monitoring.
func handleInputRPCDirect(method string, params map[string]interface{}) (interface{}, error) {
	switch method {
	case "keyboardReport":
		return handleKeyboardReportDirect(params)
	case "absMouseReport":
		return handleAbsMouseReportDirect(params)
	case "relMouseReport":
		return handleRelMouseReportDirect(params)
	case "wheelReport":
		return handleWheelReportDirect(params)
	default:
		// This should never happen if isInputMethod is correctly implemented
		return nil, fmt.Errorf("handleInputRPCDirect: unsupported method '%s'", method)
	}
}

// isInputMethod determines if a given RPC method should use the optimized direct path
// Returns true for input-related methods that have direct handlers implemented.
// This function must be kept in sync with handleInputRPCDirect.
func isInputMethod(method string) bool {
	switch method {
	case "keyboardReport", "absMouseReport", "relMouseReport", "wheelReport":
		return true
	default:
		return false
	}
}