package calculator

import (
	"context"
	"fmt"
	"math"
	"strconv"
	"strings"
	"unicode"

	"git.yeij.top/AskaEth/Cyrene-Plugins/sdk"
)

type CalculatorPlugin struct {
	sdk.BasePlugin
}

func (p *CalculatorPlugin) Metadata() sdk.PluginMetadata {
	return sdk.PluginMetadata{
		Name: "calculator", DisplayName: "Calculator", Version: "1.0.0",
		Description: "Safe mathematical expression evaluation with custom parser",
		Category: "utility", Author: sdk.PluginAuthor{Name: "Cyrene Team"},
	}
}

func (p *CalculatorPlugin) Tools() []sdk.Tool {
	return []sdk.Tool{&CalculatorTool{}}
}

type CalculatorTool struct {
	sdk.BaseTool
}

func (t *CalculatorTool) Definition() sdk.ToolDefinition {
	return sdk.ToolDefinition{
		ID: "calculator", Name: "calculator", DisplayName: "Calculator",
		Description: "Execute mathematical calculations. Supports arithmetic, trig, logs, powers.",
		Category: "utility", Complexity: sdk.ComplexitySimple,
		Parameters: map[string]interface{}{
			"type": "object", "properties": map[string]interface{}{"expression": map[string]interface{}{"type": "string"}},
			"required": []string{"expression"},
		},
	}
}

func (t *CalculatorTool) Validate(args map[string]interface{}) error {
	if _, ok := args["expression"]; !ok {
		return fmt.Errorf("missing required parameter: expression")
	}
	return nil
}

func (t *CalculatorTool) Execute(_ context.Context, args map[string]interface{}) (*sdk.ToolResult, error) {
	expr, _ := args["expression"].(string)
	result, err := evalExpression(expr)
	if err != nil {
		return &sdk.ToolResult{ToolName: "calculator", Success: false, Error: err.Error()}, nil
	}
	return &sdk.ToolResult{ToolName: "calculator", Success: true, Output: fmt.Sprintf("%v", result)}, nil
}

// Expression parser supporting +, -, *, /, %, ^, functions, constants.
type exprParser struct {
	s   string
	pos int
}

func evalExpression(s string) (float64, error) {
	p := &exprParser{s: strings.TrimSpace(s)}
	result, err := p.parseAddSub()
	if err != nil {
		return 0, err
	}
	if p.pos < len(p.s) {
		return 0, fmt.Errorf("unexpected character at position %d: %c", p.pos, p.s[p.pos])
	}
	return result, nil
}

func (p *exprParser) peek() byte {
	if p.pos < len(p.s) {
		return p.s[p.pos]
	}
	return 0
}

func (p *exprParser) skipSpaces() {
	for p.pos < len(p.s) && p.s[p.pos] == ' ' {
		p.pos++
	}
}

func (p *exprParser) parseAddSub() (float64, error) {
	left, err := p.parseMulDiv()
	if err != nil {
		return 0, err
	}
	for {
		p.skipSpaces()
		op := p.peek()
		if op != '+' && op != '-' {
			break
		}
		p.pos++
		right, err := p.parseMulDiv()
		if err != nil {
			return 0, err
		}
		if op == '+' {
			left += right
		} else {
			left -= right
		}
	}
	return left, nil
}

func (p *exprParser) parseMulDiv() (float64, error) {
	left, err := p.parsePower()
	if err != nil {
		return 0, err
	}
	for {
		p.skipSpaces()
		op := p.peek()
		if op != '*' && op != '/' && op != '%' {
			break
		}
		p.pos++
		right, err := p.parsePower()
		if err != nil {
			return 0, err
		}
		switch op {
		case '*':
			left *= right
		case '/':
			if right == 0 {
				return 0, fmt.Errorf("division by zero")
			}
			left /= right
		case '%':
			left = math.Mod(left, right)
		}
	}
	return left, nil
}

func (p *exprParser) parsePower() (float64, error) {
	left, err := p.parseUnary()
	if err != nil {
		return 0, err
	}
	p.skipSpaces()
	if p.peek() == '^' {
		p.pos++
		right, err := p.parseUnary()
		if err != nil {
			return 0, err
		}
		return math.Pow(left, right), nil
	}
	return left, nil
}

func (p *exprParser) parseUnary() (float64, error) {
	p.skipSpaces()
	if p.peek() == '-' {
		p.pos++
		val, err := p.parseAtom()
		if err != nil {
			return 0, err
		}
		return -val, nil
	}
	if p.peek() == '+' {
		p.pos++
	}
	return p.parseAtom()
}

func (p *exprParser) parseAtom() (float64, error) {
	p.skipSpaces()
	if p.peek() == '(' {
		p.pos++
		result, err := p.parseAddSub()
		if err != nil {
			return 0, err
		}
		p.skipSpaces()
		if p.peek() != ')' {
			return 0, fmt.Errorf("missing closing parenthesis")
		}
		p.pos++
		return result, nil
	}
	if p.peek() == 0 {
		return 0, fmt.Errorf("unexpected end of expression")
	}
	if unicode.IsDigit(rune(p.peek())) || p.peek() == '.' {
		return p.parseNumber()
	}
	return p.parseFuncOrConst()
}

func (p *exprParser) parseNumber() (float64, error) {
	start := p.pos
	for p.pos < len(p.s) && (unicode.IsDigit(rune(p.s[p.pos])) || p.s[p.pos] == '.') {
		p.pos++
	}
	return strconv.ParseFloat(p.s[start:p.pos], 64)
}

func (p *exprParser) parseFuncOrConst() (float64, error) {
	start := p.pos
	for p.pos < len(p.s) && (unicode.IsLetter(rune(p.s[p.pos])) || p.s[p.pos] == '_') {
		p.pos++
	}
	name := p.s[start:p.pos]
	p.skipSpaces()

	switch name {
	case "pi":
		return math.Pi, nil
	case "e":
		return math.E, nil
	case "sqrt", "sin", "cos", "tan", "abs", "floor", "ceil", "round", "log", "ln":
		if p.peek() != '(' {
			return 0, fmt.Errorf("expected '(' after function %s", name)
		}
		p.pos++
		arg, err := p.parseAddSub()
		if err != nil {
			return 0, err
		}
		if p.peek() != ')' {
			return 0, fmt.Errorf("missing ')' after function argument")
		}
		p.pos++
		return applyFunc(name, arg)
	default:
		return 0, fmt.Errorf("unknown function or constant: %s", name)
	}
}

func applyFunc(name string, x float64) (float64, error) {
	switch name {
	case "sqrt":
		if x < 0 {
			return 0, fmt.Errorf("square root of negative number")
		}
		return math.Sqrt(x), nil
	case "sin":
		return math.Sin(x), nil
	case "cos":
		return math.Cos(x), nil
	case "tan":
		return math.Tan(x), nil
	case "abs":
		return math.Abs(x), nil
	case "floor":
		return math.Floor(x), nil
	case "ceil":
		return math.Ceil(x), nil
	case "round":
		return math.Round(x), nil
	case "log":
		if x <= 0 {
			return 0, fmt.Errorf("log of non-positive number")
		}
		return math.Log10(x), nil
	case "ln":
		if x <= 0 {
			return 0, fmt.Errorf("ln of non-positive number")
		}
		return math.Log(x), nil
	}
	return 0, fmt.Errorf("unknown function: %s", name)
}