package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"github.com/chzyer/readline"
)

var assignmentRegex = regexp.MustCompile(`^([a-zA-Z_][a-zA-Z0-9_]*)\s*=\s*(.*)$`)
var funcAssignmentRegex = regexp.MustCompile(`^([a-zA-Z_][a-zA-Z0-9_]*)\s*\(([^)]*)\)\s*=\s*(.*)$`)

func isReservedName(name string) bool {
	upper := strings.ToUpper(name)
	if upper == "PI" || upper == "E" { return true }
	lower := strings.ToLower(name)
	switch lower {
	case "help", "units", "rates", "base", "clear", "exit", "quit", "var", "cur", "unset", "funcs", "ans", "_":
		return true
	}
	switch lower {
	case "sin", "cos", "tan", "asin", "acos", "atan", "sinh", "cosh", "tanh",
		"sqrt", "log", "log2", "ln", "exp", "abs", "ceil", "floor", "round", "pow", "min", "max", "mod", "fact", "if",
		"ip", "cidr", "network", "broadcast", "mask", "hosts", "range":
		return true
	}
	if _, ok := unitRegistry[upper]; ok { return true }
	return false
}

func loadVariables(path string) error {
	file, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("could not open variables file: %w", err)
	}
	defer file.Close()

	decoder := json.NewDecoder(file)
	if err := decoder.Decode(&variables); err != nil {
		return fmt.Errorf("could not decode variables json: %w", err)
	}
	return nil
}

func saveVariables(path string) error {
	file, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("could not create variables file: %w", err)
	}
	defer file.Close()

	encoder := json.NewEncoder(file)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(variables); err != nil {
		return fmt.Errorf("could not encode variables json: %w", err)
	}
	return nil
}

func loadUserFuncs(path string) error {
	file, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("could not open functions file: %w", err)
	}
	defer file.Close()

	decoder := json.NewDecoder(file)
	if err := decoder.Decode(&userFuncs); err != nil {
		return fmt.Errorf("could not decode functions json: %w", err)
	}
	return nil
}

func saveUserFuncs(path string) error {
	file, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("could not create functions file: %w", err)
	}
	defer file.Close()

	encoder := json.NewEncoder(file)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(userFuncs); err != nil {
		return fmt.Errorf("could not encode functions json: %w", err)
	}
	return nil
}


func printHelp() {
	fmt.Println("\033[1;34mgoca Help\033[0m")
	fmt.Println("\033[1mArithmetic & Operators:\033[0m")
	fmt.Println("  Basic:     +, -, *, /, % (modulo)")
	fmt.Println("  Power:     a ** b  or  pow(a, b)")
	fmt.Println("  Bitwise:   & (AND), | (OR), ^ (XOR), ~ (NOT), << (Left Shift), >> (Right Shift)")
	fmt.Println("  Logic:     ==, !=, <, >, <=, >=, ! (NOT)")
	fmt.Println("  Implicit:  2(3 + 4) or 2m (implicit multiplication)")
	fmt.Println("  Numbers:   Decimal (10), Hex (0xFF), Binary (0b1010), Octal (0o77)")
	fmt.Println("  Variables: Assign (e.g. x = 5), Use 'ans' or '_' for last result")
	fmt.Println("  Custom Fn: f(x, y) = x * y + 2")
	fmt.Println("\033[1mScientific Functions:\033[0m")
	fmt.Println("  Trig:      sin(x), cos(x), tan(x) (accepts angles like 90 deg or pi rad)")
	fmt.Println("  Inv Trig:  asin(x), acos(x), atan(x) (returns angles, e.g., asin(1) to deg)")
	fmt.Println("  Hyper:     sinh(x), cosh(x), tanh(x)")
	fmt.Println("  General:   sqrt(x), abs(x), exp(x), ln(x) (natural), log(x) (base 10), log2(x)")
	fmt.Println("  Rounding:  ceil(x), floor(x), round(x)")
	fmt.Println("  Stats:     min(a, b, ...), max(a, b, ...), mod(a, b), fact(x) (factorial)")
	fmt.Println("  Logic:     if(cond, true_val, false_val)")
	fmt.Println("  Constants: PI, E")
	fmt.Println("\033[1mIP & Subnet:\033[0m")
	fmt.Println("  Parse:     ip(\"192.168.1.1\"), cidr(\"10.0.0.0/24\")")
	fmt.Println("  Subnet:    network(c), broadcast(c), mask(c), hosts(c), range(c)")
	fmt.Println("\033[1mUnits & Conversions:\033[0m")
	fmt.Println("  Syntax:    <value> <unit> to/in <unit> (e.g., 10 mi to km, 1 GB in MB)")
	fmt.Println("  Types:     Length, Mass, Time, Digital, Area, Temperature, Angle")
	fmt.Println("  Example:   0 C to K, 90 deg to rad, 32 F to C")
	fmt.Println("\033[1mCurrencies (Live Rates):\033[0m")
	fmt.Println("  Usage:     Exchange currency codes (e.g., 100 USD to EUR)")
	fmt.Println("  Symbols:   $, €, £, ¥ (e.g., 10$ to €)")
	fmt.Println("\033[1mCommands:\033[0m")
	fmt.Println("  help       Show this help information")
	fmt.Println("  units      List all supported measurement units")
	fmt.Println("  rates      Show common currency exchange rates relative to base")
	fmt.Println("  cur        List all supported live currency codes")
	fmt.Println("  var        List all user-defined variables")
	fmt.Println("  funcs      List all user-defined functions")
	fmt.Println("  unset <v>  Delete variable <v> (or 'unset *' to delete all)")
	fmt.Println("  base <C>   Change base currency (e.g., base USD)")
	fmt.Println("  clear      Clear the terminal screen")
	fmt.Println("  exit/quit  Exit goca")
}

type CalcCompleter struct{}

func (c *CalcCompleter) Do(line []rune, pos int) (newLine [][]rune, length int) {
	var wordStart = pos
	for wordStart > 0 {
		ch := line[wordStart-1]
		if (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || ch == '_' {
			wordStart--
		} else {
			break
		}
	}
	word := string(line[wordStart:pos])
	if word == "" {
		return nil, 0
	}

	allCandidates := []string{
		"help", "units", "rates", "cur", "var", "funcs", "clear", "exit", "quit", "base", "unset",
		"sin", "cos", "tan", "asin", "acos", "atan", "sinh", "cosh", "tanh",
		"sqrt", "log", "log2", "ln", "exp", "abs", "ceil", "floor", "round", "pow", "min", "max", "mod", "fact", "if",
		"ip", "cidr", "network", "broadcast", "mask", "hosts", "range",
		"PI", "E", "ans", "_",
	}
	for u := range unitRegistry {
		allCandidates = append(allCandidates, strings.ToLower(u))
		allCandidates = append(allCandidates, u)
	}

	var matches []string
	seen := make(map[string]bool)
	for _, cand := range allCandidates {
		if strings.HasPrefix(strings.ToLower(cand), strings.ToLower(word)) {
			if !seen[cand] {
				seen[cand] = true
				matches = append(matches, cand)
			}
		}
	}
	for v := range variables {
		if strings.HasPrefix(strings.ToLower(v), strings.ToLower(word)) {
			if !seen[v] {
				seen[v] = true
				matches = append(matches, v)
			}
	for uf := range userFuncs {
		if strings.HasPrefix(strings.ToLower(uf), strings.ToLower(word)) {
			if !seen[uf] {
				seen[uf] = true
				matches = append(matches, uf)
			}
		}
	}
		}
	}

	sort.Strings(matches)

	var ret [][]rune
	for _, m := range matches {
		suffix := m[len(word):]
		isFunc := false
		switch m {
		case "sin", "cos", "tan", "asin", "acos", "atan", "sinh", "cosh", "tanh",
			"sqrt", "log", "log2", "ln", "exp", "abs", "ceil", "floor", "round", "pow", "min", "max", "mod", "fact", "if",
			"ip", "cidr", "network", "broadcast", "mask", "hosts", "range":
			isFunc = true
		}
		if isFunc || func() bool { _, ok := userFuncs[m]; return ok }() {
			suffix += "("
		}
		ret = append(ret, []rune(suffix))
	}

	return ret, len(word)
}

func printResult(res Result, target string) {
	if res.Dim == DimString {
		fmt.Printf("\033[1;33m= \"%s\"\033[0m\n", stringTable[res.Value.IntPart()])
		return
	}
	
	val := res.Value
	if target != "" {
		fmt.Printf("\033[1;33m= %v %s\033[0m\n", val, target)
	} else if res.Dim == DimCurrency {
		rateToBase := d(1.0).Div(eurRatesLookup(baseCurrency))
		result := val.Mul(rateToBase)

		if result.IsInteger() {
			i := result.IntPart()
			fmt.Printf("\033[1;33m%d %s\033[0m", i, baseCurrency)
			if baseCurrency == "EUR" || baseCurrency == "USD" {
				fmt.Printf(" (Hex: 0x%X, Bin: 0b%b)", i, i)
			}
			fmt.Println()
		} else {
			f, _ := result.Float64()
			fmt.Printf("\033[1;33m= %.4f %s\033[0m\n", f, baseCurrency)
		}
	} else if res.Dim == DimIP {
		i := val.IntPart()
		fmt.Printf("\033[1;33m= %d.%d.%d.%d\033[0m\n", (i>>24)&0xFF, (i>>16)&0xFF, (i>>8)&0xFF, i&0xFF)
	} else if res.Dim == DimCIDR {
		i := val.IntPart()
		ipPart := i >> 8
		mask := i & 0xFF
		fmt.Printf("\033[1;33m= %d.%d.%d.%d/%d\033[0m\n", (ipPart>>24)&0xFF, (ipPart>>16)&0xFF, (ipPart>>8)&0xFF, ipPart&0xFF, mask)
	} else if res.Dim != DimNone {
		label := ""
		for _, v := range unitRegistry {
			if v.Dimension == res.Dim && v.Factor.Equal(d(1.0)) {
				label = v.Label
				break
			}
		}
		fmt.Printf("\033[1;33m= %v %s\033[0m\n", val, label)
	} else {
		if val.IsInteger() {
			i := val.IntPart()
			fmt.Printf("\033[1;33m%d\033[0m (0x%X, 0b%b)\n", i, i, i)
		} else {
			fmt.Printf("\033[1;33m= %v\033[0m\n", val)
		}
	}
}

func handleLine(line string, useReadline bool, variablesFile string, functionsFile string) bool {
	line = strings.TrimSpace(line)
	if line == "" {
		return false
	}
	
	lower := strings.ToLower(line)
	if lower == "exit" || lower == "quit" {
		return true
	}
	if lower == "clear" {
		if useReadline {
			fmt.Print("\033[2J\033[H")
		}
		return false
	}
	if lower == "help" {
		printHelp()
		return false
	}
	if lower == "units" {
		fmt.Println("Supported Units:")
		fmt.Println("  Length: km, m, dm, cm, mm, um, nm, mi, nmi, ft, in, yd")
		fmt.Println("  Mass: t, kg, g, mg, ct, lb, oz")
		fmt.Println("  Time: yr, wk, d, h, min, s, ms, us, ns")
		fmt.Println("  Digital: EB, PB, TB, GB, MB, KB, B")
		fmt.Println("  Area: km2, ha, acre, m2, cm2, mm2")
		fmt.Println("  Temperature: K, C, F")
		fmt.Println("  Angle: rad, deg, grad")
		return false
	}
	if lower == "rates" {
		fmt.Printf("Exchange rates (relative to %s):\n", baseCurrency)
		rateToBase := d(1.0).Div(eurRatesLookup(baseCurrency))
		for _, c := range []string{"EUR", "USD", "GBP", "JPY", "CHF", "CNY"} {
			if r, ok := unitRegistry[c]; ok {
				f, _ := r.Factor.Mul(rateToBase).Float64()
				fmt.Printf("  1 %s = %.4f %s\n", c, f, baseCurrency)
			}
		}
		return false
	}
	if lower == "cur" {
		var currencies []string
		for code, u := range unitRegistry {
			if u.Dimension == DimCurrency {
				currencies = append(currencies, code)
			}
		}
		sort.Strings(currencies)
		fmt.Println("Supported Currencies:")
		fmt.Println("  " + strings.Join(currencies, ", "))
		return false
	}
	if lower == "funcs" {
		if len(userFuncs) == 0 {
			fmt.Println("No user-defined functions.")
			return false
		}
		fmt.Println("Defined Functions:")
		var keys []string
		for k := range userFuncs {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, name := range keys {
			uf := userFuncs[name]
			fmt.Printf("  %s(%s) = %s\n", name, strings.Join(uf.Args, ", "), uf.Expr)
		}
		return false
	}

	if lower == "var" {
		if len(variables) == 0 {
			fmt.Println("No variables defined.")
			return false
		}
		fmt.Println("Defined Variables:")
		var keys []string
		for k := range variables {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, name := range keys {
			res := variables[name]
			if res.Dim == DimCurrency {
				fmt.Printf("  %s = %v (Currency)\n", name, res.Value)
			} else if res.Dim != DimNone {
				label := ""
				for _, v := range unitRegistry {
					if v.Dimension == res.Dim && v.Factor.Equal(d(1.0)) {
						label = v.Label
						break
					}
				}
				fmt.Printf("  %s = %v %s\n", name, res.Value, label)
			} else {
				fmt.Printf("  %s = %v\n", name, res.Value)
			}
		}
		return false
	}
	if strings.HasPrefix(lower, "base ") {
		newBase := strings.TrimSpace(line[5:])
		switch newBase {
		case "$":
			newBase = "USD"
		case "€":
			newBase = "EUR"
		case "£":
			newBase = "GBP"
		case "¥":
			newBase = "JPY"
		default:
			newBase = strings.ToUpper(newBase)
		}
		if _, ok := unitRegistry[newBase]; ok && unitRegistry[newBase].Dimension == DimCurrency {
			baseCurrency = newBase
			fmt.Printf("Base set to %s\n", baseCurrency)
		} else {
			fmt.Printf("Error: Unknown currency %s\n", newBase)
		}
		return false
	}
	if strings.HasPrefix(lower, "unset ") {
		target := strings.TrimSpace(line[6:])
		if target == "*" || strings.ToLower(target) == "all" {
			if len(variables) == 0 && len(userFuncs) == 0 {
				fmt.Println("No variables or functions defined.")
			} else {
				variables = make(map[string]Result)
				if err := saveVariables(variablesFile); err != nil {
					fmt.Printf("\033[1;31mWarning:\033[0m Failed to clear persisted variables: %v\n", err)
				}
				userFuncs = make(map[string]UserFunc)
				if err := saveUserFuncs(functionsFile); err != nil {
					fmt.Printf("\033[1;31mWarning:\033[0m Failed to clear persisted functions: %v\n", err)
				}
				fmt.Println("All variables and functions deleted.")
			}
		} else {
			found := false
			if _, ok := variables[target]; ok {
				delete(variables, target)
				if err := saveVariables(variablesFile); err != nil {
					fmt.Printf("\033[1;31mWarning:\033[0m Failed to persist variables: %v\n", err)
				}
				fmt.Printf("Variable '%s' deleted.\n", target)
				found = true
			}
			if _, ok := userFuncs[target]; ok {
				delete(userFuncs, target)
				if err := saveUserFuncs(functionsFile); err != nil {
					fmt.Printf("\033[1;31mWarning:\033[0m Failed to persist functions: %v\n", err)
				}
				fmt.Printf("Function '%s' deleted.\n", target)
				found = true
			}
			if !found {
				fmt.Printf("\033[1;31mError:\033[0m Variable or function '%s' not found.\n", target)
			}
		}
		return false
	}

	if matches := funcAssignmentRegex.FindStringSubmatch(line); matches != nil {
		name := matches[1]
		argsStr := matches[2]
		exprStr := matches[3]

		if isReservedName(name) {
			fmt.Printf("\033[1;31mError:\033[0m %s is a reserved name (constant, unit, function, or command)\n", name)
			return false
		}

		var args []string
		for _, a := range strings.Split(argsStr, ",") {
			a = strings.TrimSpace(a)
			if a != "" {
				args = append(args, a)
			}
		}

		p := NewParser(exprStr)
		_, err := p.Parse()
		if err != nil {
			fmt.Printf("\033[1;31mError:\033[0m Failed to parse function body: %v\n", err)
			return false
		}

		userFuncs[name] = UserFunc{Args: args, Expr: exprStr}
		if err := saveUserFuncs(functionsFile); err != nil {
			fmt.Printf("\033[1;31mWarning:\033[0m Failed to persist functions: %v\n", err)
		}
		fmt.Printf("\033[1;33mDefined function %s(%s)\033[0m\n", name, strings.Join(args, ", "))
		return false
	}

	if matches := assignmentRegex.FindStringSubmatch(line); matches != nil {
		name := matches[1]
		expr := matches[2]

		if isReservedName(name) {
			fmt.Printf("\033[1;31mError:\033[0m %s is a reserved name (constant, unit, function, or command)\n", name)
			return false
		}

		res, target, err := evaluate(expr)
		if err != nil {
			fmt.Printf("\033[1;31mError:\033[0m %v\n", err)
			return false
		}

		variables[name] = res
		variables["ans"] = res
		variables["_"] = res
		if err := saveVariables(variablesFile); err != nil {
			fmt.Printf("\033[1;31mWarning:\033[0m Failed to persist variables: %v\n", err)
		}

		if target != "" {
			fmt.Printf("\033[1;33m%s = %v %s\033[0m\n", name, res.Value, target)
		} else if res.Dim == DimCurrency {
			rateToBase := d(1.0).Div(eurRatesLookup(baseCurrency))
			result := res.Value.Mul(rateToBase)
			if result.IsInteger() {
				fmt.Printf("\033[1;33m%s = %d %s\033[0m\n", name, result.IntPart(), baseCurrency)
			} else {
				f, _ := result.Float64()
				fmt.Printf("\033[1;33m%s = %.4f %s\033[0m\n", name, f, baseCurrency)
			}
		} else if res.Dim != DimNone {
			label := ""
			for _, v := range unitRegistry {
				if v.Dimension == res.Dim && v.Factor.Equal(d(1.0)) {
					label = v.Label
					break
				}
			}
			fmt.Printf("\033[1;33m%s = %v %s\033[0m\n", name, res.Value, label)
		} else {
			if res.Value.IsInteger() {
				fmt.Printf("\033[1;33m%s = %d\033[0m\n", name, res.Value.IntPart())
			} else {
				fmt.Printf("\033[1;33m%s = %v\033[0m\n", name, res.Value)
			}
		}
		return false
	}

	res, target, err := evaluate(line)
	if err != nil {
		fmt.Printf("\033[1;31mError:\033[0m %v\n", err)
		return false
	}

	variables["ans"] = res
	variables["_"] = res

	printResult(res, target)
	return false
}

func main() {
	initUnits()

	optY := false
	newArgs := []string{os.Args[0]}
	for i := 1; i < len(os.Args); i++ {
		if os.Args[i] == "-y" {
			optY = true
		} else {
			newArgs = append(newArgs, os.Args[i])
		}
	}
	os.Args = newArgs

	if !optY {
		checkforupdate(UPDATEURL)
	}

	hasArgs := len(os.Args) > 1

	if err := fetchRates(); err != nil && !hasArgs {
		fmt.Printf("\033[1;31mWarning:\033[0m Failed to fetch rates: %v\n", err)
	}

	home, _ := os.UserHomeDir()
	historyFile := filepath.Join(home, ".goca_history")
	variablesFile := filepath.Join(home, ".goca_variables.json")
	functionsFile := filepath.Join(home, ".goca_functions.json")
	if err := loadUserFuncs(functionsFile); err != nil && !hasArgs {
		fmt.Printf("\033[1;31mWarning:\033[0m Failed to load persisted functions: %v\n", err)
	}

	if err := loadVariables(variablesFile); err != nil && !hasArgs {
		fmt.Printf("\033[1;31mWarning:\033[0m Failed to load persisted variables: %v\n", err)
	}

	if hasArgs {
		// Check for -p or --port flag
		for i := 1; i < len(os.Args); i++ {
			arg := os.Args[i]
			if arg == "-p" || arg == "--port" {
				if i+1 < len(os.Args) {
					port := os.Args[i+1]
					startWebServer(port)
					return
				} else {
					fmt.Println("\033[1;31mError:\033[0m Missing port number after -p/--port")
					return
				}
			}
		}

		input := strings.Join(os.Args[1:], " ")
		handleLine(input, false, variablesFile, functionsFile)
		return
	}

	var useReadline = true
	if fi, err := os.Stdin.Stat(); err == nil && (fi.Mode()&os.ModeCharDevice) == 0 {
		useReadline = false
	}

	var rl *readline.Instance
	if useReadline {
		var err error
		rl, err = readline.NewEx(&readline.Config{
			Prompt:          "\033[1;32mgoca>\033[0m ",
			HistoryFile:     historyFile,
			InterruptPrompt: "^C",
			EOFPrompt:       "exit",
			AutoComplete:    &CalcCompleter{},
		})
		if err != nil {
			useReadline = false
		} else {
			defer rl.Close()
		}
	}

	if useReadline {
		fmt.Printf("\033[1;34mgoca v%s\033[0m, type 'help' for examples.\n", Version)
	}

	var scanner *bufio.Scanner
	if !useReadline {
		scanner = bufio.NewScanner(os.Stdin)
	}

	for {
		var line string
		if useReadline {
			var err error
			line, err = rl.Readline()
			if err != nil {
				break
			}
		} else {
			if !scanner.Scan() {
				break
			}
			line = scanner.Text()
		}
		if handleLine(line, useReadline, variablesFile, functionsFile) {
			break
		}
	}
}