// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// main.go
package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strings"

	"git.portale-stac.it/go-pkg/expr"
	"git.portale-stac.it/go-pkg/utils"

	// https://pkg.go.dev/github.com/ergochat/readline#section-readme
	"github.com/ergochat/readline"
)

const (
	intro = PROGNAME + ` -- Expressions calculator ` + VERSION + `
	Based on the Expr package ` + EXPR_VERSION + `
	Type help to get the list of available commands
	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
`
	mainPrompt = ">>> "
	contPrompt = "... "

	historyFile = "~/.expr_history"
)

type commandFunction func(ctx expr.ExprContext, args []string) (err error)

type command struct {
	name        string
	description string
	code        commandFunction
}

func (cmd *command) exec(ctx expr.ExprContext, args []string) (err error) {
	return cmd.code(ctx, args)
}

type commandHandler struct {
	commands map[string]*command
	// ctx      expr.ExprContext
}

func NewCommandHandler() *commandHandler {
	return &commandHandler{
		commands: make(map[string]*command),
	}
}

// func (h *commandHandler) setContext(ctx expr.ExprContext) {
// 	h.ctx = ctx
// }

func (h *commandHandler) add(name, description string, f commandFunction) {
	h.commands[name] = &command{name: name, description: description, code: f}
}

func (h *commandHandler) get(cmdLine string) (cmd *command, args []string) {
	if len(cmdLine) > 0 {
		tokens := strings.Split(cmdLine, " ")
		name := tokens[0]
		args = make([]string, 0, len(tokens)-1)
		if cmd = h.commands[name]; cmd != nil && len(tokens) > 1 {
			for _, tk := range tokens[1:] {
				if tk != "" {
					args = append(args, tk)
				}
			}
		}
	}
	return
}

// ------

type Options struct {
	printTree        bool
	printPrefix      bool
	forceInteractive bool
	builtin          []any
	expressions      []io.Reader
	formOpt          expr.FmtOpt
	baseVerb         string
	base             int
	output           bool
	rcCount          int
}

func NewOptions() *Options {
	return &Options{
		expressions: make([]io.Reader, 0),
		builtin:     make([]any, 0),
		formOpt:     expr.Base10,
		baseVerb:    "%d",
		base:        10,
		output:      true,
		rcCount:     0,
	}
}

func errOptValueRequired(opt string) error {
	return fmt.Errorf("option %q requires a value", opt)
}

func about() string {
	return PROGNAME + " -- " + VERSION + "; Expr package " + EXPR_VERSION
}

func (opt *Options) loadRc() {
	var rcPath string
	var fh *os.File
	var err error
	if rcPath, err = utils.ExpandPath("~/.dev-expr.rc"); err != nil {
		return
	}
	if fh, err = os.Open(rcPath); err == nil {
		opt.expressions = append(opt.expressions, fh)
		opt.rcCount++
	}
}

func (opt *Options) parseArgs() (err error) {
	for i := 1; i < len(os.Args) && err == nil; i++ {
		arg := os.Args[i]
		switch arg {
		case "-i":
			opt.forceInteractive = true
		case "-t":
			opt.printTree = true
		case "-p":
			opt.printPrefix = true
		case "-e":
			if i+1 < len(os.Args) {
				i++
				spec := os.Args[i]
				if strings.HasPrefix(spec, "@") {
					var f *os.File
					if f, err = os.Open(spec[1:]); err == nil {
						opt.expressions = append(opt.expressions, f)
					} else {
						return
					}
				} else {
					opt.expressions = append(opt.expressions, strings.NewReader(spec))
				}
			} else {
				err = errOptValueRequired(arg)
			}
		case "-b":
			if i+1 < len(os.Args) {
				i++
				specs := strings.Split(os.Args[i], ",")
				if len(specs) == 1 {
					opt.builtin = append(opt.builtin, specs[0])
				} else {
					opt.builtin = append(opt.builtin, specs)
				}
			} else {
				err = errOptValueRequired(arg)
			}
		case "-m", "--modules":
			expr.IterateBuiltinModules(func(name, description string, _ bool) bool {
				fmt.Printf("%20q: %s\n", name, description)
				return true
			})
			os.Exit(0)
		case "--noout":
			opt.output = false
		case "-h", "--help", "help":
			cmdHandler.help()
			os.Exit(0)
		case "-v", "--version", "version", "about":
			fmt.Println(about())
			os.Exit(0)
		default:
			err = fmt.Errorf("invalid option nr %d %q", i+1, arg)
		}
	}
	return
}

// ------
var cmdHandler *commandHandler

func (h *commandHandler) help() {
	fmt.Fprintln(os.Stderr, `--- REPL commands:`)
	for _, cmd := range h.commands {
		fmt.Fprintf(os.Stderr, "%12s -- %s\n", cmd.name, cmd.description)
	}
	fmt.Fprint(os.Stderr, `
--- Command line options:
    -b <builtin>       Import builtin modules.
                       <builtin> can be a list of module names or a glob-pattern.
                       Use the special value 'all' or the pattern '*' to import all modules.
    -e <expression>    Evaluate <expression> instead of standard-input
    -i                 Force REPL operation when all -e occurences have been processed
    -h, --help, help   Show this help menu
    -m, --modules      List all builtin modules
    --noout            Disable printing of expression results
    -p                 Print prefix form
    -t                 Print tree form
    -v, --version      Show program version
`)

}

func importBuiltins(opt *Options) (err error) {
	for _, spec := range opt.builtin {
		if moduleSpec, ok := spec.(string); ok {
			if moduleSpec == "all" {
				moduleSpec = "*"
			}
			_, err = expr.ImportInContextByGlobPattern(moduleSpec)
		} else if moduleSpec, ok := spec.([]string); ok {
			notFoundList := make([]string, 0)
			for _, name := range moduleSpec {
				if !expr.ImportInContext(name) {
					notFoundList = append(notFoundList, name)
				}
			}
			if len(notFoundList) > 0 {
				err = fmt.Errorf("not found modules: %s", strings.Join(notFoundList, ","))
			}
		}
	}
	return
}

func initReadlineConfig(cfg *readline.Config) {
	if histfile, err := utils.ExpandPath(historyFile); err == nil {
		cfg.HistoryFile = histfile
	}
	cfg.Undo = true
	cfg.DisableAutoSaveHistory = true

}

func goInteractiveReadline(opt *Options, ctx expr.ExprContext, r io.Reader) {
	var sb strings.Builder
	var cfg readline.Config
	initReadlineConfig(&cfg)
	rl, err := readline.NewFromConfig(&cfg)
	if err != nil {
		goInteractive(opt, ctx, r)
		return
	}
	defer rl.Close()

	fmt.Print(intro)
	rl.SetPrompt(mainPrompt)
	for line, err := rl.ReadLine(); err == nil; line, err = rl.ReadLine() {
		if len(line) > 0 && line[len(line)-1] == '\\' {
			sb.WriteString(line[0 : len(line)-1])
			rl.SetPrompt(contPrompt)
			continue
		}
		rl.SetPrompt(mainPrompt)
		sb.WriteString(line)
		source := strings.TrimSpace(sb.String())
		if source != "" && !strings.HasPrefix(source, "//") {
			if cmd, args := cmdHandler.get(source); cmd != nil {
				rl.SaveToHistory(source)
				if err = cmd.exec(ctx, args); err != nil {
					break
				}
			} else {
				rl.SaveToHistory(source)
				r := strings.NewReader(source)
				compute(opt, ctx, r, true)

			}
		}
		sb.Reset()
	}
	fmt.Println()
}

func goInteractive(opt *Options, ctx expr.ExprContext, r io.Reader) {
	var sb strings.Builder
	fmt.Print(intro)
	fmt.Print(mainPrompt)
	reader := bufio.NewReaderSize(r, 1024)
	for line, err := reader.ReadString('\n'); err == nil && line != "exit\n"; line, err = reader.ReadString('\n') {
		if strings.HasSuffix(line, "\\\n") {
			sb.WriteString(line[0 : len(line)-2])
			fmt.Print(contPrompt)
			continue
		}
		sb.WriteString(line)
		source := strings.TrimSpace(sb.String())
		// fmt.Printf("source=%q\n", source)
		if source != "" && !strings.HasPrefix(source, "//") {
			if cmd, args := cmdHandler.get(source); cmd != nil {
				if err = cmd.exec(ctx, args); err != nil {
					break
				}
			} else {
				r := strings.NewReader(source)
				compute(opt, ctx, r, true)
			}
		}
		sb.Reset()
		fmt.Print(mainPrompt)
	}
	fmt.Println()
}

func goBatch(opt *Options, ctx expr.ExprContext, r io.Reader) {
	var sb strings.Builder
	reader := bufio.NewReaderSize(r, 1024)
	for line, err := reader.ReadString('\n'); err == nil && line != "exit\n"; line, err = reader.ReadString('\n') {
		if strings.HasSuffix(line, "\\\n") {
			sb.WriteString(line[0 : len(line)-2])
			continue
		}
		sb.WriteString(line)
		source := strings.TrimSpace(sb.String())
		// fmt.Printf("source=%q\n", source)
		if source != "" && !strings.HasPrefix(source, "//") {
			if cmd, args := cmdHandler.get(source); cmd != nil {
				if err = cmd.exec(ctx, args); err != nil {
					break
				}
			} else {
				r := strings.NewReader(source)
				compute(opt, ctx, r, false)
			}
		}
		sb.Reset()
	}
}

func compute(opt *Options, ctx expr.ExprContext, r io.Reader, outputEnabled bool) {
	scanner := expr.NewScanner(r, expr.DefaultTranslations())
	parser := expr.NewParser()

	if ast, err := parser.Parse(scanner); err == nil {
		if opt.printPrefix {
			fmt.Println(ast)
		}
		if opt.printTree {
			r := expr.NewExprReticle(ast)
			fmt.Println(r.String())
		}

		outputEnabled = outputEnabled && opt.output
		if result, err := ast.Eval(ctx); err == nil {
			if outputEnabled {
				printResult(opt, result)
			}
		} else {
			fmt.Fprintln(os.Stderr, "Eval Error:", err)
		}
	} else {
		fmt.Fprintln(os.Stderr, "Parse Error:", err)
	}
}

func printResult(opt *Options, result any) {
	if f, ok := result.(expr.Formatter); ok {
		fmt.Println(f.ToString(opt.formOpt))
	} else if expr.IsInteger(result) {
		fmt.Printf(opt.baseVerb, result)
		fmt.Println()
	} else if expr.IsString(result) {
		fmt.Printf("\"%s\"\n", result)
	} else {
		fmt.Println(result)
	}
}

func isReaderTerminal(r io.Reader) bool {
	if fh, ok := r.(*os.File); ok {
		return utils.StreamIsTerminal(fh)
	}
	return false
}

func registerLocalFunctions(ctx expr.ExprContext) {
	aboutFunc := func(ctx expr.ExprContext, name string, args []any) (result any, err error) {
		result = about()
		return
	}

	ctrlListFunc := func(ctx expr.ExprContext, name string, args []any) (result any, err error) {
		vars := ctx.EnumVars(func(name string) bool {
			return len(name) > 0 && name[0] == '_'
		})
		result = expr.ListFromStrings(vars)
		return
	}

	ctrlFunc := func(ctx expr.ExprContext, name string, args []any) (result any, err error) {
		varName, _ := args[0].(string)
		if len(args) == 1 {
			result = expr.GlobalCtrlGet(varName)
		} else {
			result = expr.GlobalCtrlSet(varName, args[1])
		}
		return
	}

	envSetFunc := func(ctx expr.ExprContext, name string, args []any) (result any, err error) {
		var varName, value string
		var ok bool
		if varName, ok = args[0].(string); !ok {
			err = expr.ErrExpectedGot(name, expr.TypeString, args[0])
			return
		}
		if value, ok = args[1].(string); !ok {
			err = expr.ErrExpectedGot(name, expr.TypeString, args[1])
			return
		}
		if err = os.Setenv(varName, value); err == nil {
			result = value
		}
		return
	}

	envGetFunc := func(ctx expr.ExprContext, name string, args []any) (result any, err error) {
		var varName string
		var ok bool
		if varName, ok = args[0].(string); !ok {
			err = expr.ErrExpectedGot(name, expr.TypeString, args[0])
			return
		}

		if result, ok = os.LookupEnv(varName); !ok {
			err = fmt.Errorf("environment variable %q does not exist", varName)
		}
		return
	}

	ctx.RegisterFunc("about", expr.NewGolangFunctor(aboutFunc), expr.TypeString, []expr.ExprFuncParam{})
	ctx.RegisterFunc("ctrlList", expr.NewGolangFunctor(ctrlListFunc), expr.TypeListOfStrings, []expr.ExprFuncParam{})
	ctx.RegisterFunc("ctrl", expr.NewGolangFunctor(ctrlFunc), expr.TypeAny, []expr.ExprFuncParam{
		expr.NewFuncParam("prop"),
		expr.NewFuncParamFlag(expr.ParamValue, expr.PfOptional),
	})
	ctx.RegisterFunc("envSet", expr.NewGolangFunctor(envSetFunc), expr.TypeString, []expr.ExprFuncParam{
		expr.NewFuncParam(expr.ParamName),
		expr.NewFuncParam(expr.ParamValue),
	})
	ctx.RegisterFunc("envGet", expr.NewGolangFunctor(envGetFunc), expr.TypeString, []expr.ExprFuncParam{
		expr.NewFuncParam(expr.ParamName),
	})

}

var opt *Options

func main() {
	opt = NewOptions()
	opt.loadRc()
	if err := opt.parseArgs(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	if err := importBuiltins(opt); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	ctx := expr.NewSimpleStore()
	registerLocalFunctions(ctx)

	if len(opt.expressions) == opt.rcCount || opt.forceInteractive {
		opt.expressions = append(opt.expressions, os.Stdin)
	}

	for _, input := range opt.expressions {
		if isReaderTerminal(input) {
			goInteractiveReadline(opt, ctx, input)
		} else {
			goBatch(opt, ctx, input)
			if f, ok := input.(*os.File); ok {
				f.Close()
			}
		}
	}
	if opt.output {
		printResult(opt, ctx.GetLast())
	}
}

// --------

func cmdExit(ctx expr.ExprContext, args []string) (err error) {
	return io.EOF
}

func cmdHelp(ctx expr.ExprContext, args []string) (err error) {
	cmdHandler.help()
	return
}

func cmdMultiLine(ctx expr.ExprContext, args []string) (err error) {
	if opt.formOpt&expr.MultiLine == 0 {
		opt.formOpt |= expr.MultiLine
	} else {
		opt.formOpt &= ^expr.MultiLine
	}
	return
}

func cmdTty(ctx expr.ExprContext, args []string) (err error) {
	if opt.formOpt&expr.TTY == 0 {
		opt.formOpt |= expr.TTY
	} else {
		opt.formOpt &= ^expr.TTY
	}
	return
}

func cmdSource(ctx expr.ExprContext, args []string) (err error) {
	var fh *os.File
	for _, arg := range args {
		length := len(arg)
		if length == 0 {
			continue
		}
		if length >= 2 {
			if (arg[0] == '"' && arg[length-1] == '"') || arg[0] == '\'' && arg[length-1] == '\'' {
				arg = arg[1 : length-1]
			}
		}
		if fh, err = os.Open(arg); err == nil {
			goBatch(opt, ctx, fh)
			fh.Close()
		} else {
			break
		}
	}
	return
}

func cmdModules(ctx expr.ExprContext, args []string) (err error) {
	expr.IterateBuiltinModules(func(name, description string, imported bool) bool {
		var check rune = ' '
		if imported {
			check = '*'
		}
		fmt.Printf("%c %20q: %s\n", check, name, description)
		return true
	})
	return
}

func cmdBase(ctx expr.ExprContext, args []string) (err error) {
	if len(args) == 0 {
		fmt.Println(opt.base)
	} else if args[0] == "2" {
		opt.baseVerb = "0b%b"
		opt.base = 2
	} else if args[0] == "8" {
		opt.baseVerb = "0o%o"
		opt.base = 8
	} else if args[0] == "10" {
		opt.baseVerb = "%d"
		opt.base = 10
	} else if args[0] == "16" {
		opt.baseVerb = "0x%x"
		opt.base = 16
	} else {
		err = fmt.Errorf("invalid number base %s", args[0])
	}
	return
}

func cmdOutput(ctx expr.ExprContext, args []string) (err error) {
	var outputArg string
	if len(args) == 0 {
		outputArg = "status"
	} else {
		outputArg = strings.ToLower(args[0])
	}
	switch outputArg {
	case "on":
		opt.output = true
	case "off":
		opt.output = false
	case "status":
		if opt.output {
			fmt.Println("on")
		} else {
			fmt.Println("off")
		}
	default:
		err = fmt.Errorf("output: unknown option %q", outputArg)
	}
	return
}

//------------------

func init() {
	cmdHandler = NewCommandHandler()
	cmdHandler.add("base", "Set the integer output base: 2, 8, 10, or 16", cmdBase)
	cmdHandler.add("exit", "Exit the program", cmdExit)
	cmdHandler.add("help", "Show command list", cmdHelp)
	cmdHandler.add("ml", "Enable/Disable multi-line output", cmdMultiLine)
	cmdHandler.add("mods", "List builtin modules", cmdModules)
	cmdHandler.add("output", "Enable/Disable printing expression results. Options 'on', 'off', 'status'", cmdOutput)
	cmdHandler.add("source", "Load a file as input", cmdSource)
	cmdHandler.add("tty", "Enable/Disable ansi output", cmdTty)
}