SHS/cmd/shs_repl.go

/*   SHS: Syntactically Homogeneous Shell
 *   Copyright (C) 2019  Aidan Hahn
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package main

import (
    "os"
    "fmt"
    "strconv"
    "github.com/chzyer/readline"
    "gitlab.com/whom/shs/ast"
    "gitlab.com/whom/shs/log"
    "gitlab.com/whom/shs/stdlib"
)

const (
    def_prompt  string = "λ "
)

func setLogLvl() {
    loglvl := os.Getenv("SH_LOGGING")
    if loglvl != "" {
        llvl, err := strconv.ParseInt(loglvl, 10, 8)
        if err != nil {
            log.Log(log.ERR,
            "couldnt parse log level: " + err.Error(),
                    "init")
        } else {
            log.SetLogLvl(llvl)
        }
    }
}

func main() {
    debug  := os.Getenv("SH_DEBUG_MODE")
    hist   := os.Getenv("SH_HIST_FILE")
    prompt := os.Getenv("SHS_SH_PROMPT")

    var vars ast.VarTable
    var funcs ast.FuncTable

    funcs = stdlib.GenFuncTable()
    vars = &map[string]*ast.Token{}
    ast.InitVarTable(vars)
    ast.SyncTablesWithOSEnviron = true

    var err error

    if prompt == "" {
        prompt = def_prompt
    }

    rl, err := readline.NewEx(&readline.Config{
        Prompt: prompt,
        HistoryFile: hist,
        InterruptPrompt: "^C",
    })

    defer rl.Close()
    if err != nil {
        log.Log(log.ERR, "Couldnt initialize readline: " + err.Error(), "repl")
        return
    }

    for {
        setLogLvl()
        text, err := rl.Readline()
        if err != nil {
            log.Log(log.ERR, "couldnt read user input: " + err.Error(), "repl")
        }

        userInput := ast.Lex(text)
        if userInput == nil {
            // errors handled in Lex
            // TODO: return an error instead
            continue
        }

        if debug != "" {
            ast.PrintSExprsIndividually(userInput)
        }

        result, unwrap := userInput.Eval(funcs, vars)
        if result != nil {
            if result.Tag == ast.LIST && unwrap {
                result = result.Inner.(*ast.Token)
            }

            for i := result; i != nil; i = i.Next {
                fmt.Printf(i.String() + " ")
            }
        }

        fmt.Printf("\n")
    }
}