SHS/ast/var_table.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 ast

import (
    "os"
    "fmt"
    "math"
    "strconv"
    "strings"
    "gitlab.com/whom/shs/log"
)

/* defines whether or not to synchronize tokens wiht os environment vars
 * will not sync non stringable tokens
 */
var SyncTablesWithOSEnviron = false

/* mapping of key to token.
 */
type VarTable *map[string]*Token

/* retrieve the token cooresponding to a given key
 * if SyncTablesWithOSEnviron is true and no token exists for a key
 * os Environment variables will be searched for the key
 */
func GetVar(arg string, vt VarTable) *Token {
    val, ok := (*vt)[arg]
    if !ok {
        if !SyncTablesWithOSEnviron {
            return nil
        }

        e := os.Getenv(arg)
        if e != "" {
            t := &Token{inner: e}
            if StrIsNumber(e) {
                t.Tag = NUMBER
            } else {
                t.Tag = STRING
            }

            SetVar(arg, t, vt)
            return t
        }
        return nil
    }
    return val
}

/* adds a key->token mapping to the table
 * if SyncTablesWithOSEnviron is true, will also add value to os environment
 * will not do so for non stringable tokens
 */
func SetVar(variable string, value *Token, vt VarTable) {
    (*vt)[variable] = value
    if SyncTablesWithOSEnviron && 
       (value.Tag == NUMBER || value.Tag == STRING) {
        token := value.Value()
        if value.Tag == NUMBER {
            // make sure its an int
            a, err := strconv.ParseFloat(token, 64)
            if err == nil && math.Mod(a, 1.0) == 0 {
                token = fmt.Sprintf("%d", int(a))
            }
        }
        os.Setenv(variable, token)
    }
}

/* lists all vars in tables
 */
func ListVars(vt VarTable) []string {
    keys := make([]string, len(*vt))
    i := 0
    for k := range *vt {
        keys[i] = k
    }

    return keys
}

/* if SyncTablesWithOSEnviron is true 
 * function will put ever environment variable into VarTable
 */
func InitVarTable(table VarTable) {
    if !SyncTablesWithOSEnviron {
        return
    }

    for _, val := range os.Environ() {
        variable := strings.Split(val, "=")
        t := &Token{inner: variable[1]}
        if StrIsNumber(variable[1]) {
            t.Tag = NUMBER
        } else {
            t.Tag = STRING
        }

        if variable[0] == "HOME" {
            SetVar("~", t, table)
        }
        SetVar(variable[0], t, table)
    }
}

// Dont do this on var tables youve already called InitVarTable on.... please....
// This will pull currently contained variables OUT of the operating env
func DeleteVarTable(table VarTable) {
    for key, _ := range (*table) {
        // from what I can tell, theres not much we can do if this fails
        err := os.Unsetenv(key)
        if err != nil {
            log.Log(log.DEBUG, "Failed to remove " + key + " from env: " + err.Error(), "vartable")
        }
    }
}

/* removes var from vartable
 * if SyncTablesWithOSENviron is true, also unsets environment variable
 */
func RemoveVar(arg string, table VarTable) {
    if SyncTablesWithOSEnviron {
        err := os.Unsetenv(arg)
        if err != nil {
            log.Log(log.DEBUG,
                "Failed to remove "+arg+" from env: "+err.Error(),
                "vartable")
        }
    }
    delete(*table, arg)
}