/*   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/peterh/liner"
    "gitlab.com/whom/shs/ast"
    "gitlab.com/whom/shs/log"
    "gitlab.com/whom/shs/util"
    "gitlab.com/whom/shs/stdlib"
    "gitlab.com/whom/shs/config"
)

const (
    def_prompt  string = "λ "
)


// useful for when input contains escape sequences
// not checking delims cause thats up to the user who defines their prompts
func parseString(in string) string {
    in = "\"" + in + "\""
    out, err := strconv.Unquote(in)
    if err != nil {
        log.Log(log.ERR,
            "Couldnt parse (pre?)prompt",
            "init")
        return ""
    }

    return out
}

func setLogLvl(vars ast.VarTable) {
    var loglvl string

    loglvl_t := ast.GetVar("SH_LOGGING", vars)
    if loglvl_t != nil {
        loglvl = loglvl_t.Value()
    }

    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() {
    var prompt string
    var debug string
    var hist string
    no_hist := false

    ast.SyncTablesWithOSEnviron = true
    ast.ExecWhenFuncUndef = true

    stdlib.InitShellFeatures()
    defer stdlib.TeardownShell()

    vars, funcs := config.InitFromConfig(".shsrc")
    debug_t := ast.GetVar("SH_DEBUG_MODE", vars)
    if debug_t != nil {
        debug = debug_t.Value()
    }

    hist_t := ast.GetVar("SH_HIST_FILE", vars)
    if hist_t != nil {
        hist = hist_t.Value()
    } else {
        no_hist = true
    }

    dyn_prompt := ast.GetFunction("_SH_PROMPT", funcs)
    if dyn_prompt == nil || dyn_prompt.Args != 0 {
        dyn_prompt = nil
    }

    prompt_t := ast.GetVar("SHS_STATIC_PROMPT", vars)
    if prompt_t != nil {
        prompt = parseString(prompt_t.Value())
    } else {
        prompt = def_prompt
    }

    line := liner.NewLiner()
    defer line.Close()

    line.SetCtrlCAborts(true)
    line.SetCompleter(func(line string) (c []string) {
        return util.ShellCompleter(line, vars, funcs)
    })

    var histFile *os.File
    var err error
    if !no_hist {
        histFile, err = os.Open(hist)
        if err == nil {
            line.ReadHistory(histFile)
        } else {
            log.Log(log.ERR,
                "couldnt read history: " + err.Error(),
                "repl")
        }
        defer histFile.Close()
    }

    for {
        setLogLvl(vars)
        var prePrompt string
        if dyn_prompt != nil {
            p_tok := dyn_prompt.CallFunction(nil, vars, funcs)
            if p_tok != nil && p_tok.Tag == ast.STRING {
                prePrompt = parseString(p_tok.Value())
            }
        }

        fmt.Printf(prePrompt)
        text, err := line.Prompt(prompt)
        if err != nil && err != liner.ErrPromptAborted{
            log.Log(log.ERR, "couldnt read user input: " + err.Error(), "repl")
            continue
        }

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

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

        result := userInput.Eval(funcs, vars, false)
        if result != nil {
            for i := result; i != nil; i = i.Next {
                fmt.Printf(i.String() + " ")
            }
        }

        fmt.Printf("\n")
    }
}