scripts/index-cmd/init.lua

local modname = ...
module(modname, package.seeall)
-- local ffi = require('ffi')
local host = require('host')
local window = require('host.window')

local getch
local ungetch
local peekch
local tokenstack = {} -- only used to show the command-line user what he's expected to close
-- actual parser state is kept on call stack
do
    local buffer = {}
    local newline = true

    local function getch_raw()
        if newline then
            if #tokenstack > 0 then
                host.write(' ')
                host.write(table.concat(tokenstack, ' | '))
                host.write(' >> ')
            else
                host.write('>> ')
            end
            newline = false
        end
        local ch = host.getchar()
        if ch == '\n' then
            newline = true
        end
        return ch
    end

    function getch()
        local ch
        if #buffer > 0 then
            ch = table.pop(buffer)
        else
            ch = getch_raw()
        end
        return ch
    end

    function ungetch(ch)
        table.append(buffer, ch)
    end

    function peekch()
        local ch = getch()
        ungetch(ch)
        return ch
    end
end

local obtaintoken

local function obtainstringelement()
    local ch = getch()
    if ch == '\\' then
        ch = ch .. getch()
    end
    return ch
end

local function obtainstring()
    local open = getch()
    table.append(tokenstack, open)
    local content = {open}
    while true do
        local element = obtainstringelement()
        table.append(content, element)
        if element == open then
            break
        elseif element == '\n' then
            if peekch() == '\n' then
                table.append(content, getch())
                break
            end
        end
    end
    table.pop(tokenstack)
    return table.concat(content)
end

local function obtainlongstring(level)
    local open = '[' .. string.rep('=', level) .. '['
    local content = {open}
    table.append(tokenstack, open)
    while true do
        local ch = getch()
        table.append(content, ch)
        if ch == ']' then
            for i = 1, level do
                ch = getch()
                if ch == '=' then
                    table.append(content, ch)
                else
                    ungetch(ch)
                    ch = nil
                    break
                end
            end
            if ch then
                ch = getch()
                if ch == ']' then
                    table.append(content, ch)
                    break
                else
                    ungetch(ch)
                end
            end
        elseif ch == '\n' then
            if peekch() == '\n' then
                table.append(content, getch())
                break
            end
        end
    end
    table.pop(tokenstack)
    return table.concat(content)
end

local letter = {
    ['_'] = true,
}
local letterordigit = {
    ['_'] = true,
}
for i = string.byte('A'), string.byte('Z') do
    letter[string.char(i)] = true
    letterordigit[string.char(i)] = true
end
for i = string.byte('a'), string.byte('z') do
    letter[string.char(i)] = true
    letterordigit[string.char(i)] = true
end
for i = string.byte('0'), string.byte('9') do
    letterordigit[string.char(i)] = true
end

local wordtable = {
    ['do'] = 'end',
    ['function'] = 'end',
    ['if'] = 'end',
    ['repeat'] = 'until',
}

local function obtainwordbody(open)
    table.append(tokenstack, open)
    local close = wordtable[open]
    local content = {open}
    while true do
        local token = obtaintoken()
        table.append(content, token)
        if token == close then
            break
        elseif token == '\n' then
            if peekch() == '\n' then
                table.append(content, getch())
                break
            end
        end
    end
    table.pop(tokenstack)
    return table.concat(content)
end

local function obtainword()
    local word = ''
    while true do
        local ch = getch()
        if letterordigit[ch] then
            word = word .. ch
        else
            ungetch(ch)
            break
        end
    end
    if wordtable[word] then
        return obtainwordbody(word)
    else
        return word
    end
end

local brackettable = {
    ['('] = ')',
    ['['] = ']',
    ['{'] = '}',
}

local function obtainbracket()
    local open = getch()
    table.append(tokenstack, open)
    local close = brackettable[open]
    local content = {open}
    while true do
        local token = obtaintoken()
        table.append(content, token)
        if token == close then
            break
        elseif token == '\n' then
            if peekch() == '\n' then
                table.append(content, getch())
                break
            end
        end
    end
    table.pop(tokenstack)
    return table.concat(content)
end

local tokentable = {
    ['\''] = obtainstring,
    ['"'] = obtainstring,
}
for ch in pairs(letter) do
    tokentable[ch] = obtainword
end
for ch in pairs(brackettable) do
    tokentable[ch] = obtainbracket
end

tokentable['['] = function()
    local open = getch()
    local mid = {}
    for i = 1, 16 do
        local ch = getch()
        if ch == '[' then
            return obtainlongstring(#mid)
        end
        table.append(mid, ch)
        if ch ~= '=' then
            break
        end
    end
    for i = #mid, 1, -1 do
        ungetch(mid[i])
    end
    ungetch(open)
    return obtainbracket()
end

function obtaintoken()
    local ch = peekch()
    local tfunc = tokentable[ch]
    if tfunc then
        return tfunc()
    else
        return getch()
    end
end

local function obtaininput()
    local str = ''
    while true do
        local token = obtaintoken()
        if token == '\n' then
            break
        end
        str = str .. token
    end
    return str
end

function register()
    log('entered interactive mode')
    local terminate = false

    local function exit()
        terminate = true
    end

    local fenv = setmetatable({exit = exit}, {__index = _G})
    fenv._ENV = fenv
    print('Interactive input. Call "exit()" to continue\n')

    while not terminate do
        local str = obtaininput()
        local func, err = loadstring('print(' .. str .. ')', nil, nil, fenv)
        if func then
            local suc, err = pcall(func)
            if not suc then
                print(err)
            end
        else
            func, err = loadstring(str, nil, nil, fenv)
            if func then
                local suc, err = pcall(func)
                if not suc then
                    print(err)
                end
            else
                print(err)
            end
        end
    end
    log('exited from interactive mode')
    window:finish()
end

function unregister()
end