--
-- vis-commentary
--
local comment_string = {
    actionscript = '//',
    ada = '--',
    ansi_c = '/*|*/',
    antlr = '//',
    apdl = '!',
    apl = '#',
    applescript = '--',
    asp = '\'',
    autoit = ';',
    awk = '#',
    b_lang = '//',
    bash = '#',
    batch = ':',
    bibtex = '%',
    boo = '#',
    chuck = '//',
    cmake = '#',
    coffeescript = '#',
    context = '%',
    cpp = '//',
    crystal = '#',
    csharp = '//',
    css = '/*|*/',
    cuda = '//',
    dart = '//',
    desktop = '#',
    django = '{#|#}',
    dmd = '//',
    dockerfile = '#',
    dot = '//',
    eiffel = '--',
    elixir = '#',
    erlang = '%',
    faust = '//',
    fennel = ';;',
    fish = '#',
    forth = '|\\',
    fortran = '!',
    fsharp = '//',
    gap = '#',
    gettext = '#',
    gherkin = '#',
    glsl = '//',
    gnuplot = '#',
    go = '//',
    groovy = '//',
    gtkrc = '#',
    haskell = '--',
    html = '<!--|-->',
    icon = '#',
    idl = '//',
    inform = '!',
    ini = '#',
    Io = '#',
    java = '//',
    javascript = '//',
    json = '/*|*/',
    jsp = '//',
    latex = '%',
    ledger = '#',
    less = '//',
    lilypond = '%',
    lisp = ';',
    logtalk = '%',
    lua = '--',
    makefile = '#',
    markdown = '<!--|-->',
    matlab = '#',
    moonscript = '--',
    myrddin = '//',
    nemerle = '//',
    nsis = '#',
    objective_c = '//',
    pascal = '//',
    perl = '#',
    php = '//',
    pico8 = '//',
    pike = '//',
    pkgbuild = '#',
    prolog = '%',
    props = '#',
    protobuf = '//',
    ps = '%',
    pure = '//',
    python = '#',
    rails = '#',
    rc = '#',
    rebol = ';',
    rest = '.. ',
    rexx = '--',
    rhtml = '<!--|-->',
    rstats = '#',
    ruby = '#',
    rust = '//',
    sass = '//',
    scala = '//',
    scheme = ';',
    smalltalk = '"|"',
    sml = '(*)',
    snobol4 = '#',
    sql = '#',
    tcl = '#',
    tex = '%',
    text = '',
    toml = '#',
    vala = '//',
    vb = '\'',
    vbscript = '\'',
    verilog = '//',
    vhdl = '--',
    wsf = '<!--|-->',
    xml = '<!--|-->',
    yaml = '#',
    zig = '//',
    nim = '#',
    julia = '#',
    rpmspec = '#'
}

-- escape all magic characters with a '%'
local function esc(str)
    if not str then return "" end
    return (str:gsub('%%', '%%%%'):gsub('^%^', '%%^'):gsub('%$$', '%%$'):gsub(
               '%(', '%%('):gsub('%)', '%%)'):gsub('%.', '%%.')
               :gsub('%[', '%%['):gsub('%]', '%%]'):gsub('%*', '%%*')
               :gsub('%+', '%%+'):gsub('%-', '%%-'):gsub('%?', '%%?'))
end

-- escape '%'
local function pesc(str)
    if not str then return "" end
    return str:gsub('%%', '%%%%')
end

local function rtrim(s)
    local n = #s
    while n > 0 and s:find("^%s", n) do n = n - 1 end
    return s:sub(1, n)
end

local function comment_line(lines, lnum, prefix, suffix)
    if suffix ~= "" then suffix = " " .. suffix end
    lines[lnum] = string.gsub(lines[lnum], "(%s*)(.*)",
                              "%1" .. pesc(prefix) .. " %2" .. pesc(suffix))
end

local function uncomment_line(lines, lnum, prefix, suffix)
    local match_str = "^(%s*)" .. esc(prefix) .. "%s?(.*)" .. esc(suffix)
    local m = table.pack(lines[lnum]:match(match_str))
    lines[lnum] = m[1] .. rtrim(m[2])
end

local function is_comment(line, prefix)
    return (line:match("^%s*(.+)"):sub(0, #prefix) == prefix)
end

local function toggle_line_comment(lines, lnum, prefix, suffix)
    if not lines or not lines[lnum] then return end
    if not lines[lnum]:match("^%s*(.+)") then return end -- ignore empty lines
    if is_comment(lines[lnum], prefix) then
        uncomment_line(lines, lnum, prefix, suffix)
    else
        comment_line(lines, lnum, prefix, suffix)
    end
end

-- if one line inside the block is not a comment, comment the block.
-- only uncomment, if every single line is comment.
local function block_comment(lines, a, b, prefix, suffix)
    local uncomment = true
    for i = a, b do
        if lines[i]:match("^%s*(.+)") and not is_comment(lines[i], prefix) then
            uncomment = false
        end
    end

    if uncomment then
        for i = a, b do
            if lines[i]:match("^%s*(.+)") then
                uncomment_line(lines, i, prefix, suffix)
            end
        end
    else
        for i = a, b do
            if lines[i]:match("^%s*(.+)") then
                comment_line(lines, i, prefix, suffix)
            end
        end
    end
end

vis:map(vis.modes.NORMAL, "gcc", function()
    local win = vis.win
    local lines = win.file.lines
    local comment = comment_string[win.syntax]
    if not comment then return end
    local prefix, suffix = comment:match('^([^|]+)|?([^|]*)$')
    if not prefix then return end

    for sel in win:selections_iterator() do
        local lnum = sel.line
        local col = sel.col

        toggle_line_comment(lines, lnum, prefix, suffix)
        sel:to(lnum, col) -- restore cursor position
    end

    win:draw()
end, "Toggle comment on a the current line")

local function visual_f(i)
    return function()
        local win = vis.win
        local lines = win.file.lines

        local comment = comment_string[win.syntax]
        if not comment then return end

        local prefix, suffix = comment:match('^([^|]+)|?([^|]*)$')
        if not prefix then return end

        for sel in win:selections_iterator() do
            local r = sel.range
            local lnum = sel.line -- line number of cursor
            local col = sel.col -- column of cursor

            if sel.anchored and r then
                sel.pos = r.start
                local a = sel.line
                sel.pos = r.finish
                local b = sel.line - i

                block_comment(lines, a, b, prefix, suffix)

                sel:to(lnum, col) -- restore cursor position
            end
        end

        win:draw()
        vis.mode = vis.modes.NORMAL -- go to normal mode
    end
end

vis:map(vis.modes.VISUAL_LINE, "gc", visual_f(1),
        "Toggle comment on the selected lines")
vis:map(vis.modes.VISUAL, "gc", visual_f(0),
        "Toggle comment on the selected lines")