#!/bin/env lua
-- Basic Unix-style directory listing.
-- Demonstrates low-level raw use of a Dir, in order to list even . and .. to
-- output.
--
-- NOTE: the simplistic argument parser doesn't handle merged options like -ht. 
--
-- Example uses:
-- lua ls.lua
-- lua ls.lua -a ..
-- lua ls.lua -a -h src
-- lua ls.lua -a -t a.dir b.dir c.dir
--
-- Supported options:
-- -a list hidden files
-- -t sort by time, most recent first
-- -S sort by size, largest first
-- -h print size next to each file in kilobytes (1024)
--
-- Author: Lorenzo Cogotti, The DoubleFourteen Code Forge

local osx = require 'osx'
local io = require 'io'
local write = io.write

local sep = osx.sep
local aflag = false  -- list hidden
local tflag = false  -- sort by time
local Sflag = false  -- sort by size
local hflag = false  -- print size, human readable (equivalent to -sh)

local function parseargs(...)
    local args = {}

    for i = 1,select('#', ...) do
        local arg = select(i, ...)

        if arg == '-a' then
            aflag = true
        elseif arg == '-t' then
            tflag, Sflag = true, false
        elseif arg == '-S' then
            Sflag, tflag = true, false
        elseif arg == '-h' then
            hflag = true
        else
            args[#args+1] = arg
        end
    end
    if #args == 0 then
        args = { "." } -- current directory by default
    end
    return args
end

local function ksize(sz)
    sz = sz / 1024

    if sz > 0 then
        return ("%.1fK"):format(sz)
    else
        return "0"
    end
end

local function listfilenames(filenames, bufs, total)
    table.sort(filenames) -- always sort by name

    if Sflag then
        table.sort(filenames, function (a, b)
            a, b = bufs[a], bufs[b]

            local asize = a.size or -1
            local bsize = b.size or -1
            return asize > bsize -- sort by size, largest first
        end)
    elseif tflag then
        table.sort(filenames, function(a, b)
            a, b = bufs[a], bufs[b]

            local atime = a.mtime or -1
            local btime = b.mtime or -1
            return atime > btime  -- sort by time, latest first
        end)
    end

    if hflag then
        write(ksize(total), " total\n")
    end
    for _, filename in ipairs(filenames) do
        local buf = bufs[filename]

        if hflag then
            write(ksize(buf.size or 0), " ")
        end
        write(filename, "\n")
    end
end

local function ls(path)
    local dir, err = osx.opendir(path)
    if not dir then
        io.stderr:write(err, "\n")
        return
    end

    local filenames = {}
    local bufs = {}
    local total = 0

    while true do
    :: nextfilename ::
        local filename, err = dir:readdir()
        if err then
            -- Report, but tolerate error
            io.stderr:write(path, ": ", err, "\n")
        end
        if not filename then
            break  -- done with this dir
        end
        if filename:sub(1, 1) == '.' and not aflag then
            goto nextfilename  -- skip hidden
        end

        -- stat() file, update counters and store for listing
        local filepath = path..sep..filename
        local buf, err = osx.stat(filepath)
        if not buf then
            io.stderr:write(filepath, ": ", err, "\n")
            goto nextfilename
        end

        total = total + (buf.size or 0)
        filenames[#filenames+1] = filename
        bufs[filename] = buf
    end

    -- Print file list
    listfilenames(filenames, bufs, total)
    dir:close()  -- NOTE: could have marked this with <close>
end

local args = parseargs(...)
for _,path in ipairs(args) do
    ls(path)
end