#!/bin/env lua
-- Trimmed down cat(1) utility.
--
-- Concatenate files to stdout, making sure bytes are actually written
-- out successfully.
--
-- SYNOPSIS:
-- cat.lua [-u] <FILES...>
--
-- NOTE: utility doesn't explicitly allow to concatenate stdin.
--
-- Author: Lorenzo Cogotti, The DoubleFourteen Code Forge

local osx = require 'osx'
local io = require 'io'

local uflag = false

local function cat(path)
    local ferr = io.stderr

    local f, err = io.open(path, 'r')
    if err then
        ferr:write(err, "\n")
        return false
    end

    local success = true  -- unless it happens to be a failure
    local fout = io.stdout

    while true do
        local buf, err = f:read(4096)
        if err then
            ferr:write(err, "\n")
            success = false
        end
        if not buf then
            break  -- done with file
        end
        assert(fout:write(buf))
    end
    f:close()

    assert(fout:flush())
    if not osx.isatty(fout) then
        assert(osx.commit(fout))
    end
    return success
end

local function parseargs(...)
    local files = {}
    for i = 1, select('#', ...) do
        local arg = select(i, ...)
        if arg == '-u' then
            uflag = true
        else
            files[#files+1] = arg
        end
    end
    if #files == 0 then
        error("Missing file arguments")
    end
    return files
end

local files = parseargs(...)

io.stdout:setvbuf(uflag and 'no' or 'full')

local success = true
for _, path in ipairs(files) do
    if not cat(path) then
        success = false
    end
end

osx.exit(success and 0 or 1)