#!/usr/bin/lua

require 'lfs'

-- Path to where packages are located
REPO = 'packages'
-- List of packages (e.g. loaded from dist manifest)
PACKAGES = {
    p1 = true, p2 = true, p3 = true,
}

function git(...)
    local args = {...}
    table.insert(args, 1, 'git')
    local cmd = table.concat(args, ' ')
    print('Executing:', cmd)
    os.execute(cmd)
end

-- Check, whether the current directory has a repo. If not, creates the .last
-- file, which contains the number of the last tag, and adds it to .gitignore
if not lfs.attributes('.last') then
    local f = io.open('.last', 'w')
    f:write('0')
    f:close()
    f = io.open('.gitignore', 'w')
    f:write('.last\n')
    f:close()
    git "init -q"
    git "add .gitignore"
    git "commit -q -m 'Versioning started'"
end

-- Commits using `comment` and creates the next tag (1, 2, 3, ...)
-- and writes the new number in .last
function createTag(comment)
    git("commit -q -m", ('%q'):format(comment))

    local f = io.open('.last')
    local tagno = f:read('*n')
    tagno = tagno + 1
    f:close()
    
    git("tag", tagno)

    f = io.open('.last', 'w')
    f:write(tagno)
    f:close()
end

local command = arg[1]

if command == 'install' then
    local package = arg[2]
    assert(package, "Usage: gitdist install package")
    assert(PACKAGES[package], "Package " .. package .. " does not exist")
    git("remote", "add", package, REPO .. '/' .. package)
    git("fetch", "-q", package)
    git("merge", "-q --no-commit", package..'/master')
    createTag("Installed "..package)
elseif command == 'uninstall' then
    local package = arg[2]
    assert(package, "Usage: gitdist uninstall package")
    createTag("Uninstalled "..package)
elseif command =='clean' then
    os.execute('rm -rf .git .last')
end