Patch Program

-- Patch
-- By KillaVanilla

local args = {...}

if #args < 2 then
    print("patch - change files according to a patchfile")
    print(string.rep("=", term.getSize()))
    print("USAGE: <old file> <patchfile>")
    return
end

assert(fs.exists(args[1]), args[1].." does not exist!")

-- read lines:
local f = fs.open(args[1], "r")
local lines = {}
local last_pause = os.clock()
while true do
    local line = f.readLine()
    if line then
        table.insert(lines, line)
    else
        break
    end
    if (os.clock() - last_pause) >= 2.8 then
        os.queueEvent("")
        os.pullEvent("")
        last_pause = os.clock()
    end
end
f.close()

local f = fs.open(args[2], "r")
local patch_lines = {}
local last_pause = os.clock()
while true do
    local line = f.readLine()
    if line then
        table.insert(patch_lines, line)
    else
        break
    end
    if (os.clock() - last_pause) >= 2.8 then
        os.queueEvent("")
        os.pullEvent("")
        last_pause = os.clock()
    end
end
f.close()
local line_offset = 0

for i=1, #patch_lines do
    local line_new, type, text = string.match(patch_lines[i], "(%d+)([%>%<])([^%>%<]*)")
    line_new = tonumber(line_new)
    --print(type)
    if type == ">" then
        --print("ADD LINE "..line_new..": \""..text.."\"")
        table.insert(lines, line_new, text)
    elseif type == "<" then
        local start_search = line_new-5
        local pos = line_new
        if start_search < 1 then
            start_search = 1
        end
        for j=start_search, line_new+5 do
            if lines[j] == text then
                pos = j
                break
            end
        end
        --print("REMOVE LINE "..pos.."("..line_new..")"..": \""..lines[pos].."\"")
        table.remove(lines, pos)
    end
end

local f = fs.open(args[1]..".out", "w")
for i=1, #lines do
    f.writeLine(lines[i])
end
f.close()