---@diagnostic disable: unused-local
local file=assert(io.open('/home/user/.local/state/nvim/undo/%home%user%.config%nvim%init.lua'))
local function get(n)
    return file:read(n)
end
local function nget(n)
    --NOTE: this will always return a signed integer,
    --      while the actual implementation may return an unsigned integer
    local ret=0
    for i in get(n):gmatch'.' do
        ret=ret*256+string.byte(i)
    end
    return ret
end
--Header
assert(get(9)=='Vim\x9fUnDo\xe5')
local version=nget(2)
assert(version==3)
local hash=get(32)
local line_count=nget(4)
-- "U" command data
local str_len=nget(4)
local line_ptr=get(str_len)
local U_lnum=nget(4)
local U_colnr=nget(4)
-- Header
local old_header_seq=nget(4)
local new_header_seq=nget(4)
local cur_header_seq=nget(4)
local num_head=nget(4)
local seq_last=nget(4)
local seq_cur=get(4)
local seq_time=nget(8)
local last_save_nr=0
while true do
    local len=nget(1)
    if len==0 then break end
    local what=nget(1)
    if what==1 then
        assert(len==4)
        last_save_nr=nget(4)
    else
        -- Field not supported, read and discard
        for _=1,len do get(1) end
    end
end
local function unserialize()
    local function pos_read(t)
        t.pos_lnum=nget(4)
        t.pos_col=nget(4)
        t.pos_coladd=nget(4)
    end
    local uhp={}
    uhp.next_seq=nget(4)
    uhp.prev_seq=nget(4)
    uhp.alt_next_seq=nget(4)
    uhp.alt_prev_seq=nget(4)
    uhp.seq=nget(4)
    pos_read(uhp)
    uhp.cursor_vcol=nget(4)
    uhp.flags=nget(2)
    uhp.marks=vim.defaulttable(function () return {} end)
    local time=os.time()
    for i=1,26 do
        pos_read(uhp.marks[i])
        uhp.marks[i].timestamp=time
        uhp.marks[i].fnum=0
    end
    uhp.vi_start={}
    pos_read(uhp.vi_start)
    uhp.vi_end={}
    pos_read(uhp.vi_end)
    uhp.vi_mode=nget(4)
    uhp.vi_curswant=nget(4)
    uhp.time=nget(8)
    while true do
        local len=nget(1)
        if len==0 then break end
        local what=nget(1)
        if what==1 then
            assert(len==4)
            uhp.save_nr=nget(4)
        else
            -- Field not supported, read and discard
            for _=1,len do get(1) end
        end
    end
    local last_uep
    local m
    while true do
        m=get(2)
        if m~='\xf5\x18' then break end
        local uep={}
        uep.top=nget(4)
        uep.bot=nget(4)
        uep.lcount=nget(4)
        uep.size=nget(4)
        uep.array={}
        for i=1,uep.size do
            local line_len=nget(4)
            local line=get(line_len)
            uep.array[i]=line
        end
        if not last_uep then
            uhp.entry=uep
        else
            last_uep.next=uep
        end
        last_uep=uep
    end
    assert(m=='\x35\x81')
    while true do
        m=get(2)
        if m~='\xf5\x18' then break end
        local ext={}
        local type=nget(4)
        ext.type=type
        if type==0 then
            ext.raw_data=get(48)
        elseif type==1 then
            ext.raw_data=get(48)
        else error'' end
    end
    assert(m=='\x35\x81')
    return uhp
end
local uhps={}
local m
while true do
    m=get(2)
    if m~='\x5f\xd0' then break end
    table.insert(uhps,unserialize())
end
assert(#uhps==num_head)
assert(m=='\xe7\xaa')