--:Minify:--
local kernel = ...

local bit32 = require("bit32")
local bor = bit32.bor
local lshift = bit32.lshift

--   bit 0 = everyone-write,  bit 1 = everyone-read
--   bit 2 = group-write,     bit 3 = group-read
--   bit 4 = owner-write,     bit 5 = owner-read
--   bit 6 = suid
local P_OWNER_R = lshift(1, 5)
local P_OWNER_W = lshift(1, 4)
local P_GROUP_R = lshift(1, 3)
local P_GROUP_W = lshift(1, 2)
local P_WORLD_R = lshift(1, 1)
local P_WORLD_W = lshift(1, 0)
local P_SUID    = lshift(1, 6)

local RW_R_R   = bor(P_OWNER_R, P_OWNER_W, P_GROUP_R, P_WORLD_R)         -- 644 / rw-r--r--
local RWX_R_R  = bor(P_OWNER_R, P_OWNER_W, P_GROUP_R, P_WORLD_R)         -- 755 / rwxr--r--
local RW_R__   = bor(P_OWNER_R, P_OWNER_W, P_GROUP_R)                    -- 640 / rw-r-----
local RW____   = bor(P_OWNER_R, P_OWNER_W)                               -- 600 / rw-------
local SUID_755 = bor(P_SUID, P_OWNER_R, P_OWNER_W, P_GROUP_R, P_WORLD_R) -- 4755

local function metaEntry(name, owner, group, perms)
    return string.char(#name) .. name
        .. string.char(owner, group, perms)
        .. string.char(0)
end

local rootDisk = kernel.disks["$"]

local function writeMeta(dir, entries)
    local diskDir = dir == "/" and "/" or dir
    local path = (diskDir:sub(-1) == "/" and diskDir or diskDir .. "/") .. ".meta"
    if path:sub(1,1) == "/" then path = path:sub(2) end
    if path == "" then path = ".meta" end

    local data = ""
    for _, e in ipairs(entries) do
        data = data .. metaEntry(e[1], e[2], e[3], e[4])
    end

    local ok, err = pcall(function()
        local f = rootDisk:open(path, "w")
        f.write(data)
        f.close()
    end)
    if not ok then
        kernel.log("permissions: failed to write /" .. path .. ": " .. tostring(err), "WARN", 8)
    end
end

if rootDisk:fileExists(".meta") then
    kernel.log("Permissions already seeded, skipping.", "INFO")
else
    kernel.log("Seeding filesystem permissions...", "INFO")

    writeMeta("/", {
        {"bin",     0, 0, RWX_R_R},
        {"boot",    0, 0, RWX_R_R},
        {"dev",     0, 0, RWX_R_R},
        {"etc",     0, 0, RWX_R_R},
        {"home",    0, 0, RWX_R_R},
        {"lib",     0, 0, RWX_R_R},
        {"root",    0, 0, RW____  },
        {"sbin",    0, 0, RWX_R_R},
        {"tmp",     0, 0, bor(P_OWNER_R, P_OWNER_W, P_GROUP_R, P_GROUP_W, P_WORLD_R, P_WORLD_W)},
        {"usr",     0, 0, RWX_R_R},
        {"var",     0, 0, RWX_R_R},
    })

    writeMeta("/bin", {
        {"cat",     0, 0, RWX_R_R},
        {"clear",   0, 0, RWX_R_R},
        {"echo",    0, 0, RWX_R_R},
        {"hfetch",  0, 0, RWX_R_R},
        {"hysh",    0, 0, RWX_R_R},
        {"hyshex",  0, 0, RWX_R_R},
        {"install", 0, 0, RWX_R_R},
        {"login",   0, 0, SUID_755},
        {"ls",      0, 0, RWX_R_R},
        {"lua",     0, 0, RWX_R_R},
        {"luaold",  0, 0, RWX_R_R},
        {"mkdir",   0, 0, RWX_R_R},
        {"ps",      0, 0, RWX_R_R},
        {"pwd",     0, 0, RWX_R_R},
        {"spm",     0, 0, RWX_R_R},
        {"su",      0, 0, SUID_755},
        {"sudo",    0, 0, SUID_755},
        {"sysdump", 0, 0, RWX_R_R},
        {"whoami",  0, 0, RWX_R_R},
        {"yes",     0, 0, RWX_R_R},
        {"startup", 0, 0, RWX_R_R},
    })

    writeMeta("/bin/startup", {
        {"test.lua",    0, 0, RWX_R_R},
    })

    writeMeta("/etc", {
        {"passwd",  0, 0, RW_R_R},
        {"shadow",  0, 0, RW____  },
        {"pam.d",   0, 0, RWX_R_R},
    })

    writeMeta("/etc/pam.d", {
        {"secret",  0, 0, RW____},
    })

    writeMeta("/sbin", {
        {"init.lua", 0, 0, RWX_R_R},
    })

    writeMeta("/boot", {
        {"kernel.lua",   0, 0, RW_R_R},
        {"boot.cfg",     0, 0, RW_R_R},
        {"safeboot.cfg", 0, 0, RW_R_R},
        {"fstab",        0, 0, RW_R_R},
        {"initfs",       0, 0, RW_R_R},
        {"cct",          0, 0, RWX_R_R},
        {"oc",           0, 0, RWX_R_R},
    })

    writeMeta("/lib", {
        {"sys",     0, 0, RWX_R_R},
        {"modules", 0, 0, RWX_R_R},
        {"crypto",  0, 0, RWX_R_R},
        {"store",   0, 0, RWX_R_R},
        {"snip",    0, 0, RW_R_R},
        {"io",      0, 0, RW_R_R},
        {"bit32",   0, 0, RW_R_R},
    })

    kernel.log("Filesystem permissions seeded.", "INFO")
end

-- TODO: move this to vfs.kmod
local _orig_open = kernel.vfs.open
kernel.vfs.open = function(path, mode)
    local fd = _orig_open(path, mode)
    if mode == "r" then
        local task = kernel.currentTask
        local fobj = task.fd[fd]
        if fobj and fobj.meta then
            local suid_set = bit32.extract(fobj.meta.perms, 6) == 1
            if suid_set then
                fobj.suid_owner = fobj.meta.owner
            end
        end
    end
    return fd
end

kernel.syscalls["fget_suid"] = function(fd)
    local task = kernel.currentTask
    local fobj = task and task.fd[fd]
    if fobj and fobj.suid_owner then
        return fobj.suid_owner
    end
    return nil
end

kernel.log("Permission module loaded.", "INFO")