local kernel = ...
local openFiles = {}
kernel.openFiles = openFiles
local vfs = {}
vfs.mounts = {}
local disks = kernel.disks
vfs.cwd = ""

local function resolvePath(path)
    local mountPoint = "/"
    local mountId = "$"
    if path:sub(1,1)~="/" then path=vfs.cwd..path end
    for k,v in pairs(vfs.mounts) do
        if path:sub(1,#v) == v and #v > #mountPoint then
            mountPoint = v
            mountId = k
        end
    end
    local diskPath = path:sub(#mountPoint+1)
    return disks[mountId], diskPath
end

function vfs.mount(diskId, path)
    if kernel.uid ~= 0 then error("Permission denied") end
    if not disks[diskId] then
        error("Attempted to mount unknown disk '"..diskId.."'")
        return false
    end
    if vfs.mounts[diskId] then
        error("Disk '"..diskId.."' is already mounted")
        return false
    end
    if path:sub(#path,#path)~="/" then path=path.."/" end
    for i,v in pairs(vfs.mounts) do
        if v == path then
            error("Mount point '"..path.."' is already in use")
            return false
        end
    end
    vfs.mounts[diskId] = path
end

function vfs.unmount(path)
    if kernel.uid ~= 0 then error("Permission denied") end
    for k,v in pairs(vfs.mounts) do
        if v == path then
            vfs.mounts[k] = nil
            return true
        end
    end
    return false
end

function vfs.open(path, mode)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return nil
    end
    local uuid = kernel.newUUID()
    openFiles[uuid] = {disk=disk.address, path=path, mode=mode, handle=disk:open(diskPath, mode)}
    return uuid
end

function vfs.close(fileId)
    local file = openFiles[fileId]
    if not file then
        error("Invalid file handle")
        return false
    end
    local disk = disks[file.disk]
    disk:close(file.handle)
    openFiles[fileId] = nil
    return true
end

function vfs.read(fileId, count)
    local file = openFiles[fileId]
    if not file then
        error("Invalid file handle")
        return nil
    end
    if not file.mode:find("r") then
        error("File not opened in read mode")
        return nil
    end
    local disk = disks[file.disk]
    return disk:read(file.handle, count)
end

function vfs.write(fileId, data)
    local file = openFiles[fileId]
    if not file then
        error("Invalid file handle")
        return false
    end
    if not file.mode:find("w") then
        error("File not opened in write mode")
        return false
    end
    local disk = disks[file.disk]
    return disk:write(file.handle, data)
end

function vfs.mkdir(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return false
    end
    return disk:mkdir(diskPath)
end

function vfs.remove(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return false
    end
    return disk:remove(diskPath)
end

function vfs.atributes(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return nil
    end
    return disk:attributes(diskPath)
end

function vfs.list(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return nil
    end
    return disk:list(diskPath)
end

function vfs.exists(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return false
    end
    return disk:directoryExists(diskPath) or disk:fileExists(diskPath)
end

function vfs.type(path)
    local disk, diskPath = resolvePath(path)
    if not disk then
        error("No disk mounted for path '"..path.."'")
        return nil
    end
    return disk:type(diskPath)
end

function vfs.getcwd()
    return vfs.cwd
end

function vfs.setcwd(path)
    if path:sub(#path,#path)~="/" then path=path.."/" end
    if path:sub(1,1)~="/" then path="/"..path end
    vfs.cwd=path
end

kernel.vfs = vfs
kernel.registerSyscall(0x01, vfs.open)
kernel.registerSyscall(0x02, vfs.read)
kernel.registerSyscall(0x03, vfs.write)
kernel.registerSyscall(0x04, vfs.close)
kernel.registerSyscall(0x05, vfs.list)
kernel.registerSyscall(0x06, vfs.type)
kernel.registerSyscall(0x07, vfs.atributes)
kernel.registerSyscall(0x08, vfs.mkdir)
kernel.registerSyscall(0x09, vfs.remove)
kernel.registerSyscall(0x0a, vfs.exists)
kernel.registerSyscall(0x0b, vfs.mount)
kernel.registerSyscall(0x0c, vfs.unmount)
kernel.registerSyscall(0x0d, vfs.getcwd)
kernel.registerSyscall(0x0e, vfs.setcwd)

kernel.log("VFS module loaded")