local args = {...}
local kernel = args[1]
local fs = {}
local disks = {}
local mounts = {["/"]="$"}

-- path normaliing
local function normalizePath(path)
    if not path or path == "" then return "/" end
    if path:sub(1,1) ~= "/" then path = "/" .. path end
    local parts = {}
    for part in path:gmatch("[^/]+") do
        if part == ".." then
            if #parts > 0 then table.remove(parts) end
        elseif part ~= "." and part ~= "" then
            parts[#parts+1] = part
        end
    end
    return "/" .. table.concat(parts, "/")
end

-- disk resolution
local function resolvePath(path)
    local abs = normalizePath(path)
    local best = "/"
    for mount, diskAddr in pairs(mounts) do
        if abs:sub(1, #mount) == mount and #mount > #best then
            best = mount
        end
    end
    local newPath = abs:sub(#best + 1)
    if newPath == "" then newPath = "/" end
    return disks[mounts[best]], newPath
end

-- Symlinks
-- Format: #!@SYMLINK[target]
local SYMLINK_PREFIX = "#!@SYMLINK["
local SYMLINK_SUFFIX = "]"
local SYMLINK_MAX_DEPTH = 64

local function isSymlink(disk, path)
    if not disk:fileExists(path) then return false end
    local text = disk:readAllText(path)
    if not text then return false end
    return text:sub(1, #SYMLINK_PREFIX) == SYMLINK_PREFIX
end

local function readSymlink(disk, path)
    local text = disk:readAllText(path)
    if not text then return nil end
    if text:sub(1, #SYMLINK_PREFIX) ~= SYMLINK_PREFIX then return nil end
    local target = text:sub(#SYMLINK_PREFIX + 1)
    if target:sub(-1) == SYMLINK_SUFFIX then
        target = target:sub(1, -2)
    end
    return target
end


-- Path resolution
local function splitPath(p)
    local parts = {}
    for part in p:gmatch("[^/]+") do parts[#parts+1] = part end
    return parts
end

local function resolveSymlink(path)
    path = normalizePath(path)
    local symlinkDepth = 0
    local parts = splitPath(path)
    local resolved = {}
    local i = 1

    while i <= #parts do
        local comp = parts[i]
        if comp == "." then
        elseif comp == ".." then
            if #resolved > 0 then table.remove(resolved) end
        else
            local currentPath = "/" .. table.concat(resolved, "/")
            local disk, p = resolvePath(currentPath .. "/" .. comp)
            if isSymlink(disk, p) then
                symlinkDepth = symlinkDepth + 1
                if symlinkDepth > SYMLINK_MAX_DEPTH then
                    error("Too many levels of symbolic links: " .. path)
                end
                local target = readSymlink(disk, p)
                if not target then
                    resolved[#resolved+1] = comp
                else
                    if target:sub(1,1) == "/" then
                        resolved = splitPath(normalizePath(target))
                    else
                        local base = resolved
                        resolved = {}
                        for _, seg in ipairs(base) do resolved[#resolved+1]=seg end
                        for seg in target:gmatch("[^/]+") do
                            if seg == ".." then
                                if #resolved>0 then table.remove(resolved) end
                            elseif seg ~= "." then
                                resolved[#resolved+1]=seg
                            end
                        end
                    end
                    local remaining = {}
                    for j=i+1,#parts do remaining[#remaining+1]=parts[j] end
                    parts = remaining
                    i = 0
                end
            else
                resolved[#resolved+1]=comp
            end
        end
        i=i+1
    end

    local finalPath="/"..table.concat(resolved,"/")
    local disk,diskPath=resolvePath(finalPath)
    return disk,diskPath
end

-- PUBLIC API: MOUNTING
function fs.mount(disk, mountPoint)
    if kernel.uid ~= 0 then error("Permission Denied") end
    mounts[mountPoint]=disk
end
function fs.unmount(mountPoint)
    if kernel.uid ~= 0 then error("Permission Denied") end
    mounts[mountPoint]=nil
end
function fs.virtDisk(diskObj)
    if kernel.uid ~= 0 then error("Permission Denied") end
    if disks[diskObj.address] then error("Disk exists") end
    disks[diskObj.address]=diskObj
end
function fs.eject(addr)
    if kernel.uid ~= 0 then error("Permission Denied") end
    disks[addr]=nil
end

-- SYMLINK API
function fs.symlink(target, linkPath)
    local disk, p = resolvePath(linkPath)
    return disk:writeAllText(p, SYMLINK_PREFIX..target..SYMLINK_SUFFIX)
end
function fs.isLink(path)
    local disk, p = resolvePath(path)
    return isSymlink(disk,p)
end
function fs.readLink(path)
    local disk, p = resolvePath(path)
    return readSymlink(disk,p)
end

-- FILE OPERATIONS
function fs.exists(path)
    local disk, p = resolveSymlink(path)
    return disk:fileExists(p) or disk:directoryExists(p)
end

function fs.isFile(path)
    local disk, p = resolveSymlink(path)
    if isSymlink(disk, p) then return false end
    return disk:fileExists(p)
end

function fs.isDir(path)
    local disk, p = resolveSymlink(path)
    if isSymlink(disk, p) then return false end
    return disk:directoryExists(p)
end

function fs.list(path)
    local disk, p = resolveSymlink(path)
    return disk:list(p)
end

function fs.makeDir(path)
    local disk, p = resolveSymlink(path)
    return disk:makeDirectory(p)
end

function fs.remove(path)
    local disk, p = resolvePath(path)
    if isSymlink(disk, p) then
        return disk:remove(p)
    end
    local d2, p2 = resolveSymlink(path)
    return d2:remove(p2)
end

function fs.readAllText(path)
    local disk, p = resolveSymlink(path)
    return disk:readAllText(p)
end

function fs.writeAllText(path, text)
    local disk, p = resolveSymlink(path)
    return disk:writeAllText(p, text)
end

function fs.appendAllText(path, text)
    local disk, p = resolveSymlink(path)
    return disk:appendAllText(p, text)
end

function fs.getSize(path)
    local disk, p = resolveSymlink(path)
    return disk:getSize(p)
end

-- INIT
for _,v in kernel.initdisks.list() do fs.virtDisk(v) end
kernel.fs=fs
kernel.chache.preload.fs=fs
kernel.chache.preload.filesystem=fs