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local paths = require("Paths")
local event = require("Event")

--------------------------------------------------------------------------------

local filesystem = {
    SORTING_NAME = 1,
    SORTING_TYPE = 2,
    SORTING_DATE = 3,
}

local BUFFER_SIZE = 1024
local BOOT_PROXY

local mountedProxies = {}

--------------------------------------- String-related path processing -----------------------------------------

function filesystem.path(path)
    return path:match("^(.+%/).") or ""
end

function filesystem.name(path)
    return path:match("%/?([^%/]+%/?)$")
end

function filesystem.extension(path, lower)
    return path:match("[^%/]+(%.[^%/]+)%/?$")
end

function filesystem.hideExtension(path)
    return path:match("(.+)%..+") or path
end

function filesystem.isHidden(path)
    if path:sub(1, 1) == "." then
        return true
    end

    return false
end

function filesystem.removeSlashes(path)
    return path:gsub("/+", "/")
end

--------------------------------------- Mounted filesystem support -----------------------------------------

function filesystem.mount(cyka, path)
    if type(cyka) == "table" then
        for i = 1, #mountedProxies do
            if mountedProxies[i].path == path then
                return false, "mount path has been taken by other mounted filesystem"
            elseif mountedProxies[i].proxy == cyka then
                return false, "proxy is already mounted"
            end
        end

        table.insert(mountedProxies, {
            path = path,
            proxy = cyka
        })

        return true
    else
        error("bad argument #1 (filesystem proxy expected, got " .. tostring(cyka) .. ")")
    end
end

function filesystem.unmount(cyka)
    if type(cyka) == "table" then
        for i = 1, #mountedProxies do
            if mountedProxies[i].proxy == cyka then
                table.remove(mountedProxies, i)
                return true
            end
        end

        return false, "specified proxy is not mounted"
    elseif type(cyka) == "string" then
        for i = 1, #mountedProxies do
            if mountedProxies[i].proxy.address == cyka then
                table.remove(mountedProxies, i)
                return true
            end
        end

        return false, "specified proxy address is not mounted"
    else
        error("bad argument #1 (filesystem proxy or mounted path expected, got " .. tostring(cyka) .. ")")
    end
end

function filesystem.get(path)
    checkArg(1, path, "string")

    for i = 1, #mountedProxies do
        if path:sub(1, unicode.len(mountedProxies[i].path)) == mountedProxies[i].path then
            return mountedProxies[i].proxy, unicode.sub(path, mountedProxies[i].path:len() + 1, -1)
        end
    end

    return BOOT_PROXY, path
end

function filesystem.mounts()
    local key, value
    return function()
        key, value = next(mountedProxies, key)
        if value then
            return value.proxy, value.path
        end
    end
end

--------------------------------------- I/O methods -----------------------------------------

local function readString(self, count)
    -- If current buffer content is a "part" of "count of data" we need to read
    if count > #self.buffer then
        local data, chunk = self.buffer

        while #data < count do
            chunk = self.proxy.read(self.stream, BUFFER_SIZE)

            if chunk then
                data = data .. chunk
            else
                self.position = self:seek("end", 0)

                -- EOF at start
                if data == "" then
                    return nil
                -- EOF after read
                else
                    return data
                end
            end
        end

        self.buffer = data:sub(count + 1, -1)
        chunk = data:sub(1, count)
        self.position = self.position + #chunk

        return chunk
    else
        local data = self.buffer:sub(1, count)
        self.buffer = self.buffer:sub(count + 1, -1)
        self.position = self.position + count

        return data
    end
end

local function readLine(self)
    local data = ""
    while true do
        if #self.buffer > 0 then
            local starting, ending = self.buffer:find("\n")
            if starting then
                local chunk = self.buffer:sub(1, starting - 1)
                self.buffer = self.buffer:sub(ending + 1, -1)
                self.position = self.position + #chunk

                return data .. chunk
            else
                data = data .. self.buffer
            end
        end

        local chunk = self.proxy.read(self.stream, BUFFER_SIZE)
        if chunk then
            self.buffer = chunk
            self.position = self.position + #chunk
        -- EOF
        else
            local data = self.buffer
            self.position = self:seek("end", 0)

            return #data > 0 and data or nil
        end
    end
end

local function lines(self)
    return function()
        local line = readLine(self)
        if line then
            return line
        else
            self:close()
        end
    end
end

local function readAll(self)
    local data, chunk = ""
    while true do
        chunk = self.proxy.read(self.stream, 4096)
        if chunk then
            data = data .. chunk
        -- EOF
        else
            self.position = self:seek("end", 0)
            return data
        end
    end
end

local function readBytes(self, count, littleEndian)
    if count == 1 then
        local data = readString(self, 1)
        if data then
            return string.byte(data)
        end

        return nil
    else
        local bytes, result = {string.byte(readString(self, count) or "\x00", 1, 8)}, 0

        if littleEndian then
            for i = #bytes, 1, -1 do
                result = bit32.bor(bit32.lshift(result, 8), bytes[i])
            end
        else
            for i = 1, #bytes do
                result = bit32.bor(bit32.lshift(result, 8), bytes[i])
            end
        end

        return result
    end
end

local function readUnicodeChar(self)
    local byteArray = {string.byte(readString(self, 1))}

    local nullBitPosition = 0
    for i = 1, 7 do
        if bit32.band(bit32.rshift(byteArray[1], 8 - i), 0x1) == 0x0 then
            nullBitPosition = i
            break
        end
    end

    for i = 1, nullBitPosition - 2 do
        table.insert(byteArray, string.byte(readString(self, 1)))
    end

    return string.char(table.unpack(byteArray))
end

local function read(self, format, ...)
    local formatType = type(format)
    if formatType == "number" then
        return readString(self, format)
    elseif formatType == "string" then
        format = format:gsub("^%*", "")

        if format == "a" then
            return readAll(self)
        elseif format == "l" then
            return readLine(self)
        elseif format == "b" then
            return readBytes(self, 1)
        elseif format == "bs" then
            return readBytes(self, ...)
        elseif format == "u" then
            return readUnicodeChar(self)
        else
            error("bad argument #2 ('a' (whole file), 'l' (line), 'u' (unicode char), 'b' (byte as number) or 'bs' (sequence of n bytes as number) expected, got " .. format .. ")")
        end
    else
        error("bad argument #1 (number or string expected, got " .. formatType ..")")
    end
end

local function seek(self, pizda, cyka)
    if pizda == "set" then
        local result, reason = self.proxy.seek(self.stream, "set", cyka)
        if result then
            self.position = result
            self.buffer = ""
        end

        return result, reason
    elseif pizda == "cur" then
        local result, reason = self.proxy.seek(self.stream, "set", self.position + cyka)
        if result then
            self.position = result
            self.buffer = ""
        end

        return result, reason
    elseif pizda == "end" then
        local result, reason = self.proxy.seek(self.stream, "end", cyka)
        if result then
            self.position = result
            self.buffer = ""
        end

        return result, reason
    else
        error("bad argument #2 ('set', 'cur' or 'end' expected, got " .. tostring(whence) .. ")")
    end
end

local function write(self, ...)
    local data = {...}
    for i = 1, #data do
        data[i] = tostring(data[i])
    end
    data = table.concat(data)

    -- Data is small enough to fit buffer
    if #data < (BUFFER_SIZE - #self.buffer) then
        self.buffer = self.buffer .. data

        return true
    else
        -- Write current buffer content
        local success, reason = self.proxy.write(self.stream, self.buffer)
        if success then
            -- If data will not fit buffer, use iterative writing with data partitioning
            if #data > BUFFER_SIZE then
                for i = 1, #data, BUFFER_SIZE do
                    success, reason = self.proxy.write(self.stream, data:sub(i, i + BUFFER_SIZE - 1))

                    if not success then
                        break
                    end
                end

                self.buffer = ""

                return success, reason
            -- Data will perfectly fit in empty buffer
            else
                self.buffer = data

                return true
            end
        else
            return false, reason
        end
    end
end

local function writeBytes(self, ...)
    return write(self, string.char(...))
end

local function close(self)
    if self.write and #self.buffer > 0 then
        self.proxy.write(self.stream, self.buffer)
    end

    return self.proxy.close(self.stream)
end

function filesystem.open(path, mode)
    local proxy, proxyPath = filesystem.get(path)
    local result, reason = proxy.open(proxyPath, mode)
    if result then
        local handle = {
            proxy = proxy,
            stream = result,
            position = 0,
            buffer = "",
            close = close,
            seek = seek,
        }

        if mode == "r" or mode == "rb" then
            handle.readString = readString
            handle.readUnicodeChar = readUnicodeChar
            handle.readBytes = readBytes
            handle.readLine = readLine
            handle.lines = lines
            handle.readAll = readAll
            handle.read = read

            return handle
        elseif mode == "w" or mode == "wb" or mode == "a" or mode == "ab" then
            handle.write = write
            handle.writeBytes = writeBytes

            return handle
        else
            error("bad argument #2 ('r', 'rb', 'w', 'wb' or 'a' expected, got )" .. tostring(mode) .. ")")
        end
    else
        return nil, reason
    end
end

--------------------------------------- Rest proxy methods -----------------------------------------

function filesystem.exists(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.exists(proxyPath)
end

function filesystem.size(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.size(proxyPath)
end

function filesystem.isDirectory(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.isDirectory(proxyPath)
end

function filesystem.makeDirectory(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.makeDirectory(proxyPath)
end

function filesystem.lastModified(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.lastModified(proxyPath)
end

function filesystem.remove(path)
    local proxy, proxyPath = filesystem.get(path)
    return proxy.remove(proxyPath)
end

function filesystem.list(path, sortingMethod)
    local proxy, proxyPath = filesystem.get(path)

    local list, reason = proxy.list(proxyPath)
    if list then
        -- Fullfill list with mounted paths if needed
        for i = 1, #mountedProxies do
            if path == filesystem.path(mountedProxies[i].path) then
                table.insert(list, filesystem.name(mountedProxies[i].path))
            end
        end

        -- Applying sorting methods
        if not sortingMethod or sortingMethod == filesystem.SORTING_NAME then
            table.sort(list, function(a, b)
                return unicode.lower(a) < unicode.lower(b)
            end)

            return list
        elseif sortingMethod == filesystem.SORTING_DATE then
            table.sort(list, function(a, b)
                return filesystem.lastModified(path .. a) > filesystem.lastModified(path .. b)
            end)

            return list
        elseif sortingMethod == filesystem.SORTING_TYPE then
            -- Creating a map with "extension" = {file1, file2, ...} structure
            local map, extension = {}
            for i = 1, #list do
                extension = filesystem.extension(list[i]) or "Z"

                -- If it's a directory without extension
                if extension:sub(1, 1) ~= "." and filesystem.isDirectory(path .. list[i]) then
                    extension = "."
                end

                map[extension] = map[extension] or {}
                table.insert(map[extension], list[i])
            end

            -- Sorting lists for each extension
            local extensions = {}
            for key, value in pairs(map) do
                table.sort(value, function(a, b)
                    return unicode.lower(a) < unicode.lower(b)
                end)

                table.insert(extensions, key)
            end

            -- Sorting extensions
            table.sort(extensions, function(a, b)
                return unicode.lower(a) < unicode.lower(b)
            end)

            -- Fullfilling final list
            list = {}
            for i = 1, #extensions do
                for j = 1, #map[extensions[i]] do
                    table.insert(list, map[extensions[i]][j])
                end
            end

            return list
        end
    end

    return list, reason
end

function filesystem.rename(fromPath, toPath)
    local fromProxy, fromProxyPath = filesystem.get(fromPath)
    local toProxy, toProxyPath = filesystem.get(toPath)

    -- If it's the same filesystem component
    if fromProxy.address == toProxy.address then
        return fromProxy.rename(fromProxyPath, toProxyPath)
    else
        -- Copy files to destination
        filesystem.copy(fromPath, toPath)
        -- Remove original files
        filesystem.remove(fromPath)
    end
end

--------------------------------------- Advanced methods -----------------------------------------

function filesystem.copy(fromPath, toPath)
    local function copyRecursively(fromPath, toPath)
        if filesystem.isDirectory(fromPath) then
            filesystem.makeDirectory(toPath)

            local list = filesystem.list(fromPath)
            for i = 1, #list do
                copyRecursively(fromPath .. "/" .. list[i], toPath .. "/" .. list[i])
            end
        else
            local fromHandle = filesystem.open(fromPath, "rb")
            if fromHandle then
                local toHandle = filesystem.open(toPath, "wb")
                if toHandle then
                    while true do
                        local chunk = readString(fromHandle, BUFFER_SIZE)
                        if chunk then
                            if not write(toHandle, chunk) then
                                break
                            end
                        else
                            toHandle:close()
                            fromHandle:close()

                            break
                        end
                    end
                end
            end
        end
    end

    copyRecursively(fromPath, toPath)
end

function filesystem.read(path)
    local handle, reason = filesystem.open(path, "rb")
    if handle then
        local data = readAll(handle)
        handle:close()

        return data
    end

    return false, reason
end

function filesystem.lines(path)
    local handle, reason = filesystem.open(path, "rb")
    if handle then
        return handle:lines()
    else
        error(reason)
    end
end

function filesystem.readLines(path)
    local handle, reason = filesystem.open(path, "rb")
    if handle then
        local lines, index, line = {}, 1

        repeat
            line = readLine(handle)
            lines[index] = line
            index = index + 1
        until not line

        handle:close()

        return lines
    end

    return false, reason
end

local function writeOrAppend(append, path, ...)
    filesystem.makeDirectory(filesystem.path(path))

    local handle, reason = filesystem.open(path, append and "ab" or "wb")
    if handle then
        local result, reason = write(handle, ...)
        handle:close()

        return result, reason
    end

    return false, reason
end

function filesystem.write(path, ...)
    return writeOrAppend(false, path,...)
end

function filesystem.append(path, ...)
    return writeOrAppend(true, path, ...)
end

function filesystem.writeTable(path, ...)
    return filesystem.write(path, require("Text").serialize(...))
end

function filesystem.readTable(path)
    local result, reason = filesystem.read(path)
    if result then
        return require("Text").deserialize(result)
    end

    return result, reason
end

function filesystem.setProxy(proxy)
    BOOT_PROXY = proxy
end

function filesystem.getProxy()
    return BOOT_PROXY
end

--------------------------------------- loadfile() and dofile() implementation -----------------------------------------

function loadfile(path)
    local data, reason = filesystem.read(path)
    if data then
        return load(data, "=" .. path)
    end

    return nil, reason
end

function dofile(path, ...)
    local result, reason = loadfile(path)
    if result then
        local data = {xpcall(result, debug.traceback, ...)}
        if data[1] then
            return table.unpack(data, 2)
        else
            error(data[2])
        end
    else
        error(reason)
    end
end

--------------------------------------------------------------------------------

-- Mount all existing filesystem components
for address in component.list("filesystem") do
    filesystem.mount(component.proxy(address), paths.system.mounts .. address .. "/")
end

-- Automatically mount/unmount filesystem components
event.addHandler(function(signal, address, type)
    if signal == "component_added" and type == "filesystem" then
        filesystem.mount(component.proxy(address), paths.system.mounts .. address .. "/")
    elseif signal == "component_removed" and type == "filesystem" then
        filesystem.unmount(address)
    end
end)

--------------------------------------------------------------------------------

return filesystem