-- DESCRIPTION: Install apps from public Xteink repositories

local ROOT = "/.apps/AppStore"
local REPOSITORIES_PATH = ROOT .. "/repositories.txt"
local DEFAULT_REPOSITORIES_PATH = ROOT .. "/repositories.default.txt"
local MAX_CATALOG_BYTES = 32768
local MAX_MANIFEST_BYTES = 16384
local MAX_APP_BYTES = 16 * 1024 * 1024
local MAX_FILE_BYTES = 8 * 1024 * 1024
local MAX_FILES = 64

local screen = "repositories"
local repositories = {}
local apps = {}
local selected = 1
local message = ""
local pendingRepository = nil
local pendingApp = nil
local needsDraw = true
local lastScreen = nil

local function removeFile(path)
    if fs.exists(path) then fs.remove(path) end
end

local function clearTree(path)
    if not fs.exists(path) then return true end
    local ok, err = fs.removeTree(path)
    if not ok or fs.exists(path) then return nil, err or "Could not remove " .. path end
    return true
end

local function validRelativePath(path)
    if not path or path == "" or path:sub(1, 1) == "/" or path:find("\\", 1, true) then return false end
    if not path:match("^[%w%._/%-]+$") then return false end
    for component in path:gmatch("[^/]+") do
        if component == "." or component == ".." then return false end
    end
    return not path:find("//", 1, true) and path:sub(-1) ~= "/"
end

local function validHash(value)
    return value and #value == 64 and value:match("^[0-9a-fA-F]+$") ~= nil
end

-- Version Marker - the catalog carries no version field, so the manifest hash stands
-- in for one. An installed tree with no marker predates this and counts as stale.
local function installState(id, manifestHash)
    local target = "/.apps/" .. id
    if not fs.exists(target) then return "none" end
    return fs.readFile(target .. "/.manifest.hash") == manifestHash and "current" or "update"
end

local function readLines(path, expectedHeader, onLine)
    local offset = 0
    local first = true
    while true do
        local line, nextOffset = fs.readLineAt(path, offset)
        if not line then
            if nextOffset then return nil, "Line exceeds 192 bytes" end
            break
        end
        offset = nextOffset
        if first then
            first = false
            if line ~= expectedHeader then return nil, "Unsupported format" end
        elseif line ~= "" and line:sub(1, 1) ~= "#" then
            local ok, err = onLine(line)
            if not ok then return nil, err end
        end
    end
    if first then return nil, "Empty file" end
    return true
end

local function loadRepositories()
    if not fs.exists(REPOSITORIES_PATH) then
        local defaults = fs.readFile(DEFAULT_REPOSITORIES_PATH)
        if not defaults or not fs.writeFile(REPOSITORIES_PATH, defaults) then
            return nil, "Missing repositories.txt"
        end
    end

    local result = {}
    local ok, err = readLines(REPOSITORIES_PATH, "XTEINK-REPOSITORIES|1", function(line)
        local name, url = line:match("^([^|]+)|(https://[^/|]+/[^|]+)$")
        if not name or #name > 48 or #url > 160 or url:find("[?#]") then
            return nil, "Invalid repository entry"
        end
        if #result >= 8 then return nil, "Too many repositories" end
        result[#result + 1] = {
            name = name,
            url = url,
            downloadPath = ROOT .. "/.catalog-" .. (#result + 1) .. ".txt"
        }
        return true
    end)
    if not ok then return nil, err end
    if #result == 0 then return nil, "No repositories configured" end
    repositories = result
    return true
end

local function renderStatus(text)
    gui.clear()
    gui.drawCenteredText(FONT_UI_12, math.floor(gui.height() / 2), text, COLOR_BLACK, STYLE_BOLD)
    gui.refresh(REFRESH_HALF)
    lastScreen = "status"
end

local function download(url, destination, maxBytes, expectedSize, hash)
    removeFile(destination)
    collectgarbage("collect")
    log.debug("APPSTORE DOWNLOAD " .. destination)
    return net.download(url, destination, {
        maxBytes = maxBytes,
        expectedSize = expectedSize,
        sha256 = hash
    })
end

local function parseCatalog(repository, path)
    local baseUrl = repository.url:match("^(.*)/[^/]+$")
    if not baseUrl then return nil, "Invalid catalog URL" end

    local result = {}
    local ok, err = readLines(path, "XTEINK-CATALOG|1", function(line)
        local id, description, manifestPath, sizeText, hash =
            line:match("^([%w_-]+)|([^|]+)|([^|]+)|(%d+)|([0-9a-fA-F]+)$")
        local size = tonumber(sizeText)
        if not id or #id > 48 or #description > 80 or not validRelativePath(manifestPath) or
            not size or size < 1 or size > MAX_MANIFEST_BYTES or not validHash(hash) then
            return nil, "Invalid catalog entry"
        end
        if #result >= 64 then return nil, "Too many apps" end
        result[#result + 1] = {
            id = id,
            description = description,
            manifestPath = manifestPath,
            manifestSize = size,
            manifestHash = hash:lower(),
            baseUrl = baseUrl,
            state = installState(id, hash:lower())
        }
        return true
    end)
    if not ok then return nil, err end
    if #result == 0 then return nil, "Repository has no apps" end
    apps = result
    log.info("APPSTORE CATALOG_READY " .. #apps)
    return true
end

local function loadCatalog(repository)
    apps = {}
    collectgarbage("collect")

    renderStatus("Downloading catalog...")
    removeFile(repository.downloadPath)
    local bytes, err = download(repository.url, repository.downloadPath, MAX_CATALOG_BYTES)
    if not bytes then return nil, err end

    local ok
    ok, err = parseCatalog(repository, repository.downloadPath)
    removeFile(repository.downloadPath)
    if not ok then return nil, err end
    return true
end

local function parseManifest(path)
    local files = {}
    local seenFiles = {}
    local seenDirectories = {}
    local total = 0
    local hasMain = false
    local ok, err = readLines(path, "XTEINK-MANIFEST|1", function(line)
        local relative, sizeText, hash = line:match("^([^|]+)|(%d+)|([0-9a-fA-F]+)$")
        local size = tonumber(sizeText)
        local lower = relative and relative:lower()
        if not validRelativePath(relative) or lower == ".manifest.txt" or not size or size < 1 or
            size > MAX_FILE_BYTES or not validHash(hash) or seenFiles[lower] or seenDirectories[lower] then
            return nil, "Invalid manifest entry"
        end
        local parent = ""
        for component in lower:gmatch("[^/]+") do
            if parent ~= "" then
                if seenFiles[parent] then return nil, "Manifest path collision" end
                seenDirectories[parent] = true
            end
            parent = parent == "" and component or parent .. "/" .. component
        end
        if #files >= MAX_FILES or total + size > MAX_APP_BYTES then return nil, "App is too large" end
        seenFiles[lower] = true
        total = total + size
        hasMain = hasMain or relative == "main.lua"
        files[#files + 1] = { path = relative, size = size, hash = hash:lower() }
        return true
    end)
    if not ok then return nil, err end
    if not hasMain then return nil, "Manifest has no main.lua" end
    return files
end

local function failInstall(stage, installError)
    log.error("APPSTORE INSTALL_FAILED " .. tostring(installError))
    local ok, cleanupError = clearTree(stage)
    if not ok then return nil, tostring(installError) .. "; cleanup failed: " .. tostring(cleanupError) end
    return nil, installError
end

local function install(app)
    log.info("APPSTORE INSTALL_START " .. app.id)
    local target = "/.apps/" .. app.id
    if app.state == "current" then return nil, app.id .. " is up to date" end

    local stage = "/.apps/.install-" .. app.id
    local ok, err = clearTree(stage)
    if not ok then return nil, err end
    ok, err = fs.mkdir(stage)
    if not ok then return nil, err end

    local manifestUrl = app.baseUrl .. "/" .. app.manifestPath
    local manifestBase = manifestUrl:match("^(.*)/[^/]+$")
    local manifestPath = stage .. "/.manifest.txt"
    renderStatus("Downloading " .. app.id .. " manifest...")
    local bytes
    bytes, err = download(manifestUrl, manifestPath, MAX_MANIFEST_BYTES, app.manifestSize, app.manifestHash)
    if not bytes then return failInstall(stage, err) end

    local files
    files, err = parseManifest(manifestPath)
    if not files then return failInstall(stage, err) end
    log.info("APPSTORE MANIFEST_READY " .. app.id .. " " .. #files)

    for index, file in ipairs(files) do
        local parent = file.path:match("^(.*)/[^/]+$")
        if parent then
            ok, err = fs.mkdir(stage .. "/" .. parent)
            if not ok then return failInstall(stage, err) end
        end
        renderStatus("Installing " .. app.id .. " " .. index .. "/" .. #files)
        bytes, err = download(manifestBase .. "/" .. file.path, stage .. "/" .. file.path,
            file.size, file.size, file.hash)
        if not bytes then return failInstall(stage, err) end
    end
    ok, err = fs.remove(manifestPath)
    if not ok then return failInstall(stage, err) end
    if not fs.writeFile(stage .. "/.manifest.hash", app.manifestHash) then
        return failInstall(stage, "Could not record app version")
    end

    -- Swap Via Backup - fs.rename refuses an existing destination, and clearing the old
    -- tree up front would lose the installed app if the rename then failed.
    local backup = "/.apps/.old-" .. app.id
    local replacing = fs.exists(target)
    if replacing then
        ok, err = clearTree(backup)
        if not ok then return failInstall(stage, err) end
        ok, err = fs.rename(target, backup)
        if not ok then return failInstall(stage, err) end
    end

    ok, err = fs.rename(stage, target)
    if not ok then
        if replacing then fs.rename(backup, target) end
        return failInstall(stage, err)
    end
    if replacing then clearTree(backup) end

    app.state = "current"
    log.info("APPSTORE INSTALL_DONE " .. app.id)
    return true, app.id .. (replacing and " updated" or " installed")
end

local function showMessage(text, returnScreen)
    log.info("APPSTORE MESSAGE " .. tostring(text))
    message = text
    screen = "message"
    pendingRepository = returnScreen
    needsDraw = true
end

-- Fast Waveform For Same-Screen Edits - FAST is a differential drive that needs a
-- trusted previous frame; only a wholesale content change needs HALF's ghost clear.
local function refreshMode()
    local mode = screen == lastScreen and REFRESH_FAST or REFRESH_HALF
    lastScreen = screen
    return mode
end

local function drawList(title, items, label, description, rightHint)
    gui.clear()
    gui.drawCenteredText(FONT_UI_12, 28, title, COLOR_BLACK, STYLE_BOLD)
    local visible = math.max(1, math.floor((gui.height() - 130) / 38))
    local first = math.max(1, math.min(selected - math.floor(visible / 2), #items - visible + 1))
    local last = math.min(#items, first + visible - 1)
    local y = 72
    for index = first, last do
        local prefix = index == selected and "> " or "  "
        gui.drawText(FONT_UI_12, 36, y, prefix .. label(items[index]), COLOR_BLACK,
            index == selected and STYLE_BOLD or STYLE_NORMAL)
        y = y + 38
    end
    if items[selected] and description then
        gui.drawCenteredText(FONT_UI_10, gui.height() - 82, description(items[selected]), COLOR_BLACK, STYLE_NORMAL)
    end
    gui.drawButtonHints("Back", "Select", "", rightHint or "")
    gui.refresh(refreshMode())
end

local APP_STATE_SUFFIX = { current = " (installed)", update = " (update)" }

local function render()
    if screen == "repositories" then
        drawList("Repositories", repositories, function(item) return item.name end)
    elseif screen == "apps" then
        drawList("Apps", apps, function(item) return item.id .. (APP_STATE_SUFFIX[item.state] or "") end,
            function(item) return item.description end)
    elseif screen == "connecting" then
        renderStatus("Connecting to Wi-Fi...")
    else
        gui.clear()
        gui.drawCenteredText(FONT_UI_12, math.floor(gui.height() / 2), message:sub(1, 100), COLOR_BLACK, STYLE_BOLD)
        gui.drawButtonHints("Back", "OK", "", "")
        gui.refresh(refreshMode())
    end
    needsDraw = false
end

local function moveSelection(delta, items)
    if #items == 0 then return end
    selected = ((selected - 1 + delta) % #items) + 1
    needsDraw = true
end

local function openRepository()
    pendingRepository = repositories[selected]
    net.wifiConnect()
    screen = "connecting"
    needsDraw = true
end

function init()
    local ok, err = loadRepositories()
    if not ok then
        showMessage(err, "exit")
        return
    end
    log.info("APPSTORE READY")
end

function draw()
    if screen == "connecting" then
        if input.wasPressed("back") then
            net.wifiDisconnect()
            local returnScreen = pendingApp and "apps" or "repositories"
            pendingRepository = nil
            pendingApp = nil
            if returnScreen == "repositories" then selected = 1 end
            screen = returnScreen
            needsDraw = true
        else
            local status = net.wifiStatus()
            if status == "connected" then
                log.info("APPSTORE WIFI_CONNECTED")
                if pendingApp then
                    local app = pendingApp
                    pendingApp = nil
                    local ok, result = install(app)
                    showMessage(result, "apps")
                else
                    local repository = pendingRepository
                    pendingRepository = nil
                    local ok, err = loadCatalog(repository)
                    if ok then
                        selected = 1
                        screen = "apps"
                        needsDraw = true
                    else
                        showMessage(err, "repositories")
                    end
                end
            elseif status == "failed" then
                log.error("APPSTORE WIFI_FAILED")
                net.wifiDisconnect()
                local returnScreen = pendingApp and "apps" or "repositories"
                pendingApp = nil
                showMessage("Wi-Fi connection failed", returnScreen)
            end
        end
    elseif input.wasPressed("up") then
        moveSelection(-1, screen == "apps" and apps or repositories)
    elseif input.wasPressed("down") then
        moveSelection(1, screen == "apps" and apps or repositories)
    elseif input.wasPressed("confirm") then
        if screen == "repositories" then
            openRepository()
        elseif screen == "apps" then
            if apps[selected].state == "current" then
                showMessage(apps[selected].id .. " is up to date", "apps")
            elseif net.wifiStatus() == "connected" then
                local ok, result = install(apps[selected])
                showMessage(result, "apps")
            else
                pendingApp = apps[selected]
                net.wifiConnect()
                screen = "connecting"
                needsDraw = true
            end
        elseif screen == "message" then
            if pendingRepository == "exit" then
                net.wifiDisconnect()
                sys.exit()
                return
            end
            screen = pendingRepository or "repositories"
            pendingRepository = nil
            needsDraw = true
        end
    elseif input.wasPressed("back") then
        if screen == "apps" then
            selected = 1
            screen = "repositories"
            needsDraw = true
        elseif screen == "message" and pendingRepository ~= "exit" then
            screen = pendingRepository or "repositories"
            pendingRepository = nil
            needsDraw = true
        else
            net.wifiDisconnect()
            sys.exit()
            return
        end
    end

    if needsDraw then render() end
end