--!A cross-platform build utility based on Lua
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
-- Copyright (C) 2015-present, Xmake Open Source Community.
--
-- @author      ruki
-- @file        build_wasm_app.lua
--

import("core.base.semver")

-- Fix Emscripten JS issues for Qt WASM builds
function _fix_emscripten_js(jsfile)
    if not os.isfile(jsfile) then
        return
    end

    -- Remove "use strict"; to avoid issues with `this` being undefined in strict mode
    io.gsub(jsfile, "\"use strict\";", "")
    io.gsub(jsfile, "'use strict';", "")
    -- Patch visualViewport access issue if present (undefined this context)
    io.gsub(jsfile, "this%.visualViewport",
        "(typeof window !== 'undefined' ? window.visualViewport : null)")
    -- Guard all document.querySelector(target) calls with try-catch.
    -- Qt WASM uses "!" prefixed selectors that are not valid CSS selectors,
    -- and corrupted strings from SharedArrayBuffer can also cause SyntaxErrors.
    io.gsub(jsfile, "document%.querySelector%(target%)",
        "(function(){try{return document.querySelector(target)}catch(e){return null}})()")
    -- Replace findCanvasEventTarget with a robust version.
    -- Qt WASM registers canvases in Module.specialHTMLTargets with "!" prefixed
    -- keys (e.g. "!qtwindow1", "!qtoffscreen_xxx"). With pthreads +
    -- ALLOW_MEMORY_GROWTH, Emscripten's UTF8ToString may read corrupted strings
    -- from SharedArrayBuffer memory, causing the specialHTMLTargets lookup to fail.
    -- Additionally, QWasmOffscreenSurface passes an empty string when
    -- OffscreenCanvas is unavailable. The replacement adds a fallback that
    -- iterates specialHTMLTargets to find any Qt-registered canvas element.
    local content = io.readfile(jsfile)
    local marker = "var findCanvasEventTarget = target => {"
    local pos = content:find(marker, 1, true)
    if pos then
        -- Find the end of the function by counting matched braces
        local depth = 1
        local i = pos + #marker
        while i <= #content and depth > 0 do
            local c = content:sub(i, i)
            if c == "{" then depth = depth + 1
            elseif c == "}" then depth = depth - 1 end
            i = i + 1
        end
        if content:sub(i, i) == ";" then i = i + 1 end
        local new_func = "var findCanvasEventTarget = target => {\n"
            .. " target = maybeCStringToJsString(target);\n"
            .. " if (specialHTMLTargets[target]) return specialHTMLTargets[target];\n"
            .. " if (GL.offscreenCanvases[target]) return GL.offscreenCanvases[target];\n"
            .. " if (typeof target === 'string' && target.length > 0) {\n"
            .. "  var s = target.substr(1);\n"
            .. "  if (GL.offscreenCanvases[s]) return GL.offscreenCanvases[s];\n"
            .. " }\n"
            .. " if (target === 'canvas') {\n"
            .. "  var k = Object.keys(GL.offscreenCanvases);\n"
            .. "  if (k.length) return GL.offscreenCanvases[k[0]];\n"
            .. " }\n"
            .. " for (var key in specialHTMLTargets) {\n"
            .. "  if (typeof key === 'string' && key.charAt(0) === '!') {\n"
            .. "   var el = specialHTMLTargets[key];\n"
            .. "   if (el && (el.tagName === 'CANVAS' || (typeof OffscreenCanvas !== 'undefined' && el instanceof OffscreenCanvas))) return el;\n"
            .. "  }\n"
            .. " }\n"
            .. " try { return typeof document !== 'undefined' ? document.querySelector(target) : undefined; }\n"
            .. " catch(e) { return undefined; }\n"
            .. "};\n"
        content = content:sub(1, pos - 1) .. new_func .. content:sub(i)
        io.writefile(jsfile, content)
    end
end

function main(target)
    local qt = target:data("qt")
    local pluginsdir = qt and qt.pluginsdir
    if not pluginsdir then
        return
    end
    local targetdir = target:targetdir()
    local htmlfile = path.join(targetdir, target:basename() .. ".html")
    if os.isfile(path.join(pluginsdir, "platforms/wasm_shell.html")) then
        os.vcp(path.join(pluginsdir, "platforms/wasm_shell.html"), htmlfile)
        io.gsub(htmlfile, "@APPNAME@", target:name())
        local qt_sdkver = qt.sdkver or target:data("qt_sdkver")
        if qt_sdkver and semver.new(qt_sdkver):ge("6.0") then
            io.gsub(htmlfile, "@APPEXPORTNAME@", "createQtAppInstance")
            local preload = ""
            -- @see https://github.com/xmake-io/xmake/issues/6182
            local preloadfiles = target:values("wasm.preloadfiles")
            if preloadfiles then
                local filelist = {}
                for _, preloadfile in ipairs(preloadfiles) do
                    table.insert(filelist, string.format("'%s'", path.filename(preloadfile)))
                end
                if #filelist > 0 then
                    preload = string.format("preload: [%s],", table.concat(filelist, ", "))
                end
            end
            -- Patch old containerElements (pre-Qt 6.5)
            io.gsub(htmlfile, "containerElements: %[screen%],", function (w)
                return w .. " " .. preload
            end)
            -- Patch new qtContainerElements (Qt 6.5+)
            io.gsub(htmlfile, "qtContainerElements: %[screen%],", function (w)
                return w .. " " .. preload
            end)
            io.gsub(htmlfile, "@PRELOAD@", "")
            _fix_emscripten_js(path.join(targetdir, target:basename() .. ".js"))
        end
        os.vcp(path.join(pluginsdir, "platforms/qtloader.js"), targetdir)
        os.vcp(path.join(pluginsdir, "platforms/qtlogo.svg"), targetdir)
    end
end