OC-WEB 1.0: An Web Browser For OpenComputers!

local component = require("component")
local event = require("event")
local internet = require("internet")
local term = require("term")
local unicode = require("unicode")

local gpu = component.gpu
local hasColor = gpu.getDepth() > 1

local function bootUpScreen()
    term.clear()
    local logo = [[
 ::::::::   ::::::::               :::       ::: :::::::::: :::::::::
:+:    :+: :+:    :+:              :+:       :+: :+:        :+:    :+:
+:+    +:+ +:+                     +:+       +:+ +:+        +:+    +:+
+#+    +:+ +#+       +#++:++#++:++ +#+  +:+  +#+ +#++:++#   +#++:++#+
+#+    +#+ +#+                     +#+ +#+#+ +#+ +#+        +#+    +#+
#+#    #+# #+#    #+#               #+#+# #+#+#  #+#        #+#    #+#
 ########   ########                 ###   ###   ########## #########
    ]]
    term.setCursor(1, 1)
    term.write(logo)
    term.setCursor(1, select(2, term.getCursor()) + 1)
    term.write("Loading...")
    term.setCursor(1, select(2, term.getCursor()) + 2)
    term.write("OC-WEB: A Web Browser For OpenComputers Coded by nonogamer9")
    os.sleep(3)
end

local function resolveURL(base, relative)
    if not base or not relative then return nil end
    if relative:match("^https?://") then return relative end
    if relative:sub(1, 1) == "/" then
        return base:match("^(https?://[^/]+)") .. relative
    else
        local baseMatch = base:match("^(https?://.*/)") or base:match("^(https?://[^/]+)")
        if baseMatch then
            if baseMatch:sub(-1) ~= "/" then
                baseMatch = baseMatch .. "/"
            end
            return baseMatch .. relative
        else
            return nil
        end
    end
end

local function handleJavaScript(html, currentBaseURL)
    local redirectUrl = html:match("window%.location%s*=%s*['\"](.-)['\"]")
    if redirectUrl then
        return resolveURL(currentBaseURL, redirectUrl)
    end
    return nil
end

local function fetch(url, visited)
    visited = visited or {}
    if visited[url] then
        return false, "Redirect loop detected"
    end
    visited[url] = true

    local handle, err = internet.request(url)
    if not handle then
        return false, "Failed to connect to " .. url .. ": " .. (err or "unknown error")
    end

    local data = ""
    for chunk in handle do
        if chunk then
            data = data .. chunk
        end
    end

    local redirectUrl = data:match('<meta%s+http%-equiv="refresh"%s+content=".-;url=(.-)"')
    if redirectUrl then
        local resolvedRedirectUrl = resolveURL(url, redirectUrl)
        if resolvedRedirectUrl then
            print("Redirecting to: " .. resolvedRedirectUrl)
            return fetch(resolvedRedirectUrl, visited)
        else
            return false, "Invalid redirect URL: " .. redirectUrl
        end
    end

    local jsRedirectUrl = handleJavaScript(data, url)
    if jsRedirectUrl then
        print("JavaScript redirecting to: " .. jsRedirectUrl)
        return fetch(jsRedirectUrl, visited)
    end

    return true, data
end

local function parseHTML(html)
    local links = {}
    html = html:gsub("<script.->.-</script>", "")
    html = html:gsub("<style.->.-</style>", "")
    html = html:gsub("<b>(.-)</b>", function(content) return "[B]" .. content .. "[/B]" end)
    html = html:gsub("<strong>(.-)</strong>", function(content) return "[B]" .. content .. "[/B]" end)
    html = html:gsub("<i>(.-)</i>", function(content) return "[I]" .. content .. "[/I]" end)
    html = html:gsub("<em>(.-)</em>", function(content) return "[I]" .. content .. "[/I]" end)
    html = html:gsub("<u>(.-)</u>", function(content) return "[U]" .. content .. "[/U]" end)
    html = html:gsub("<a href=\"(.-)\">(.-)</a>", function(href, content)
        table.insert(links, {href = href, content = content})
        return content .. " [" .. #links .. "]"
    end)
    html = html:gsub("<h[1-6]>(.-)</h[1-6]>", function(content) return "[H]" .. content .. "[/H]" end)
    html = html:gsub("<li>(.-)</li>", function(content) return " * " .. content end)
    html = html:gsub("<br>", "\n")
    html = html:gsub("<p>", "\n\n")
    html = html:gsub("</p>", "\n\n")
    html = html:gsub("<div>(.-)</div>", function(content) return content .. "\n" end)
    html = html:gsub("<.->", "")
    html = html:gsub("&lt;", "<")
    html = html:gsub("&gt;", ">")
    html = html:gsub("&amp;", "&")
    html = html:gsub("&quot;", "\"")
    html = html:gsub("&apos;", "'")
    return html, links
end

local function display(baseURL, data, links)
    local lines = {}
    for line in data:gmatch("[^\r\n]+") do
        table.insert(lines, line)
    end

    local offset = 0
    local screenWidth, screenHeight = gpu.getResolution()
    local contentHeight = screenHeight - 1

    local function redraw()
        term.setCursor(1, 1)
        for i = 1, contentHeight do
            local line = lines[i + offset] or ""
            term.setCursor(1, i)
            term.clearLine()
            term.write(unicode.sub(line, 1, screenWidth))
        end

        term.setCursor(1, screenHeight)
        gpu.setBackground(0x333333)
        term.clearLine()
        term.write("URL: " .. (baseURL or "N/A") .. " | Use Arrow Keys to Scroll, Q to Quit, U to Change URL")
        gpu.setBackground(0x000000)
    end

    redraw()

    while true do
        local eventType, _, _, y, _, scrollDirection = event.pull()
        local needsRedraw = false
        if eventType == "key_down" then
            if y == 200 then
                offset = math.max(0, offset - 1)
                needsRedraw = true
            elseif y == 208 then
                offset = math.min(#lines - contentHeight, offset + 1)
                needsRedraw = true
            elseif y == 16 then
                break
            elseif y == 22 then
                return false
            end
        elseif eventType == "scroll" then
            if scrollDirection == 1 then
                offset = math.max(0, offset - 1)
                needsRedraw = true
            elseif scrollDirection == -1 then
                offset = math.min(#lines - contentHeight, offset + 1)
                needsRedraw = true
            end
        elseif eventType == "touch" then
            local lineIndex = y + offset
            if lineIndex <= #lines then
                local line = lines[lineIndex]
                local linkIndex = line:match("%[(%d+)%]$")
                if linkIndex then
                    local link = links[tonumber(linkIndex)]
                    if link and link.href then
                        local resolvedURL = resolveURL(baseURL, link.href)
                        if resolvedURL then
                            print("Opening link: " .. resolvedURL)
                            local success, newData = fetch(resolvedURL)
                            if success then
                                local newParsedData, newLinks = parseHTML(newData)
                                display(resolvedURL, newParsedData, newLinks)
                            else
                                print("Error fetching URL: " .. newData)
                            end
                        else
                            print("Invalid URL: " .. tostring(link.href))
                        end
                    else
                        print("Invalid link at index: " .. linkIndex)
                    end
                end
            end
        end
        if needsRedraw then
            redraw()
        end
    end
end

function main(showBootScreen)
    if showBootScreen then
        bootUpScreen()
    end
    term.clear()
    print("Enter a URL:")
    local url = io.read()
    if not url:match("^https?://") then
        print("Invalid URL. Please include http:// or https://")
    else
        local success, data = fetch(url)
        if success then
            local parsedData, links = parseHTML(data)
            if display(url, parsedData, links) == false then
                main(false)
            end
        else
            print("Error fetching URL: " .. data)
        end
    end
end

main(true)