#!/usr/bin/env luajit
--[[
    Abrechenbarkeit - A simple trust-based ledger
    Copyright 2024 metamuffin
    Copyright 2024 dasriley

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, version 3 of the License only.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
]] --

local function escape(s)
    return s:gsub("<", "&lt;"):gsub("<", "&lt;")
end

local function urldecode(s)
    if s == nil then return nil end
    return s:gsub("+", " "):gsub("%%20", " ")
end

local function urlencode(s)
    if s == nil then return nil end
    return s:gsub(" ", "%%20")
end

local function parse_query(q)
    if q == nil then return {} end
    local data = {}
    for pair in string.gmatch(q, "([^&]+)") do
        local flag = string.match(pair, "^([^=]+)$")
        if flag ~= nil then
            data[flag] = "1"
        else
            local key, value = string.match(pair, "^([^=]+)=([^=]*)$")
            if key ~= nil and value ~= nil then
                data[key] = urldecode(value)
            end
        end
    end
    return data
end

local function load_config()
    local log = io.open("config", "r")
    if log == nil then return {} end
    local config = {}
    for l in log:lines("l") do
        if l ~= "" and l[0] ~= "#" then
            local key, value = string.match(l, "^([^=]+)=([^=]*)")
            if key ~= nil and value ~= nil then
                config[key] = value
            end
        end
    end
    return config
end

local function load_translations(langs)
    local t = {}
    for _, lcode in ipairs(langs) do
        local file = io.open(string.format("locale/%s.ini", lcode), "r")
        if file ~= nil then
            for l in file:lines("l") do
                if l ~= "" then
                    local key, value = string.match(l, "^([^=]+)=([^=]*)")
                    if key ~= nil and value ~= nil then
                        t[key] = value
                    end
                end
            end
        end
    end
    return t
end

local config = load_config()
local path = os.getenv("PATH_INFO")
local method = os.getenv("REQUEST_METHOD")
local query = parse_query(os.getenv("QUERY_STRING"))
local translations = load_translations({ "en", config.language })

local stylesheet = io.open("style.css"):read("a")
local script = io.open("script.js"):read("a")

local function format(template, params)
    params = params or {}
    if template == nil then return "NIL TEMPLATE" end
    return string.gsub(template, "{([%w_\\.!]+)}", function(n)
        local raw = n:sub(1, 1) ~= "!"
        if not raw then n = n:sub(2) end
        local s = format(params[n] or translations[n] or "NIL PARAM", params)
        return raw and s or escape(s)
    end)
end

local function format_amount(amount, tag, classes)
    local s = string.format("%.02f%s", amount / 100, config.unit or "€")
    if tag == nil then return s end
    return string.format([[<%s class="amount-%s %s">%s</%s>"]], tag, amount >= 0 and "pos" or "neg", s, tag, classes or "")
end

local function get_user_theme(username)
    local c = ""
    if username == "_jeb" then
        c = "html { animation: 2s jeb infinite; }"
        c = c .. "@keyframes jeb {\n"
        for i = 0, 100 do
            c = c .. string.format("%.02f%% { --hue: %.02f; } \n", i, i / 100 * 360)
        end
        c = c .. "\n}"
    elseif username == "Dinnerbone" then
        c = "html { transform: scale(-1); } "
    end
    return c
end

local function format_duration(t)
    if t > 86400 then return string.format("%d day%s", t / 86400, math.floor(t / 86400) ~= 1 and "s" or "") end
    if t > 3600 then return string.format("%d hour%s", t / 3600, math.floor(t / 3600) ~= 1 and "s" or "") end
    if t > 60 then return string.format("%d minute%s", t / 60, math.floor(t / 60) ~= 1 and "s" or "") end
    return string.format("%d seconds", t)
end

local function respond(status, title, body)
    print(string.format("Status: %d", status))
    print("Content-Type: text/html")
    print("")
    print(format([[
        <!DOCTYPE html>
        <html><head>
            <title>{title}</title>
            <meta charset="utf-8" />
            <style>{style}</style>
            <style>{user_style}</style>
            <script>{script}</script>
            {head_extra}
        </head>
        <body>
            <nav>
                <a class="logo" href="/">
					<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-receipt-cutoff" viewBox="0 0 16 16">
					  <path d="M3 4.5a.5.5 0 0 1 .5-.5h6a.5.5 0 1 1 0 1h-6a.5.5 0 0 1-.5-.5m0 2a.5.5 0 0 1 .5-.5h6a.5.5 0 1 1 0 1h-6a.5.5 0 0 1-.5-.5m0 2a.5.5 0 0 1 .5-.5h6a.5.5 0 1 1 0 1h-6a.5.5 0 0 1-.5-.5m0 2a.5.5 0 0 1 .5-.5h6a.5.5 0 0 1 0 1h-6a.5.5 0 0 1-.5-.5m0 2a.5.5 0 0 1 .5-.5h6a.5.5 0 0 1 0 1h-6a.5.5 0 0 1-.5-.5M11.5 4a.5.5 0 0 0 0 1h1a.5.5 0 0 0 0-1zm0 2a.5.5 0 0 0 0 1h1a.5.5 0 0 0 0-1zm0 2a.5.5 0 0 0 0 1h1a.5.5 0 0 0 0-1zm0 2a.5.5 0 0 0 0 1h1a.5.5 0 0 0 0-1zm0 2a.5.5 0 0 0 0 1h1a.5.5 0 0 0 0-1z"/>
					  <path d="M2.354.646a.5.5 0 0 0-.801.13l-.5 1A.5.5 0 0 0 1 2v13H.5a.5.5 0 0 0 0 1h15a.5.5 0 0 0 0-1H15V2a.5.5 0 0 0-.053-.224l-.5-1a.5.5 0 0 0-.8-.13L13 1.293l-.646-.647a.5.5 0 0 0-.708 0L11 1.293l-.646-.647a.5.5 0 0 0-.708 0L9 1.293 8.354.646a.5.5 0 0 0-.708 0L7 1.293 6.354.646a.5.5 0 0 0-.708 0L5 1.293 4.354.646a.5.5 0 0 0-.708 0L3 1.293zm-.217 1.198.51.51a.5.5 0 0 0 .707 0L4 1.707l.646.647a.5.5 0 0 0 .708 0L6 1.707l.646.647a.5.5 0 0 0 .708 0L8 1.707l.646.647a.5.5 0 0 0 .708 0L10 1.707l.646.647a.5.5 0 0 0 .708 0L12 1.707l.646.647a.5.5 0 0 0 .708 0l.509-.51.137.274V15H2V2.118z"/>
					</svg>
                    {appname}
                </a>
                <a href="/?log">{log}</a>
                <a href="/?products">{products}</a>
                <a href="/?about">{about}</a>
            </nav>
    ]], {
        title = escape(title),
        style = stylesheet,
        user_style = get_user_theme(path and path:sub(2)),
        script = script,
        head_extra = config.head_extra or ""
    }))
    body()
    print("</body></html>")
end

local function error_box(message)
    return string.format([[<div class="notif error"><p>Error: %s</p></div>]], message)
end

local function respond_error(message)
    respond(400, "Error", function()
        print(error_box(message))
    end)
end

local function redirect(path)
    print("Status: 307")
    print(string.format("Location: %s", path))
    print()
end

local function form_data()
    return parse_query(io.read())
end

local function read_log()
    local log = io.open("log", "r")
    if log == nil then
        return function() return nil end
    end
    local lines = log:lines("l")
    return function()
        local l = lines()
        if l == "" or l == nil then
            return nil
        end
        local time, username, amount, pcode, pcount, comment = string.match(l,
            "(%d+),([%w_ -]+),(-?%d+),([%w_-]*),(-?%d*),([%w_ -]*)")
        return tonumber(time), username, tonumber(amount), pcode, tonumber(pcount), comment
    end
end

local function read_products()
    local log = io.open("products", "r")
    if log == nil then
        return function() return nil end
    end
    local lines = log:lines("l")
    return function()
        local l = lines()
        if l == "" or l == nil then
            return nil
        end
        local barcode, price, name, owner = string.match(l, "([%w_-]+),(-?%d+),([%w_ -]*),([%w_ -]*)")
        return barcode, tonumber(price), name, owner
    end
end

local function balances()
    local users = {}
    for _, username, amount, _, _, _ in read_log() do
        users[username] = (users[username] or 0) + amount
    end
    return users
end

local function product_balances()
    local products = {}
    for _, _, _, pcode, pcount, _ in read_log() do
        if pcode ~= nil and pcount ~= nil then
            products[pcode] = (products[pcode] or 0) + pcount
        end
    end
    return products
end

local function last_txns()
    local users = {}
    for time, username, _, _, _, _ in read_log() do
        users[username] = time
    end
    return users
end

local function get_active_users()
    local user_balances = {}
    for time, username, amount, _, _, _ in read_log() do
        user_balances[username] = {
            time = time,
            username = username,
            balance = (user_balances[username] or { balance = 0 }).balance + amount
        }
    end

    local users = {}
    for _, user in pairs(user_balances) do
        table.insert(users, user)
    end

    table.sort(users, function(a, b) return a.time > b.time end)
    return users
end

local function r_user_post(username)
    local data = form_data()
    local amount = tonumber(data.amount)
    local comment = data.comment
    local pcode = nil
    local pcount = nil
    local powner = nil
    local powner_comment = nil
    if data.pcode then
        for p_barcode, p_amount, p_name, p_owner in read_products() do
            if p_barcode == data.pcode then
                powner = p_owner
                pcount = (tonumber(data.pcount) or 1) * (data.negate_pcount ~= nil and -1 or 1)
                pcode = p_barcode
                if amount == nil then amount = pcount * p_amount end
                if comment == nil then
                    comment = string.format("%s %d %s", pcount < 0 and "Buy" or "Restock",
                        math.abs(pcount), p_name)

                    powner_comment = string.format("%s %d %s %s %s",
                        pcount < 0 and "Sell" or "Restock",
                        math.abs(pcount), p_name,
                        pcount < 0 and "to" or "by",
                        username)
                end
            end
        end
        if amount == nil then
            return error_box("unknown product")
        end
    end
    if amount == nil then
        return error_box("amount invalid")
    end
    if comment == nil or comment:match("^[%w_ -]*$") == nil then
        return error_box("comment invalid")
    end
    local log = io.open("log", "a+")
    if log == nil then
        return error_box("failed to open log")
    end
    local time = os.time()
    -- subtract from buyer
    log:write(string.format("%d,%s,%d,%s,%s,%s\n", time, username, amount, pcode or "", pcount or "", comment))
    -- add to owner
    if powner then
        -- count is always zero as doesn't affect stock
        log:write(string.format("%d,%s,%d,%s,%s,%s\n", time, powner, -amount, pcode or "", "", powner_comment))
    end
    log:flush()
    log:close()
    return format([[
        <div class="notif"><p>Transaction successful: {amount} ({!comment})</p></div>
        <audio src="{sound}" autoplay></audio>
    ]], {
        sign = amount >= 0 and "pos" or "neg",
        amount = format_amount(amount, "strong"),
        comment = escape(comment),
        sound = config.transaction_sound or ""
    })
end

local function r_user(username)
    local notif = nil
    if method == "POST" then
        notif = r_user_post(username)
    end
    return respond(200, string.format("Abrechenbarheit: %s", username), function()
        print(format("<h1>{username}</h1>", { username = username }))
        local balance = balances()[username]
        local last_txn = last_txns()[username]
        local new_user = balance == nil
        balance = balance or 0
        if notif then print(notif) end
        if new_user then
            print([[<div class="notif"><p><i>{user.lazy_creation}</i></p></div>]])
        else
            print([[<div class="backgroundbox userinfo">]])
            print(format([[{user.balance}: <br>{amount}<br>]],
                { sign = balance >= 0 and "pos" or "neg", amount = format_amount(balance, "span", "balance-value") }))
            print(format([[{user.last_txn} <a href="/{username}?log">{user.view_log}</a>]],
                { time = format_duration(os.time() - last_txn), username = urlencode(username) }))
            print([[</div>]])
        end
        print([[<div class="transactions container firstchildlarge">]])
        print([[<div class="amount-presets backgroundbox">]])
        for _, type in ipairs({ 1, -1 }) do
            for _, amount in ipairs({ 50, 100, 150, 200, 500, 1000 }) do
                print(string.format([[
                    <form action="" method="POST">
                        <input type="number" name="amount" id="amount" value="%d" hidden />
                        <input type="text" name="comment" id="comment" value="" hidden />
                        <input type="submit" value="%s%.02f€" class="amount-%s button" />
                    </form>
                    ]], amount * type, ({ [-1] = "-", [1] = "+" })[type], amount / 100,
                    ({ [-1] = "neg", [1] = "pos" })[type]))
            end
        end
        print("</div>")
        print(format([[
            <form class="transaction box backgroundbox" action="" method="POST">
                <h3>{user.form.transaction}</h3>
                <label for="amount">Amount (ct): </label>
                <input type="number" name="amount" id="amount" />
                <label for="comment">Comment: </label>
                <input type="text" name="comment" id="comment" />
                <input type="submit" value="{user.form.transaction.submit}" class="amount-ntr button" />
            </form>
            <form class="transaction box backgroundbox" action="" method="POST" id="buy_product">
                <h3>{user.form.buy}</h3>
                <input type="text" name="negate_pcount" value="1" hidden />
                <label for="pcount">Count: </label>
                <input type="number" name="pcount" id="pcount" value="1" />
                <label for="pcode">{field.barcode}: </label>
                <input type="text" name="pcode" id="pcode" />
                <input class="amount-neg button" type="submit" value="{user.form.buy.submit}" />
            </form>
            <form class="transaction box backgroundbox" action="" method="POST" id="buy_product">
                <h3>{user.form.restock}</h3>
                <label for="pcount">{field.count}: </label>
                <input type="number" name="pcount" id="pcount" value="1" />
                <label for="amount">{field.upstream_price}: </label>
                <input type="number" name="amount" id="amount" />
                <label for="pcode">{field.barcode}: </label>
                <input type="text" name="pcode" id="pcode" />
                <input type="submit" value="{user.form.restock.submit}" class="button amount-pos" />
            </form>
        ]]))
        print("</div>")
    end)
end

local function r_log(filter)
    return respond(200, "Abrechnungen", function()
        print([[<table class="log"]])
        print([[<thead><tr>
            <th>Time</th>
            <th>Username</th>
            <th>Amount</th>
            <th>P.-Barcode</th>
            <th>P.-Count</th>
            <th>Comment</th>
            <th>Actions</th>
        </tr></thead>]])
        print("<tbody>")
        for time, username, amount, pcode, pcount, comment in read_log() do
            if filter == nil or filter == username then
                print(string.format([[
                    <tr>
                        <td>%s (%s ago)</td>
                        <td>%s</td>
                        <td class="amount-%s">%.02f€</td>
                        <td>%s</td>
                        <td>%s %s</td>
                        <td>%s</td>
                        <td>
                            <form action="/%s" method="POST">
                                <input type="number" name="amount" id="amount" value="%d" hidden />
                                <input type="text" name="comment" id="comment" value="Revert %s" hidden />
                                <input type="submit" class="amount-ntr button" value="Revert" />
                            </form>
                        </td>
                    </tr>
                ]],
                    os.date("!%Y-%m-%dT%H:%M:%SZ", time), format_duration(os.time() - time),
                    escape(username),
                    amount >= 0 and "pos" or "neg", amount / 100,
                    escape(pcode) or "",
                    pcount and (pcount < 0 and "buy" or "stock") or "", pcount and tostring(math.abs(pcount)) or "",
                    escape(comment),
                    escape(username),
                    -amount,
                    escape(comment)
                ))
            end
        end
        print("</tbody>")
        print("</table>")
    end)
end

local function r_index()
    return respond(200, "Abrechenbarkeit", function()
        print([[
            <form action="/" method="GET" id="user_creation">
                <h3>User Creation</h3>
                <label for="username">Username: </label>
                <input type="text" name="create_user" id="username" />
                <input type="submit" value="Continue" class="button amount-ntr" />
            </form>
        ]])
        print([[<div class="userlist"></div>]]) -- for printing
        print([[<ul class="userlist">]])
        for _, user in ipairs(get_active_users()) do
            print(string.format([[
                <li><a href="/%s"><span class="name">%s</span> <span class="amount amount-%s">%.02f€</span></a></li>
            ]],
                urlencode(user.username),
                escape(user.username),
                user.balance >= 0 and "pos" or "neg", user.balance / 100
            ))
        end
        print("</ul>")
    end)
end

local function validate_username(username)
    -- disallow leading or traling whitespace
    return username ~= nil
        and username:match("^([%w_ -]+)$") ~= nil
        and username:match("^%s") == nil
        and username:match("%s$") == nil
end

local function r_create_user()
    local username = query.create_user
    if not validate_username(username) then
        return respond_error("invalid username " .. username)
    end
    return redirect(string.format("/%s", urlencode(username)))
end

local function r_products_post()
    local data = form_data()
    local barcode = data.barcode
    if barcode == nil then
        return error_box("barcode unset")
    end
    if barcode:match("^[%w_-]*$") == nil then
        return error_box("barcode invalid")
    end
    if data.delete then
        local new_products = io.open("products.new", "w+")
        if new_products == nil then
            return error_box("failed to open new products")
        end
        for a_barcode, price, name, owner in read_products() do
            if barcode ~= a_barcode then
                new_products:write(string.format("%s,%d,%s,%s\n", a_barcode, price, name, owner))
            end
        end
        new_products:flush()
        new_products:close()
        os.rename("products.new", "products")
    else
        local price = tonumber(data.price)
        local name = data.name
        if price == nil then
            return error_box("price invalid")
        end
        if name:match("^[%w_ -]*$") == nil then
            return error_box("name invalid")
        end
        local products = io.open("products", "a+")
        if products == nil then
            return error_box("failed to open products")
        end
        local owner = data.owner or ""
        if name:match("^[%w_ -]*$") == nil then
            return error_box("owner invalid")
        end
        products:write(string.format("%s,%d,%s,%s\n", barcode, price, name, owner))
        products:flush()
        products:close()
    end
end

local function r_products()
    local notif = nil
    if method == "POST" then
        notif = r_products_post()
    end
    respond(200, "Abrechenbare Product List", function()
        print("<h1>Product List</h1>")
        if notif then print(notif) end
        print([[
        	<div class="container">
            <form action="/?products" method="POST" class="box backgroundbox">
                <h3>Add Product</h3>
                <label for="name">Name: </label>
                <input type="text" name="name" id="name" />
                <label for="price">Price (ct): </label>
                <input type="number" name="price" id="price" />
                <label for="owner">Owner: </label>
                <input type="text" name="owner" id="owner" />
                <label for="barcode">Barcode: </label>
                <input type="text" name="barcode" id="barcode" />
                <input type="submit" value="Add" class="amount-ntr button" />
            </form>
            <form action="/?products" method="POST" class="box backgroundbox">
                <h3>Remove Product</h3>
                <input type="text" name="delete" value="1" hidden />
                <label for="barcode">Barcode: </label>
                <input type="text" name="barcode" id="barcode" />
                <input type="submit" value="Remove"class="amount-ntr button" />
            </form>
            </div>
        ]])
        print([[<table class="productlist"><tr>
            <th>Name</th>
            <th>Price</th>
            <th>Barcode</th>
            <th>Count</th>
            <th>Owner</th>
        </tr>]])
        local pbals = product_balances()
        for barcode, price, name, owner in read_products() do
            print(string.format([[
                <tr><td>%s</td><td class="amount-%s">%.02f€</td><td>%s</td><td>%s</td><td>%s</td></tr>
            ]],
                name,
                -price >= 0 and "pos" or "neg", -price / 100,
                barcode,
                pbals[barcode] or "0",
                owner
            ))
        end
        print("</table>")
    end)
end

local function r_about()
    respond(200, "About Abrechenbarkeit", function()
        print([[
            <h1>About Abrechenbarkeit</h1>
            <p>Abrechenbarkeit is a simple trust-based ledger for keeping track of money spent on product.</p>
            <p>Abrechenbarkeit is free software. It is licensed exclusively GNU Affero General Public License Version 3 only.<p>
            <p>The source code is published on <a href="https://codeberg.org/metamuffin/strichliste">Codeberg</a>. This is also where <a href="https://codeberg.org/metamuffin/strichliste/issues">issues with this software</a> should be reported.</p>
            <p>Thanks for choosing Abrechenbarkeit.</p>
        ]])
    end)
end

local function extract_username()
    if path == nil then
        return respond_error("no path")
    end
    local username = urldecode(path:sub(2))
    if username == nil or username:match("^([%w_ -]+)$") == nil then
        return nil
    end
    return username
end

if path == "/" then
    if query.about then
        return r_about()
    elseif query.products then
        return r_products()
    elseif query.log then
        return r_log()
    elseif query.create_user then
        return r_create_user()
    else
        return r_index()
    end
else
    local username = extract_username()
    if username == nil or not validate_username(username) then
        return respond_error("username invalid")
    elseif query.log then
        return r_log(username)
    else
        return r_user(username)
    end
end