Bank Database

-- PocketOS bank server: stores everyone's money.
--
-- Setup: pick a computer with a wireless modem, set `bank = <its ID>`
-- in /pocketos/config.lua (on every device), and reboot it - it boots
-- into the bank automatically, just like the tracker hub. Accounts are
-- keyed by pocket computer ID and saved in /.bank.
--
-- Deposits come from ATMs (see atm.lua); payments come from the Bank
-- app on pockets. The bank messages people their receipts.

-------------------------------------------------- CONFIG - edit me --

-- Only these computer IDs may submit ATM deposits, e.g. { 12, 15 }.
-- nil = accept deposits from any computer (fine among friends).
local ATMS = nil

-- Balance for brand-new accounts.
local START = 0

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

local DATA = "/.bank"

local accounts = {}
if fs.exists(DATA) then
    local f = fs.open(DATA, "r")
    accounts = textutils.unserialize(f.readAll() or "") or {}
    f.close()
end

local function save()
    local f = fs.open(DATA, "w")
    f.write(textutils.serialize(accounts))
    f.close()
end

local MDATA = "/.market"
local market = { nextId = 1, items = {} }
if fs.exists(MDATA) then
    local f = fs.open(MDATA, "r")
    local v = textutils.unserialize(f.readAll() or "")
    f.close()
    if type(v) == "table" and type(v.items) == "table" then market = v end
end

local function saveMarket()
    local f = fs.open(MDATA, "w")
    f.write(textutils.serialize(market))
    f.close()
end

local hasModem = false
for _, side in ipairs(peripheral.getNames()) do
    if peripheral.getType(side) == "modem" then
        if pcall(rednet.open, side) then hasModem = true end
    end
end
if not hasModem then
    print("Attach a wireless modem first!")
    return
end
rednet.host("pocketos.bank", "bank" .. os.getComputerID())

-- admin safety: only these IDs may read the transaction ledger
local admins = { 11, 18 }
do
    local ok, cfg = pcall(dofile, "/pocketos/config.lua")
    if ok and type(cfg) == "table" and type(cfg.admins) == "table" then
        admins = cfg.admins
    end
end
local function isAdmin(id)
    for _, a in ipairs(admins) do
        if tonumber(a) == tonumber(id) then return true end
    end
    return false
end

local log = {}
local function addLog(s)
    local ok, t = pcall(os.date, "%H:%M ")
    table.insert(log, 1, (ok and t or "") .. s)
    while #log > 12 do table.remove(log) end
end

-- persistent transaction history for the developer Ledger view
local TDATA = "/.bank_txns"
local txns = {}
if fs.exists(TDATA) then
    local f = fs.open(TDATA, "r")
    txns = textutils.unserialize(f.readAll() or "") or {}
    f.close()
end

local function record(kind, from, to, amount)
    local ok, t = pcall(os.date, "%H:%M")
    table.insert(txns, 1, {
        kind = kind, from = from, to = to, amount = amount,
        time = ok and t or "",
    })
    while #txns > 200 do table.remove(txns) end
    local f = fs.open(TDATA, "w")
    f.write(textutils.serialize(txns))
    f.close()
end

local function get(id)
    local key = tostring(id)
    local acc = accounts[key]
    if not acc then
        acc = { bal = START }
        accounts[key] = acc
    end
    return acc
end

local function notify(id, text)
    rednet.send(tonumber(id), { text = text, label = "Bank" }, "pocketos")
end

local color = term.isColor and term.isColor()
local function tint(c)
    if color then term.setTextColor(c) end
end

local function draw()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)
    term.clear()
    local w, h = term.getSize()
    term.setCursorPos(1, 1)
    tint(colors.yellow)
    write("PocketOS Bank - computer #" .. os.getComputerID())
    local n, total = 0, 0
    for _, acc in pairs(accounts) do
        n = n + 1
        total = total + (acc.bal or 0)
    end
    term.setCursorPos(1, 2)
    tint(colors.lightGray)
    write(n .. " accounts, $" .. total .. " in circulation, "
        .. #market.items .. " listings")
    term.setCursorPos(1, 4)
    write("Recent:")
    tint(colors.white)
    for i, s in ipairs(log) do
        if 4 + i > h - 1 then break end
        term.setCursorPos(1, 4 + i)
        write(s:sub(1, w))
    end
    term.setCursorPos(1, h)
    tint(colors.gray)
    write("Hold Ctrl+T to stop")
end

local function allowedATM(id)
    if not ATMS then return true end
    for _, a in ipairs(ATMS) do
        if a == id then return true end
    end
    return false
end

addLog("Bank started")
draw()
while true do
    local id, msg = rednet.receive("pocketos.bank")
    if type(msg) == "table" and type(msg.type) == "string" then
        local reply
        if msg.type == "balance" then
            local acc = get(id)
            if type(msg.label) == "string" and #msg.label > 0 then
                acc.label = msg.label:sub(1, 12)
                save()
            end
            reply = { ok = true, balance = acc.bal, label = acc.label }
        elseif msg.type == "info" then
            local account = tonumber(msg.account)
            if account then
                local acc = get(account)
                reply = { ok = true, balance = acc.bal, label = acc.label }
            else
                reply = { ok = false, err = "Bad account" }
            end
        elseif msg.type == "deposit" then
            local account = tonumber(msg.account)
            local amount = tonumber(msg.amount)
            amount = amount and math.floor(amount)
            if not allowedATM(id) then
                reply = { ok = false, err = "ATM not authorised" }
            elseif not account or not amount or amount <= 0
                or amount > 1000000000 then
                reply = { ok = false, err = "Bad deposit" }
            else
                local acc = get(account)
                acc.bal = (acc.bal or 0) + amount
                save()
                addLog("#" .. account .. " deposited $" .. amount)
                record("deposit", nil, account, amount)
                notify(account, "Deposited $" .. amount
                    .. ". Balance: $" .. acc.bal)
                reply = { ok = true, balance = acc.bal, label = acc.label }
            end
        elseif msg.type == "pay" then
            local to = tonumber(msg.to)
            local amount = tonumber(msg.amount)
            amount = amount and math.floor(amount)
            local from = get(id)
            if type(msg.label) == "string" and #msg.label > 0 then
                from.label = msg.label:sub(1, 12)
            end
            if not to or not amount or amount <= 0 then
                reply = { ok = false, err = "Bad payment" }
            elseif to == id then
                reply = { ok = false, err = "That's you!" }
            elseif (from.bal or 0) < amount then
                reply = { ok = false, err = "Not enough money" }
            else
                local dest = get(to)
                from.bal = from.bal - amount
                dest.bal = (dest.bal or 0) + amount
                save()
                addLog("#" .. id .. " paid #" .. to .. " $" .. amount)
                record("pay", id, to, amount)
                notify(to, "You got $" .. amount .. " from "
                    .. (from.label and (from.label .. " ") or "")
                    .. "#" .. id .. ". Balance: $" .. dest.bal)
                reply = { ok = true, balance = from.bal }
            end
        elseif msg.type == "txns" then
            if not isAdmin(id) then
                reply = { ok = false, err = "Not an admin" }
            else
                local n = math.min(#txns, tonumber(msg.limit) or 40)
                local out = {}
                for i = 1, n do out[i] = txns[i] end
                reply = { ok = true, txns = out }
            end
        elseif msg.type == "mklist" then
            reply = { ok = true, items = market.items }
        elseif msg.type == "mkpost" then
            local name = type(msg.name) == "string" and msg.name:sub(1, 20) or ""
            local price = tonumber(msg.price)
            price = price and math.floor(price)
            local desc = type(msg.desc) == "string" and msg.desc:sub(1, 60) or ""
            local mine = 0
            for _, it in ipairs(market.items) do
                if it.seller == id then mine = mine + 1 end
            end
            if name == "" or not price or price <= 0 or price > 1000000000 then
                reply = { ok = false, err = "Bad listing" }
            elseif mine >= 8 then
                reply = { ok = false, err = "Max 8 listings" }
            elseif #market.items >= 60 then
                reply = { ok = false, err = "Market is full" }
            else
                local acc = get(id)
                if type(msg.label) == "string" and #msg.label > 0 then
                    acc.label = msg.label:sub(1, 12)
                    save()
                end
                market.items[#market.items + 1] = {
                    id = market.nextId,
                    seller = id,
                    label = acc.label,
                    name = name,
                    price = price,
                    desc = desc,
                }
                market.nextId = market.nextId + 1
                saveMarket()
                addLog("#" .. id .. " listed " .. name .. " $" .. price)
                reply = { ok = true, id = market.nextId - 1 }
            end
        elseif msg.type == "mkremove" then
            local lid = tonumber(msg.id)
            local removed = false
            for k, it in ipairs(market.items) do
                if it.id == lid and it.seller == id then
                    table.remove(market.items, k)
                    removed = true
                    break
                end
            end
            if removed then
                saveMarket()
                addLog("#" .. id .. " removed a listing")
                reply = { ok = true }
            else
                reply = { ok = false, err = "Not your listing" }
            end
        end
        if reply then
            rednet.send(id, reply, "pocketos.bank")
            draw()
        end
    end
end