--[[
    Core API and Data Handling
    --------------------------
    This file manages all low-level reading from and writing to the 'accounts' data file.
    It provides a safe and centralized API for all other mod files to interact with player data.
--]]

local world_path = minetest.get_worldpath()
local file_path = world_path .. "/accounts"

-- Normalizes a string to use '.' as a decimal separator and converts to a number.
-- Handles both "1,23" and "1.23".
function normalize_and_tonumber(str)
    if not str then
        return nil
    end
    str = str:gsub(",", ".")
    return tonumber(str)
end

-- Internal function to read the entire accounts database file.
-- Returns a populated table or a clean default structure on any error.
local function read_accounts_file()
    local f = io.open(file_path, "r")
    if not f then
        return { balance = {}, pin = {}, credit = {}, history = {} }
    end
    local data = f:read("*a")
    f:close()
    if data == "" or data == nil then
        return { balance = {}, pin = {}, credit = {}, history = {} }
    end
    return minetest.deserialize(data) or { balance = {}, pin = {}, credit = {}, history = {} }
end

-- Internal function to write the entire accounts database file.
-- Includes a locking mechanism to prevent race conditions with the interest script.
local function save_accounts_file(data)
    -- If the daily interest calculation is running, wait in short intervals until it's done.
    while bank_accounts and bank_accounts.is_calculating_interest do
        minetest.log("action", "[bank_accounts] Interest calculation in progress, delaying save operation...")
        minetest.sleep(0.5)
    end

    local f, err = io.open(file_path, "w")
    if not f then
        minetest.log("error", "[bank_accounts] Could not open accounts file for writing: " .. tostring(err))
        return false
    end
    f:write(minetest.serialize(data))
    f:close()
    return true
end

-- Internal function to log a single transaction to a player's history.
local function log_transaction(data, player_name, account_type, amount, new_total, trans_type, purpose, other_party)
    -- Ensure history tables exist.
    if not data.history then data.history = {} end
    if not data.history[player_name] then data.history[player_name] = {} end

    local transaction = {
        timestamp = os.time(),
        type = trans_type or "unknown",
        account = account_type, -- "balance" or "credit"
        amount = amount,
        new_total = new_total,
        purpose = purpose or "", -- e.g., "Teller: Rage87" or user-defined text
        other = other_party or ""   -- e.g., recipient or sender name
    }
    -- Insert at the beginning of the list to show newest transactions first.
    table.insert(data.history[player_name], 1, transaction)

    -- Limit history to the last 200 entries to prevent the file from growing indefinitely.
    while #data.history[player_name] > 200 do
        table.remove(data.history[player_name])
    end
end

-- On server start, create the accounts file if it doesn't exist.
do
    local f = io.open(file_path, "r")
    if not f then
        save_accounts_file({ balance = {}, pin = {}, credit = {}, history = {} })
    else
        f:close()
    end
end

---------------------------------------------------
-- Public API accessible via `bank_accounts.*`
---------------------------------------------------

-- Gets all relevant data for a single player.
function bank_accounts.get_account_data(player_name)
    local data = read_accounts_file()
    -- Backwards compatibility check for old save files without a history table.
    if not data.history then
        data.history = {}
    end
    return {
        balance = data.balance[player_name] or 0,
        pin = data.pin[player_name] or "0000",
        credit = data.credit[player_name] or 0,
        history = data.history[player_name] or {},
    }
end

-- Gets all data from the database (for background scripts like interest calculation).
function bank_accounts.get_all_data()
    return read_accounts_file()
end

-- Saves the complete data object (for background scripts).
function bank_accounts.save_all(data)
    return save_accounts_file(data)
end

-- Simple getter functions.
function bank_accounts.get_balance(player_name) local data = read_accounts_file(); return data.balance[player_name] or 0 end
function bank_accounts.get_credit(player_name) local data = read_accounts_file(); return data.credit[player_name] or 0 end
function bank_accounts.get_pin(player_name) local data = read_accounts_file(); return data.pin[player_name] or "0000" end

-- Adds a value to a player's balance and logs the transaction.
function bank_accounts.add_balance(player_name, amount, trans_type, purpose, other_party)
    local data = read_accounts_file()
    local current_balance = data.balance[player_name] or 0
    local new_balance = current_balance + tonumber(amount)
    data.balance[player_name] = new_balance
    log_transaction(data, player_name, "balance", amount, new_balance, trans_type, purpose, other_party)
    return save_accounts_file(data)
end

-- Sets a player's balance to an absolute value and logs the transaction.
function bank_accounts.set_balance(player_name, amount, trans_type, purpose, other_party)
    local data = read_accounts_file()
    local current_balance = data.balance[player_name] or 0
    local new_balance = tonumber(amount)
    local diff = new_balance - current_balance
    data.balance[player_name] = new_balance
    log_transaction(data, player_name, "balance", diff, new_balance, trans_type or "admin_set", purpose, other_party)
    return save_accounts_file(data)
end

-- Adds a value to a player's credit debt and logs the transaction.
function bank_accounts.add_credit(player_name, amount, trans_type, purpose, other_party)
    local data = read_accounts_file()
    local current_credit = data.credit[player_name] or 0
    local new_credit = current_credit + tonumber(amount)
    data.credit[player_name] = new_credit
    log_transaction(data, player_name, "credit", amount, new_credit, trans_type, purpose, other_party)
    return save_accounts_file(data)
end

-- Sets a player's credit debt to an absolute value and logs the transaction.
function bank_accounts.set_credit(player_name, amount, trans_type, purpose, other_party)
    local data = read_accounts_file()
    local current_credit = data.credit[player_name] or 0
    local new_credit = tonumber(amount)
    local diff = new_credit - current_credit
    data.credit[player_name] = new_credit
    log_transaction(data, player_name, "credit", diff, new_credit, trans_type or "admin_set_credit", purpose, other_party)
    return save_accounts_file(data)
end

-- Sets a player's PIN.
function bank_accounts.set_pin(player_name, pin)
    local data = read_accounts_file()
    data.pin[player_name] = tostring(pin)
    return save_accounts_file(data)
end

-- Checks if a player has an entry in the database.
function bank_accounts.player_has_account(player_name)
    local data = read_accounts_file()
    return data.balance[player_name] ~= nil
end

-- Creates a new, empty account for a player.
function bank_accounts.create_account(player_name)
    if bank_accounts.player_has_account(player_name) then
        return false
    end
    local data = read_accounts_file()
    data.balance[player_name] = 0
    data.pin[player_name] = "0000"
    data.credit[player_name] = 0
    if not data.history then
        data.history = {}
    end
    data.history[player_name] = {}
    log_transaction(data, player_name, "system", 0, 0, "Account Created", "Initial account setup")
    return save_accounts_file(data)
end