--- For working with mod configurations.
-- @module Config
-- @usage require('stdlib/config/config')

---
-- @tfield function new
-- @tfield function get
-- @tfield function set
-- @tfield function delete
-- @tfield function is_set
-- @table Config
local M = {_module = 'Config'}
setmetatable(M, require('stdlib/core'))

-----------------------------------------------------------------------
--Setup repeated code for use in sub functions here
-----------------------------------------------------------------------
local reservedCharacters = [[`~!@#$%^&*+=|;:/\\\'",?()[]{}<>]]
local testReservedCharacters = function(path)
    local reserved = reservedCharacters
    for c in reserved:gmatch('.') do
        if path:find(c, 1, true) then
            return c
        end
    end
    return nil
end

--- Creates a new Config object to ease the management of a config table.
-- @tparam table config_table the config table to manage
-- @treturn Config the Config object to manage the config table
--
-- @usage --[Use a global table for config that persists across game save/loads]
-- CONFIG = Config.new(global.testtable)
--
-- @usage --[You can also create a temporary scratch pad config]
-- CONFIG = Config.new({}) -- Temporary scratch pad
--
-- @usage --[Setting data in Config]
-- CONFIG = Config.new(global.testtable)
-- CONFIG.set("your.path.here", "myvalue")
--
-- @usage --[Getting data out of Config]
-- CONFIG = Config.new(global.testtable)
-- my_data = CONFIG.get("your.path.here")
--
-- @usage --[Getting data out of Config with a default to use if path is not found in Config]
-- CONFIG = Config.new(global.testtable)
-- my_data = CONFIG.get("your.path.here", "Your Default here")
--
-- @usage --[Deleting a path from Config]
-- CONFIG = Config.new(global.testtable)
-- CONFIG.delete("your.path.here")
--
-- @usage --[Checking if a path exists in Config]
-- CONFIG = Config.new(global.testtable)
-- CONFIG.is_set("your.path.here")
function M.new(config_table)
    if not config_table then
        error('config_table is a required parameter.', 2)
    elseif type(config_table) ~= 'table' then
        error('config_table must be a table. Was given [' .. type(config_table) .. ']', 2)
    elseif type(config_table.get) == 'function' then
        error("Config can't manage another Config object", 2)
    end

    -----------------------------------------------------------------------
    --Setup the Config object
    -----------------------------------------------------------------------
    local Config = {}

    --- Get a stored config value.
    -- @tparam string path the variable to retrieve
    -- @tparam[opt] Mixed default value to be used if path is nil
    -- @treturn Mixed value at path or nil if not found and no default given
    function Config.get(path, default)
        if type(path) ~= 'string' or path:is_empty() then
            error('path is invalid', 2)
        end

        local config = config_table

        local c = testReservedCharacters(path)
        if c ~= nil then
            error("path '" .. path .. "' contains the reserved character '" .. c .. "'", 2)
        end

        local pathParts = path:split('.')
        local part = config
        local value = nil

        for key = 1, #pathParts, 1 do
            local partKey = pathParts[key]
            if (type(part) ~= 'table') then
                value = nil
                break
            end

            value = part[partKey]
            part = part[partKey]
        end

        if (type(value) == 'table') then
            --Force break references.
            return table.deepcopy(value)
        elseif (value ~= nil) then
            return value
        else
            return default
        end
    end

    --- Set a stored config value.
    -- @tparam string path the config path to set
    -- @tparam ?|nil|Mixed data the value to set the path to. If *nil*, it behaves identical to @{delete|Config.delete()}
    -- @treturn uint 0 on failure or the number of affected paths on success
    function Config.set(path, data)
        if type(path) ~= 'string' or path:is_empty() then
            error('path is invalid', 2)
        end

        local config = config_table

        local c = testReservedCharacters(path)
        if c ~= nil then
            error("path contains the reserved character '" .. c .. "'", 2)
        end

        local pathParts = path:split('.')
        local part = config

        for key = 1, #pathParts - 1, 1 do
            local partKey = pathParts[key]
            if (type(part[partKey]) ~= 'table') then
                part[partKey] = {}
            end

            part = part[partKey]
        end

        part[pathParts[#pathParts]] = data

        return 1
    end

    --- Delete a stored config value.
    -- @tparam string path the config path to delete
    -- @treturn uint 0 on failure or the number of affected paths on success
    function Config.delete(path)
        if type(path) ~= 'string' or path:is_empty() then
            error('path is invalid', 2)
        end

        local config = config_table

        local c = testReservedCharacters(path)
        if c ~= nil then
            error("path contains the reserved character '" .. c .. "'", 2)
        end

        local pathParts = path:split('.')
        local part = config

        for key = 1, #pathParts - 1, 1 do
            local partKey = pathParts[key]
            if (type(part[partKey]) ~= 'table') then
                return 0
            end

            part = part[partKey]
        end

        if part[pathParts[#pathParts]] == nil then
            return 0
        else
            part[pathParts[#pathParts]] = nil
            return 1
        end
    end

    --- Test the existence of a stored config value.
    -- @tparam string path the config path to test
    -- @treturn boolean true if the value exists, false otherwise
    function Config.is_set(path)
        if type(path) ~= 'string' or path:is_empty() then
            error('path is invalid', 2)
        end

        return Config.get(path) ~= nil
    end

    return Config
end

return M
