[project/luci.git] / libs / cbi / luasrc / cbi.lua

--[[
LuCI - Configuration Bind Interface

Description:
Offers an interface for binding configuration values to certain
data types. Supports value and range validation and basic dependencies.

FileId:
$Id$

License:
Copyright 2008 Steven Barth <steven@midlink.org>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

]]--
module("luci.cbi", package.seeall)

require("luci.template")
require("luci.util")
require("luci.http")
require("luci.uvl")

local uci        = require("luci.model.uci")
local class      = luci.util.class
local instanceof = luci.util.instanceof

FORM_NODATA  =  0
FORM_VALID   =  1
FORM_INVALID = -1

AUTO = true

CREATE_PREFIX = "cbi.cts."
REMOVE_PREFIX = "cbi.rts."

-- Loads a CBI map from given file, creating an environment and returns it
function load(cbimap, ...)
        require("luci.fs")
        local i18n = require "luci.i18n"
        require("luci.config")
        require("luci.util")

        local cbidir = luci.util.libpath() .. "/model/cbi/"
        local func, err = loadfile(cbimap) or loadfile(cbidir..cbimap..".lua")
        assert(func, err)

        luci.i18n.loadc("cbi")
        luci.i18n.loadc("uvl")

        local env = {
                translate=i18n.translate,
                translatef=i18n.translatef,
                arg={...}
        }

        setfenv(func, setmetatable(env, {__index =
                function(tbl, key)
                        return rawget(tbl, key) or _M[key] or _G[key]
                end}))

        local maps = {func()}

        for i, map in ipairs(maps) do
                if not instanceof(map, Node) then
                        error("CBI map returns no valid map object!")
                        return nil
                else
                        map:prepare()
                end
        end

        return maps
end

local function _uvl_validate_section(node, name)
        local co = node.map:get()

        luci.uvl.STRICT_UNKNOWN_OPTIONS = false
        luci.uvl.STRICT_UNKNOWN_SECTIONS = false

        local function tag_fields(e)
                if e.option and node.fields[e.option] then
                        if node.fields[e.option].error then
                                node.fields[e.option].error[name] = e
                        else
                                node.fields[e.option].error = { [name] = e }
                        end
                elseif e.childs then
                        for _, c in ipairs(e.childs) do tag_fields(c) end
                end
        end

        local function tag_section(e)
                local s = { }
                for _, c in ipairs(e.childs) do
                        if c.childs and not c:is(luci.uvl.errors.ERR_DEPENDENCY) then
                                table.insert( s, c.childs[1]:string() )
                        else
                                table.insert( s, c:string() )
                        end
                end
                if #s > 0 then
                        if node.error then
                                node.error[name] = s
                        else
                                node.error = { [name] = s }
                        end
                end
        end

        local stat, err = node.map.validator:validate_section(node.config, name, co)
        if err then
                node.map.save = false
                tag_fields(err)
                tag_section(err)
        end

end

local function _uvl_strip_remote_dependencies(deps)
        local clean = {}

        for k, v in pairs(deps) do
                k = k:gsub("%$config%.%$section%.", "")
                if k:match("^[%w_]+$") and type(v) == "string" then
                        clean[k] = v
                end
        end

        return clean
end


-- Node pseudo abstract class
Node = class()

function Node.__init__(self, title, description)
        self.children = {}
        self.title = title or ""
        self.description = description or ""
        self.template = "cbi/node"
end

-- i18n helper
function Node._i18n(self, config, section, option, title, description)

        -- i18n loaded?
        if type(luci.i18n) == "table" then

                local key = config and config:gsub("[^%w]+", "") or ""

                if section then key = key .. "_" .. section:lower():gsub("[^%w]+", "") end
                if option  then key = key .. "_" .. tostring(option):lower():gsub("[^%w]+", "")  end

                self.title = title or luci.i18n.translate( key, option or section or config )
                self.description = description or luci.i18n.translate( key .. "_desc", "" )
        end
end

-- Prepare nodes
function Node.prepare(self, ...)
        for k, child in ipairs(self.children) do
                child:prepare(...)
        end
end

-- Append child nodes
function Node.append(self, obj)
        table.insert(self.children, obj)
end

-- Parse this node and its children
function Node.parse(self, ...)
        for k, child in ipairs(self.children) do
                child:parse(...)
        end
end

-- Render this node
function Node.render(self, scope)
        scope = scope or {}
        scope.self = self

        luci.template.render(self.template, scope)
end

-- Render the children
function Node.render_children(self, ...)
        for k, node in ipairs(self.children) do
                node:render(...)
        end
end


--[[
A simple template element
]]--
Template = class(Node)

function Template.__init__(self, template)
        Node.__init__(self)
        self.template = template
end

function Template.render(self)
        luci.template.render(self.template, {self=self})
end


--[[
Map - A map describing a configuration file
]]--
Map = class(Node)

function Map.__init__(self, config, ...)
        Node.__init__(self, ...)
        Node._i18n(self, config, nil, nil, ...)

        self.config = config
        self.parsechain = {self.config}
        self.template = "cbi/map"
        self.apply_on_parse = nil
        self.uci = uci.cursor()
        self.save = true
        if not self.uci:load(self.config) then
                error("Unable to read UCI data: " .. self.config)
        end

        self.validator = luci.uvl.UVL()
        self.scheme = self.validator:get_scheme(self.config)

end

function Map.get_scheme(self, sectiontype, option)
        if not option then
                return self.scheme and self.scheme.sections[sectiontype]
        else
                return self.scheme and self.scheme.variables[sectiontype]
                 and self.scheme.variables[sectiontype][option]
        end
end


-- Chain foreign config
function Map.chain(self, config)
        table.insert(self.parsechain, config)
end

-- Use optimized UCI writing
function Map.parse(self)
        Node.parse(self)

        if self.save then
                for i, config in ipairs(self.parsechain) do
                        self.uci:save(config)
                end
                if luci.http.formvalue("cbi.apply") then
                        for i, config in ipairs(self.parsechain) do
                                self.uci:commit(config)

                                -- Refresh data because commit changes section names
                                self.uci:load(config)
                        end
                        if self.apply_on_parse then
                                self.uci:apply(self.parsechain)
                        else
                                self._apply = function()
                                        local cmd = self.uci:apply(self.parsechain, true)
                                        return io.popen(cmd)
                                end
                        end

                        -- Reparse sections
                        Node.parse(self, true)

                end
                for i, config in ipairs(self.parsechain) do
                        self.uci:unload(config)
                end
        end
end

function Map.render(self, ...)
        Node.render(self, ...)
        if self._apply then
                local fp = self._apply()
                fp:read("*a")
                fp:close()
        end
end

-- Creates a child section
function Map.section(self, class, ...)
        if instanceof(class, AbstractSection) then
                local obj  = class(self, ...)
                self:append(obj)
                return obj
        else
                error("class must be a descendent of AbstractSection")
        end
end

-- UCI add
function Map.add(self, sectiontype)
        return self.uci:add(self.config, sectiontype)
end

-- UCI set
function Map.set(self, section, option, value)
        if option then
                return self.uci:set(self.config, section, option, value)
        else
                return self.uci:set(self.config, section, value)
        end
end

-- UCI del
function Map.del(self, section, option)
        if option then
                return self.uci:delete(self.config, section, option)
        else
                return self.uci:delete(self.config, section)
        end
end

-- UCI get
function Map.get(self, section, option)
        if not section then
                return self.uci:get_all(self.config)
        elseif option then
                return self.uci:get(self.config, section, option)
        else
                return self.uci:get_all(self.config, section)
        end
end


--[[
Page - A simple node
]]--

Page = class(Node)
Page.__init__ = Node.__init__
Page.parse    = function() end


--[[
SimpleForm - A Simple non-UCI form
]]--
SimpleForm = class(Node)

function SimpleForm.__init__(self, config, title, description, data)
        Node.__init__(self, title, description)
        self.config = config
        self.data = data or {}
        self.template = "cbi/simpleform"
        self.dorender = true
end

function SimpleForm.parse(self, ...)
        if luci.http.formvalue("cbi.submit") then
                Node.parse(self, 1, ...)
        end

        local valid = true
        for k, j in ipairs(self.children) do
                for i, v in ipairs(j.children) do
                        valid = valid
                         and (not v.tag_missing or not v.tag_missing[1])
                         and (not v.tag_invalid or not v.tag_invalid[1])
                end
        end

        local state =
                not luci.http.formvalue("cbi.submit") and 0
                or valid and 1
                or -1

        self.dorender = not self.handle or self:handle(state, self.data) ~= false
end

function SimpleForm.render(self, ...)
        if self.dorender then
                Node.render(self, ...)
        end
end

function SimpleForm.section(self, class, ...)
        if instanceof(class, AbstractSection) then
                local obj  = class(self, ...)
                self:append(obj)
                return obj
        else
                error("class must be a descendent of AbstractSection")
        end
end

-- Creates a child field
function SimpleForm.field(self, class, ...)
        local section
        for k, v in ipairs(self.children) do
                if instanceof(v, SimpleSection) then
                        section = v
                        break
                end
        end
        if not section then
                section = self:section(SimpleSection)
        end

        if instanceof(class, AbstractValue) then
                local obj  = class(self, section, ...)
                obj.track_missing = true
                section:append(obj)
                return obj
        else
                error("class must be a descendent of AbstractValue")
        end
end

function SimpleForm.set(self, section, option, value)
        self.data[option] = value
end


function SimpleForm.del(self, section, option)
        self.data[option] = nil
end


function SimpleForm.get(self, section, option)
        return self.data[option]
end


function SimpleForm.get_scheme()
        return nil
end



--[[
AbstractSection
]]--
AbstractSection = class(Node)

function AbstractSection.__init__(self, map, sectiontype, ...)
        Node.__init__(self, ...)
        self.sectiontype = sectiontype
        self.map = map
        self.config = map.config
        self.optionals = {}
        self.defaults = {}
        self.fields = {}
        self.tag_error = {}
        self.tag_invalid = {}
        self.tag_deperror = {}

        self.optional = true
        self.addremove = false
        self.dynamic = false
end

-- Appends a new option
function AbstractSection.option(self, class, option, ...)
        -- Autodetect from UVL
        if class == true and self.map:get_scheme(self.sectiontype, option) then
                local vs = self.map:get_scheme(self.sectiontype, option)
                if vs.type == "boolean" then
                        class = Flag
                elseif vs.type == "list" then
                        class = DynamicList
                elseif vs.type == "enum" or vs.type == "reference" then
                        class = ListValue
                else
                        class = Value
                end
        end

        if instanceof(class, AbstractValue) then
                local obj  = class(self.map, self, option, ...)

                Node._i18n(obj, self.config, self.section or self.sectiontype, option, ...)

                self:append(obj)
                self.fields[option] = obj
                return obj
        elseif class == true then
                error("No valid class was given and autodetection failed.")
        else
                error("class must be a descendant of AbstractValue")
        end
end

-- Parse optional options
function AbstractSection.parse_optionals(self, section)
        if not self.optional then
                return
        end

        self.optionals[section] = {}

        local field = luci.http.formvalue("cbi.opt."..self.config.."."..section)
        for k,v in ipairs(self.children) do
                if v.optional and not v:cfgvalue(section) then
                        if field == v.option then
                                field = nil
                        else
                                table.insert(self.optionals[section], v)
                        end
                end
        end

        if field and #field > 0 and self.dynamic then
                self:add_dynamic(field)
        end
end

-- Add a dynamic option
function AbstractSection.add_dynamic(self, field, optional)
        local o = self:option(Value, field, field)
        o.optional = optional
end

-- Parse all dynamic options
function AbstractSection.parse_dynamic(self, section)
        if not self.dynamic then
                return
        end

        local arr  = luci.util.clone(self:cfgvalue(section))
        local form = luci.http.formvaluetable("cbid."..self.config.."."..section)
        for k, v in pairs(form) do
                arr[k] = v
        end

        for key,val in pairs(arr) do
                local create = true

                for i,c in ipairs(self.children) do
                        if c.option == key then
                                create = false
                        end
                end

                if create and key:sub(1, 1) ~= "." then
                        self:add_dynamic(key, true)
                end
        end
end

-- Returns the section's UCI table
function AbstractSection.cfgvalue(self, section)
        return self.map:get(section)
end

-- Removes the section
function AbstractSection.remove(self, section)
        return self.map:del(section)
end

-- Creates the section
function AbstractSection.create(self, section)
        local stat

        if section then
                stat = section:match("^%w+$") and self.map:set(section, nil, self.sectiontype)
        else
                section = self.map:add(self.sectiontype)
                stat = section
        end

        if stat then
                for k,v in pairs(self.children) do
                        if v.default then
                                self.map:set(section, v.option, v.default)
                        end
                end

                for k,v in pairs(self.defaults) do
                        self.map:set(section, k, v)
                end
        end

        return stat
end


SimpleSection = class(AbstractSection)

function SimpleSection.__init__(self, form, ...)
        AbstractSection.__init__(self, form, nil, ...)
        self.template = "cbi/nullsection"
end


Table = class(AbstractSection)

function Table.__init__(self, form, data, ...)
        local datasource = {}
        datasource.config = "table"
        self.data = data

        function datasource.get(self, section, option)
                return data[section] and data[section][option]
        end

        function datasource.del(...)
                return true
        end

        function datasource.get_scheme()
                return nil
        end

        AbstractSection.__init__(self, datasource, "table", ...)
        self.template = "cbi/tblsection"
        self.rowcolors = true
        self.anonymous = true
end

function Table.parse(self)
        for i, k in ipairs(self:cfgsections()) do
                if luci.http.formvalue("cbi.submit") then
                        Node.parse(self, k)
                end
        end
end

function Table.cfgsections(self)
        local sections = {}

        for i, v in luci.util.kspairs(self.data) do
                table.insert(sections, i)
        end

        return sections
end



--[[
NamedSection - A fixed configuration section defined by its name
]]--
NamedSection = class(AbstractSection)

function NamedSection.__init__(self, map, section, stype, ...)
        AbstractSection.__init__(self, map, stype, ...)
        Node._i18n(self, map.config, section, nil, ...)

        -- Defaults
        self.addremove = false

        -- Use defaults from UVL
        if not self.override_scheme and self.map:get_scheme(self.sectiontype) then
                local vs = self.map:get_scheme(self.sectiontype)
                self.addremove = not vs.unique and not vs.required
                self.dynamic   = vs.dynamic
                self.title       = self.title or vs.title
                self.description = self.description or vs.descr
        end

        self.template = "cbi/nsection"
        self.section = section
end

function NamedSection.parse(self, novld)
        local s = self.section
        local active = self:cfgvalue(s)

        if self.addremove then
                local path = self.config.."."..s
                if active then -- Remove the section
                        if luci.http.formvalue("cbi.rns."..path) and self:remove(s) then
                                return
                        end
                else           -- Create and apply default values
                        if luci.http.formvalue("cbi.cns."..path) then
                                self:create(s)
                                return
                        end
                end
        end

        if active then
                AbstractSection.parse_dynamic(self, s)
                if luci.http.formvalue("cbi.submit") then
                        Node.parse(self, s)

                        if not novld and not self.override_scheme and self.map.scheme then
                                _uvl_validate_section(self, s)
                        end
                end
                AbstractSection.parse_optionals(self, s)
        end
end


--[[
TypedSection - A (set of) configuration section(s) defined by the type
        addremove:      Defines whether the user can add/remove sections of this type
        anonymous:  Allow creating anonymous sections
        validate:       a validation function returning nil if the section is invalid
]]--
TypedSection = class(AbstractSection)

function TypedSection.__init__(self, map, type, ...)
        AbstractSection.__init__(self, map, type, ...)
        Node._i18n(self, map.config, type, nil, ...)

        self.template  = "cbi/tsection"
        self.deps = {}
        self.anonymous = false

        -- Use defaults from UVL
        if not self.override_scheme and self.map:get_scheme(self.sectiontype) then
                local vs = self.map:get_scheme(self.sectiontype)
                self.addremove = not vs.unique and not vs.required
                self.dynamic   = vs.dynamic
                self.anonymous = not vs.named
                self.title       = self.title or vs.title
                self.description = self.description or vs.descr
        end
end

-- Return all matching UCI sections for this TypedSection
function TypedSection.cfgsections(self)
        local sections = {}
        self.map.uci:foreach(self.map.config, self.sectiontype,
                function (section)
                        if self:checkscope(section[".name"]) then
                                table.insert(sections, section[".name"])
                        end
                end)

        return sections
end

-- Limits scope to sections that have certain option => value pairs
function TypedSection.depends(self, option, value)
        table.insert(self.deps, {option=option, value=value})
end

function TypedSection.parse(self, novld)
        if self.addremove then
                -- Remove
                local crval = REMOVE_PREFIX .. self.config
                local name = luci.http.formvaluetable(crval)
                for k,v in pairs(name) do
                        if k:sub(-2) == ".x" then
                                k = k:sub(1, #k - 2)
                        end
                        if self:cfgvalue(k) and self:checkscope(k) then
                                self:remove(k)
                        end
                end
        end

        local co
        for i, k in ipairs(self:cfgsections()) do
                AbstractSection.parse_dynamic(self, k)
                if luci.http.formvalue("cbi.submit") then
                        Node.parse(self, k)

                        if not novld and not self.override_scheme and self.map.scheme then
                                _uvl_validate_section(self, k)
                        end
                end
                AbstractSection.parse_optionals(self, k)
        end

        if self.addremove then
                -- Create
                local created
                local crval = CREATE_PREFIX .. self.config .. "." .. self.sectiontype
                local name  = luci.http.formvalue(crval)
                if self.anonymous then
                        if name then
                                created = self:create()
                        end
                else
                        if name then
                                -- Ignore if it already exists
                                if self:cfgvalue(name) then
                                        name = nil;
                                end

                                name = self:checkscope(name)

                                if not name then
                                        self.err_invalid = true
                                end

                                if name and #name > 0 then
                                        created = self:create(name) and name
                                        if not created then
                                                self.invalid_cts = true
                                        end
                                end
                        end
                end

                if created then
                        AbstractSection.parse_optionals(self, created)
                end
        end
end

-- Verifies scope of sections
function TypedSection.checkscope(self, section)
        -- Check if we are not excluded
        if self.filter and not self:filter(section) then
                return nil
        end

        -- Check if at least one dependency is met
        if #self.deps > 0 and self:cfgvalue(section) then
                local stat = false

                for k, v in ipairs(self.deps) do
                        if self:cfgvalue(section)[v.option] == v.value then
                                stat = true
                        end
                end

                if not stat then
                        return nil
                end
        end

        return self:validate(section)
end


-- Dummy validate function
function TypedSection.validate(self, section)
        return section
end


--[[
AbstractValue - An abstract Value Type
        null:           Value can be empty
        valid:          A function returning the value if it is valid otherwise nil
        depends:        A table of option => value pairs of which one must be true
        default:        The default value
        size:           The size of the input fields
        rmempty:        Unset value if empty
        optional:       This value is optional (see AbstractSection.optionals)
]]--
AbstractValue = class(Node)

function AbstractValue.__init__(self, map, section, option, ...)
        Node.__init__(self, ...)
        self.section = section
        self.option  = option
        self.map     = map
        self.config  = map.config
        self.tag_invalid = {}
        self.tag_missing = {}
        self.tag_reqerror = {}
        self.tag_error = {}
        self.deps = {}
        --self.cast = "string"

        self.track_missing = false
        --self.rmempty   = false
        self.default   = nil
        self.size      = nil
        self.optional  = false
end

function AbstractValue.prepare(self)
        -- Use defaults from UVL
        if not self.override_scheme
         and self.map:get_scheme(self.section.sectiontype, self.option) then
                local vs = self.map:get_scheme(self.section.sectiontype, self.option)
                if self.rmempty == nil then
                        self.rmempty = not vs.required
                end
                if self.cast == nil then
                        self.cast = (vs.type == "list") and "list" or "string"
                end
                self.title       = self.title or vs.title
                self.description = self.description or vs.descr
                if self.default == nil then
                        self.default = vs.default
                end

                if vs.depends and not self.override_dependencies then
                        for i, deps in ipairs(vs.depends) do
                                deps = _uvl_strip_remote_dependencies(deps)
                                if next(deps) then
                                        self:depends(deps)
                                end
                        end
                end
        end

        self.cast = self.cast or "string"
end

-- Add a dependencie to another section field
function AbstractValue.depends(self, field, value)
        local deps
        if type(field) == "string" then
                deps = {}
                deps[field] = value
        else
                deps = field
        end

        table.insert(self.deps, {deps=deps, add=""})
end

-- Generates the unique CBID
function AbstractValue.cbid(self, section)
        return "cbid."..self.map.config.."."..section.."."..self.option
end

-- Return whether this object should be created
function AbstractValue.formcreated(self, section)
        local key = "cbi.opt."..self.config.."."..section
        return (luci.http.formvalue(key) == self.option)
end

-- Returns the formvalue for this object
function AbstractValue.formvalue(self, section)
        return luci.http.formvalue(self:cbid(section))
end

function AbstractValue.additional(self, value)
        self.optional = value
end

function AbstractValue.mandatory(self, value)
        self.rmempty = not value
end

function AbstractValue.parse(self, section)
        local fvalue = self:formvalue(section)
        local cvalue = self:cfgvalue(section)

        if fvalue and #fvalue > 0 then -- If we have a form value, write it to UCI
                fvalue = self:transform(self:validate(fvalue, section))
                if not fvalue then
                        self.tag_invalid[section] = true
                end
                if fvalue and not (fvalue == cvalue) then
                        self:write(section, fvalue)
                end
        else                                                    -- Unset the UCI or error
                if self.rmempty or self.optional then
                        self:remove(section)
                elseif self.track_missing and (not fvalue or fvalue ~= cvalue) then
                        self.tag_missing[section] = true
                end
        end
end

-- Render if this value exists or if it is mandatory
function AbstractValue.render(self, s, scope)
        if not self.optional or self:cfgvalue(s) or self:formcreated(s) then
                scope = scope or {}
                scope.section   = s
                scope.cbid      = self:cbid(s)
                scope.striptags = luci.util.striptags

                scope.ifattr = function(cond,key,val)
                        if cond then
                                return string.format(
                                        ' %s="%s"', tostring(key),
                                        luci.util.pcdata(tostring( val
                                         or scope[key]
                                         or (type(self[key]) ~= "function" and self[key])
                                         or "" ))
                                )
                        else
                                return ''
                        end
                end

                scope.attr = function(...)
                        return scope.ifattr( true, ... )
                end

                Node.render(self, scope)
        end
end

-- Return the UCI value of this object
function AbstractValue.cfgvalue(self, section)
        local value = self.map:get(section, self.option)
        if not value then
                return nil
        elseif not self.cast or self.cast == type(value) then
                return value
        elseif self.cast == "string" then
                if type(value) == "table" then
                        return value[1]
                end
        elseif self.cast == "table" then
                return luci.util.split(value, "%s+", nil, true)
        end
end

-- Validate the form value
function AbstractValue.validate(self, value)
        return value
end

AbstractValue.transform = AbstractValue.validate


-- Write to UCI
function AbstractValue.write(self, section, value)
        return self.map:set(section, self.option, value)
end

-- Remove from UCI
function AbstractValue.remove(self, section)
        return self.map:del(section, self.option)
end




--[[
Value - A one-line value
        maxlength:      The maximum length
]]--
Value = class(AbstractValue)

function Value.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/value"
        self.keylist = {}
        self.vallist = {}
end

function Value.value(self, key, val)
        val = val or key
        table.insert(self.keylist, tostring(key))
        table.insert(self.vallist, tostring(val))
end


-- DummyValue - This does nothing except being there
DummyValue = class(AbstractValue)

function DummyValue.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template = "cbi/dvalue"
        self.value = nil
end

function DummyValue.cfgvalue(self, section)
        local value
        if self.value then
                if type(self.value) == "function" then
                        value = self:value(section)
                else
                        value = self.value
                end
        else
                value = AbstractValue.cfgvalue(self, section)
        end
        return value
end

function DummyValue.parse(self)

end


--[[
Flag - A flag being enabled or disabled
]]--
Flag = class(AbstractValue)

function Flag.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/fvalue"

        self.enabled = "1"
        self.disabled = "0"
end

-- A flag can only have two states: set or unset
function Flag.parse(self, section)
        local fvalue = self:formvalue(section)

        if fvalue then
                fvalue = self.enabled
        else
                fvalue = self.disabled
        end

        if fvalue == self.enabled or (not self.optional and not self.rmempty) then
                if not(fvalue == self:cfgvalue(section)) then
                        self:write(section, fvalue)
                end
        else
                self:remove(section)
        end
end



--[[
ListValue - A one-line value predefined in a list
        widget: The widget that will be used (select, radio)
]]--
ListValue = class(AbstractValue)

function ListValue.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/lvalue"

        self.keylist = {}
        self.vallist = {}
        self.size   = 1
        self.widget = "select"
end

function ListValue.prepare(self, ...)
        AbstractValue.prepare(self, ...)
        if not self.override_scheme
         and self.map:get_scheme(self.section.sectiontype, self.option) then
                local vs = self.map:get_scheme(self.section.sectiontype, self.option)
                if self.value and vs.valuelist and not self.override_values then
                        for k, v in ipairs(vs.valuelist) do
                                local deps = {}
                                if not self.override_dependencies
                                 and vs.enum_depends and vs.enum_depends[v.value] then
                                        for i, dep in ipairs(vs.enum_depends[v.value]) do
                                                table.insert(deps, _uvl_strip_remote_dependencies(dep))
                                        end
                                end
                                self:value(v.value, v.title or v.value, unpack(deps))
                        end
                end
        end
end

function ListValue.value(self, key, val, ...)
        if luci.util.contains(self.keylist, key) then
                return
        end

        val = val or key
        table.insert(self.keylist, tostring(key))
        table.insert(self.vallist, tostring(val))

        for i, deps in ipairs({...}) do
                table.insert(self.deps, {add = "-"..key, deps=deps})
        end
end

function ListValue.validate(self, val)
        if luci.util.contains(self.keylist, val) then
                return val
        else
                return nil
        end
end



--[[
MultiValue - Multiple delimited values
        widget: The widget that will be used (select, checkbox)
        delimiter: The delimiter that will separate the values (default: " ")
]]--
MultiValue = class(AbstractValue)

function MultiValue.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template = "cbi/mvalue"

        self.keylist = {}
        self.vallist = {}

        self.widget = "checkbox"
        self.delimiter = " "
end

function MultiValue.render(self, ...)
        if self.widget == "select" and not self.size then
                self.size = #self.vallist
        end

        AbstractValue.render(self, ...)
end

function MultiValue.value(self, key, val)
        if luci.util.contains(self.keylist, key) then
                return
        end

        val = val or key
        table.insert(self.keylist, tostring(key))
        table.insert(self.vallist, tostring(val))
end

function MultiValue.valuelist(self, section)
        local val = self:cfgvalue(section)

        if not(type(val) == "string") then
                return {}
        end

        return luci.util.split(val, self.delimiter)
end

function MultiValue.validate(self, val)
        val = (type(val) == "table") and val or {val}

        local result

        for i, value in ipairs(val) do
                if luci.util.contains(self.keylist, value) then
                        result = result and (result .. self.delimiter .. value) or value
                end
        end

        return result
end


StaticList = class(MultiValue)

function StaticList.__init__(self, ...)
        MultiValue.__init__(self, ...)
        self.cast = "table"
        self.valuelist = self.cfgvalue

        if not self.override_scheme
         and self.map:get_scheme(self.section.sectiontype, self.option) then
                local vs = self.map:get_scheme(self.section.sectiontype, self.option)
                if self.value and vs.values and not self.override_values then
                        for k, v in pairs(vs.values) do
                                self:value(k, v)
                        end
                end
        end
end

function StaticList.validate(self, value)
        value = (type(value) == "table") and value or {value}

        local valid = {}
        for i, v in ipairs(value) do
                if luci.util.contains(self.vallist, v) then
                        table.insert(valid, v)
                end
        end
        return valid
end


DynamicList = class(AbstractValue)

function DynamicList.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/dynlist"
        self.cast = "table"
        self.keylist = {}
        self.vallist = {}
end

function DynamicList.value(self, key, val)
        val = val or key
        table.insert(self.keylist, tostring(key))
        table.insert(self.vallist, tostring(val))
end

function DynamicList.formvalue(self, section)
        local value = AbstractValue.formvalue(self, section)
        value = (type(value) == "table") and value or {value}

        local valid = {}
        for i, v in ipairs(value) do
                if v and #v > 0
                 and not luci.http.formvalue("cbi.rle."..section.."."..self.option.."."..i)
                 and not luci.http.formvalue("cbi.rle."..section.."."..self.option.."."..i..".x") then
                        table.insert(valid, v)
                end
        end

        return valid
end


--[[
TextValue - A multi-line value
        rows:   Rows
]]--
TextValue = class(AbstractValue)

function TextValue.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/tvalue"
end

--[[
Button
]]--
Button = class(AbstractValue)

function Button.__init__(self, ...)
        AbstractValue.__init__(self, ...)
        self.template  = "cbi/button"
        self.inputstyle = nil
        self.rmempty = true
end