root/ff-luci/trunk/libs/uvl/luasrc/uvl.lua @ 2972

--[[

UCI Validation Layer - Main Library
(c) 2008 Jo-Philipp Wich <xm@leipzig.freifunk.net>
(c) 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

$Id$

]]--


--- UVL - UCI Validation Layer
-- @class   module
-- @cstyle  instance

module( "luci.uvl", package.seeall )

require("luci.fs")
require("luci.util")
require("luci.model.uci")
require("luci.uvl.errors")
require("luci.uvl.datatypes")
require("luci.uvl.validation")
require("luci.uvl.dependencies")


TYPE_SCHEME   = 0x00
TYPE_CONFIG   = 0x01
TYPE_SECTION  = 0x02
TYPE_VARIABLE = 0x03
TYPE_OPTION   = 0x04
TYPE_ENUM     = 0x05

--- Boolean; default true;
-- treat sections found in config but not in scheme as error
STRICT_UNKNOWN_SECTIONS    = true

--- Boolean; default true;
-- treat options found in config but not in scheme as error
STRICT_UNKNOWN_OPTIONS     = true

--- Boolean; default true;
-- treat failed external validators as error
STRICT_EXTERNAL_VALIDATORS = true

--- Boolean; default true;
-- treat list values stored as options like errors
STRICT_LIST_TYPE           = true


local default_schemedir = "/lib/uci/schema"
local ERR = luci.uvl.errors


--- Object constructor
-- @class           function
-- @name            UVL
-- @param schemedir Path to the scheme directory (optional)
-- @return          Instance object
UVL = luci.util.class()

function UVL.__init__( self, schemedir )
    self.schemedir  = schemedir or default_schemedir
    self.packages   = { }
    self.beenthere  = { }
    self.uci        = luci.model.uci
    self.err        = luci.uvl.errors
    self.dep        = luci.uvl.dependencies
    self.datatypes  = luci.uvl.datatypes
end


--- Parse given scheme and return the scheme tree.
-- @param scheme    Name of the scheme to parse
-- @return          Table containing the parsed scheme or nil on error
-- @return          String containing the reason for errors (if any)
function UVL.get_scheme( self, scheme )
    if not self.packages[scheme] then
        local ok, err = self:read_scheme( scheme )
        if not ok then
            return nil, err
        end
    end
    return self.packages[scheme], nil
end

--- Validate given configuration, section or option.
-- @param config    Name of the configuration to validate
-- @param section   Name of the section to validate (optional)
-- @param option    Name of the option to validate (optional)
-- @return          Boolean indicating whether the given config validates
-- @return          String containing the reason for errors (if any)
function UVL.validate( self, config, section, option )
    if config and section and option then
        return self:validate_option( config, section, option )
    elseif config and section then
        return self:validate_section( config, section )
    elseif config then
        return self:validate_config( config )
    end
end

--- Validate given configuration.
-- @param config    Name of the configuration to validate
-- @return          Boolean indicating whether the given config validates
-- @return          String containing the reason for errors (if any)
function UVL.validate_config( self, config )

    if not self.packages[config] then
        local ok, err = self:read_scheme(config)
        if not ok then
            return false, err
        end
    end

    local co = luci.uvl.config( self, config )
    local sc = { }

    self.beenthere = { }

    if not co:config() then
        return false, ERR.UCILOAD(co)
    end

    local function _uci_foreach( type, func )
        for k, v in pairs(co:config()) do
            if v['.type'] == type then
                sc[type] = sc[type] + 1
                local ok, err = func( k, v )
                if not ok then co:error(err) end
            end
        end
    end

    for k, v in pairs( self.packages[config].sections ) do
        sc[k] = 0
        _uci_foreach( k,
            function(s)
                return self:_validate_section( co:section(s) )
            end
        )
    end

    if STRICT_UNKNOWN_SECTIONS then
        for k, v in pairs(co:config()) do
            local so = co:section(k)
            if not self.beenthere[so:cid()] then
                co:error(ERR.SECT_UNKNOWN(so))
            end
        end
    end

    for _, k in ipairs(luci.util.keys(sc)) do
        local so = co:section(k)
        if so:scheme('required') and sc[k] == 0 then
            co:error(ERR.SECT_REQUIRED(so))
        elseif so:scheme('unique') and sc[k] > 1 then
            co:error(ERR.SECT_UNIQUE(so))
        end
    end

    return co:ok(), co:errors()
end

--- Validate given config section.
-- @param config    Name of the configuration to validate
-- @param section   Name of the section to validate
-- @return          Boolean indicating whether the given config validates
-- @return          String containing the reason for errors (if any)
function UVL.validate_section( self, config, section )

    if not self.packages[config] then
        local ok, err = self:read_scheme( config )
        if not ok then
            return false, err
        end
    end

    local co = luci.uvl.config( self, config )
    local so = co:section( section )

    self.beenthere = { }

    if not co:config() then
        return false, ERR.UCILOAD(co)
    end

    if so:config() then
        return self:_validate_section( so )
    else
        return false, ERR.SECT_NOTFOUND(so)
    end
end

--- Validate given config option.
-- @param config    Name of the configuration to validate
-- @param section   Name of the section to validate
-- @param option    Name of the option to validate
-- @return          Boolean indicating whether the given config validates
-- @return          String containing the reason for errors (if any)
function UVL.validate_option( self, config, section, option )

    if not self.packages[config] then
        local ok, err = self:read_scheme( config )
        if not ok then
            return false, err
        end
    end

    local co = luci.uvl.config( self, config )
    local so = co:section( section )
    local oo = so:option( option )

    if not co then
        return false, oerr:child(ERR.UCILOAD(config))
    end

    if so:config() and oo:config() then
        return self:_validate_option( oo )
    else
        return false, ERR.OPT_NOTFOUND(oo)
    end
end


function UVL._validate_section( self, section )

    if section:config() then
        if section:scheme('named') == true and
           section:config('.anonymous') == true
        then
            return false, ERR.SECT_NAMED(section)
        end

        for _, v in ipairs(section:variables()) do
            local ok, err = self:_validate_option( v )
            if not ok then
                section:error(err)
            end
        end

        local ok, err = luci.uvl.dependencies.check( self, section )
        if not ok then
            section:error(err)
        end
    else
        return false, ERR.SECT_NOTFOUND(section)
    end

    if STRICT_UNKNOWN_OPTIONS and not section:scheme('dynamic') then
        for k, v in pairs(section:config()) do
            local oo = section:option(k)
            if k:sub(1,1) ~= "." and not self.beenthere[oo:cid()] then
                section:error(ERR.OPT_NOTFOUND(oo))
            end
        end
    end

    return section:ok(), section:errors()
end

function UVL._validate_option( self, option, nodeps )

    if not option:scheme() and not option:parent():scheme('dynamic') then
        return false, option:error(ERR.OPT_UNKNOWN(option))

    elseif option:scheme() then
        if option:scheme('required') and not option:value() then
            return false, option:error(ERR.OPT_REQUIRED(option))

        elseif option:value() then
            local val = option:value()

            if option:scheme('type') == "reference" or
               option:scheme('type') == "enum"
            then
                if not option:scheme('values') or
                   not option:scheme('values')[val]
                then
                    return false, option:error( ERR.OPT_BADVALUE(
                        option, { val, table.concat(
                            luci.util.keys(option:scheme('values') or {}), ", "
                        ) }
                    ) )
                end
            elseif option:scheme('type') == "list" then
                if type(val) ~= "table" and STRICT_LIST_TYPE then
                    return false, option:error(ERR.OPT_NOTLIST(option))
                end
            elseif option:scheme('datatype') then
                local dt = option:scheme('datatype')

                if self.datatypes[dt] then
                    val = ( type(val) == "table" and val or { val } )
                    for i, v in ipairs(val) do
                        if not self.datatypes[dt]( v ) then
                            return false, option:error(
                                ERR.OPT_INVVALUE(option, {v, dt})
                            )
                        end
                    end
                else
                    return false, option:error(ERR.OPT_DATATYPE(option, dt))
                end
            end
        end

        if not nodeps then
            local ok, err = luci.uvl.dependencies.check( self, option )
            if not ok then
                option:error(err)
            end
        end

        local ok, err = luci.uvl.validation.check( self, option )
        if not ok and STRICT_EXTERNAL_VALIDATORS then
            return false, option:error(err)
        end
    end

    return option:ok(), option:errors()
end

--- Find all parts of given scheme and construct validation tree.
-- This is normally done on demand, so you don't have to call this function
-- by yourself.
-- @param scheme    Name of the scheme to parse
function UVL.read_scheme( self, scheme )

    local so = luci.uvl.scheme( self, scheme )

    local schemes = { }
    local files = luci.fs.glob(self.schemedir .. '/*/' .. scheme)

    if files then
        for i, file in ipairs( files ) do
            if not luci.fs.access(file) then
                return so:error(ERR.SME_READ(so,file))
            end

            local uci = luci.model.uci.cursor()
                  uci:set_confdir( luci.fs.dirname(file) )

            local sd = uci:get_all( luci.fs.basename(file) )

            if not sd then
                return false, ERR.UCILOAD(so)
            end

            table.insert( schemes, sd )
        end

        return self:_read_scheme_parts( so, schemes )
    else
        return false, so:error(ERR.SME_FIND(so, self.schemedir))
    end
end

-- Process all given parts and construct validation tree
function UVL._read_scheme_parts( self, scheme, schemes )

    -- helper function to check for required fields
    local function _req( c, t, r )
        for i, v in ipairs(r) do
            if not t[v] then
                return false, ERR.SME_REQFLD({c,t}, v)
            end
        end
        return true
    end

    -- helper function to validate references
    local function _ref( c, t )
        local k, n
        if c == TYPE_SECTION then
            k = "package"
            n = 1
        elseif c == TYPE_VARIABLE then
            k = "section"
            n = 2
        elseif c == TYPE_ENUM then
            k = "variable"
            n = 3
        end

        local r = luci.util.split( t[k], "." )
        r[1] = ( #r[1] > 0 and r[1] or scheme:sid() )

        if #r ~= n then
            return false, ERR.SME_BADREF(scheme, k)
        end

        return r
    end

    -- helper function to read bools
    local function _bool( v )
        return ( v == "true" or v == "yes" or v == "on" or v == "1" )
    end


    local ok, err

    -- Step 1: get all sections
    for i, conf in ipairs( schemes ) do
        for k, v in pairs( conf ) do
            if v['.type'] == 'section' then

                ok, err = _req( TYPE_SECTION, v, { "name", "package" } )
                if err then return false, scheme:error(err) end

                local r, err = _ref( TYPE_SECTION, v )
                if err then return false, scheme:error(err) end

                self.packages[r[1]] =
                    self.packages[r[1]] or {
                        ["name"]      = r[1];
                        ["sections"]  = { };
                        ["variables"] = { };
                    }

                local p = self.packages[r[1]]
                      p.sections[v.name]  = p.sections[v.name]  or { }
                      p.variables[v.name] = p.variables[v.name] or { }

                local s  = p.sections[v.name]
                local so = scheme:section(v.name)

                for k, v2 in pairs(v) do
                    if k ~= "name" and k ~= "package" and k:sub(1,1) ~= "." then
                        if k == "depends" then
                            s.depends = self:_read_dependency( v2, s.depends )
                            if not s.depends then
                                return false, scheme:error(
                                    ERR.SME_BADDEP(so, luci.util.serialize_data(s.depends))
                                )
                            end
                        elseif k == "dynamic" or k == "unique" or
                               k == "required" or k == "named"
                        then
                            s[k] = _bool(v2)
                        else
                            s[k] = v2
                        end
                    end
                end

                s.dynamic  = s.dynamic  or false
                s.unique   = s.unique   or false
                s.required = s.required or false
                s.named    = s.named    or false
            end
        end
    end

    -- Step 2: get all variables
    for i, conf in ipairs( schemes ) do
        for k, v in pairs( conf ) do
            if v['.type'] == "variable" then

                ok, err = _req( TYPE_VARIABLE, v, { "name", "section" } )
                if err then return false, scheme:error(err) end

                local r, err = _ref( TYPE_VARIABLE, v )
                if err then return false, scheme:error(err) end

                local p = self.packages[r[1]]
                if not p then
                    return false, scheme:error(
                        ERR.SME_VBADPACK({scheme:sid(), '', v.name}, r[1])
                    )
                end

                local s = p.variables[r[2]]
                if not s then
                    return false, scheme:error(
                        ERR.SME_VBADSECT({scheme:sid(), '', v.name}, r[2])
                    )
                end

                s[v.name] = s[v.name] or { }

                local t  = s[v.name]
                local so = scheme:section(r[2])
                local to = so:option(v.name)

                for k, v2 in pairs(v) do
                    if k ~= "name" and k ~= "section" and k:sub(1,1) ~= "." then
                        if k == "depends" then
                            t.depends = self:_read_dependency( v2, t.depends )
                            if not t.depends then
                                return false, scheme:error(so:error(
                                    ERR.SME_BADDEP(to, luci.util.serialize_data(v2))
                                ))
                            end
                        elseif k == "validator" then
                            t.validators = self:_read_validator( v2, t.validators )
                            if not t.validators then
                                return false, scheme:error(so:error(
                                    ERR.SME_BADVAL(to, luci.util.serialize_data(v2))
                                ))
                            end
                        elseif k == "valueof" then
                            local values, err = self:_read_reference( v2 )
                            if err then
                                return false, scheme:error(so:error(
                                    ERR.REFERENCE(to, luci.util.serialize_data(v2)):child(err)
                                ))
                            end
                            t.type   = "reference"
                            t.values = values
                        elseif k == "required" then
                            t[k] = _bool(v2)
                        else
                            t[k] = t[k] or v2
                        end
                    end
                end

                t.type     = t.type     or "variable"
                t.datatype = t.datatype or "string"
                t.required = t.required or false
            end
        end
    end

    -- Step 3: get all enums
    for i, conf in ipairs( schemes ) do
        for k, v in pairs( conf ) do
            if v['.type'] == "enum" then

                ok, err = _req( TYPE_ENUM, v, { "value", "variable" } )
                if err then return false, scheme:error(err) end

                local r, err = _ref( TYPE_ENUM, v )
                if err then return false, scheme:error(err) end

                local p = self.packages[r[1]]
                if not p then
                    return false, scheme:error(
                        ERR.SME_EBADPACK({scheme:sid(), '', '', v.value}, r[1])
                    )
                end

                local s = p.variables[r[2]]
                if not s then
                    return false, scheme:error(
                        ERR.SME_EBADSECT({scheme:sid(), '', '', v.value}, r[2])
                    )
                end

                local t = s[r[3]]
                if not t then
                    return false, scheme:error(
                        ERR.SME_EBADOPT({scheme:sid(), '', '', v.value}, r[3])
                    )
                end


                local so = scheme:section(r[2])
                local oo = so:option(r[3])
                local eo = oo:enum(v.value)

                if t.type ~= "enum" then
                    return false, scheme:error(ERR.SME_EBADTYPE(eo))
                end

                if not t.values then
                    t.values = { [v.value] = v.title or v.value }
                else
                    t.values[v.value] = v.title or v.value
                end

                if not t.enum_depends then
                    t.enum_depends = { }
                end

                if v.default then
                    if t.default then
                        return false, scheme:error(ERR.SME_EBADDEF(eo))
                    end
                    t.default = v.value
                end

                if v.depends then
                    t.enum_depends[v.value] = self:_read_dependency(
                        v.depends, t.enum_depends[v.value]
                    )

                    if not t.enum_depends[v.value] then
                        return false, scheme:error(so:error(oo:error(
                            ERR.SME_BADDEP(eo, luci.util.serialize_data(v.depends))
                        )))
                    end
                end
            end
        end
    end

    return self
end

-- Read a dependency specification
function UVL._read_dependency( self, values, deps )
    local expr = "%$?[a-zA-Z0-9_]+"
    if values then
        values = ( type(values) == "table" and values or { values } )
        for _, value in ipairs(values) do
            local parts     = luci.util.split( value, "%s*,%s*", nil, true )
            local condition = { }
            for i, val in ipairs(parts) do
                local k, v = unpack(luci.util.split(val, "%s*=%s*", nil, true))

                if k and (
                    k:match("^"..expr.."%."..expr.."%."..expr.."$") or
                    k:match("^"..expr.."%."..expr.."$") or
                    k:match("^"..expr.."$")
                ) then
                    condition[k] = v or true
                else
                    return nil
                end
            end

            if not deps then
                deps = { condition }
            else
                table.insert( deps, condition )
            end
        end
    end

    return deps
end

-- Read a validator specification
function UVL._read_validator( self, values, validators )
    if values then
        values = ( type(values) == "table" and values or { values } )
        for _, value in ipairs(values) do
            local validator

            if value:match("^exec:") then
                validator = value:gsub("^exec:","")
            elseif value:match("^lua:") then
                validator = self:_resolve_function( (value:gsub("^lua:","") ) )
            end

            if validator then
                if not validators then
                    validators = { validator }
                else
                    table.insert( validators, validator )
                end
            else
                return nil
            end
        end

        return validators
    end
end

-- Read a reference specification (XXX: We should validate external configs too...)
function UVL._read_reference( self, values )
    local val = { }
    values = ( type(values) == "table" and values or { values } )

    for _, value in ipairs(values) do
        local ref = luci.util.split(value, ".")

        if #ref == 2 or #ref == 3 then
            local co = luci.uvl.config( self, ref[1] )
            if not co:config() then return false, ERR.UCILOAD(ref[1]) end

            for k, v in pairs(co:config()) do
                if v['.type'] == ref[2] then
                    if #ref == 2 then
                        if v['.anonymous'] == true then
                            return false, ERR.SME_INVREF('', value)
                        end
                        val[k] = k  -- XXX: title/description would be nice
                    elseif v[ref[3]] then
                        val[v[ref[3]]] = v[ref[3]]  -- XXX: dito
                    end
                end
            end
        else
            return false, ERR.SME_BADREF('', value)
        end
    end

    return val, nil
end

-- Resolve given path
function UVL._resolve_function( self, value )
    local path = luci.util.split(value, ".")

    for i=1, #path-1 do
        local stat, mod = luci.util.copcall(
            require, table.concat(path, ".", 1, i)
        )

        if stat and mod then
            for j=i+1, #path-1 do
                if not type(mod) == "table" then
                    break
                end
                mod = mod[path[j]]
                if not mod then
                    break
                end
            end
            mod = type(mod) == "table" and mod[path[#path]] or nil
            if type(mod) == "function" then
                return mod
            end
        end
    end
end


--- Object representation of an uvl item - base class.
uvlitem = luci.util.class()

function uvlitem.cid(self)
    return table.concat( self.cref, '.' )
end

function uvlitem.sid(self)
    return table.concat( self.sref, '.' )
end

function uvlitem.scheme(self, opt)
    local s

    if #self.sref == 4 or #self.sref == 3 then
        s = self.s
            .packages[self.sref[1]]
            .variables[self.sref[2]][self.sref[3]]
    elseif #self.sref == 2 then
        s = self.s
            .packages[self.sref[1]]
            .sections[self.sref[2]]
    else
        s = self.s
            .packages[self.sref[1]]
    end

    if s and opt then
        return s[opt]
    elseif s then
        return s
    end
end

function uvlitem.config(self, opt)
    local c

    if #self.cref == 4 or #self.cref == 3 then
        c = self.c[self.cref[2]][self.cref[3]]
    elseif #self.cref == 2 then
        c = self.c[self.cref[2]]
    else
        c = self.c
    end

    if c and opt then
        return c[opt]
    elseif c then
        return c
    end
end

function uvlitem.title(self)
    return self:scheme() and self:scheme('title') or
        self.cref[3] or self.cref[2] or self.cref[1]
end

function uvlitem.type(self)
    if self.t == luci.uvl.TYPE_CONFIG then
        return 'config'
    elseif self.t == luci.uvl.TYPE_SECTION then
        return 'section'
    elseif self.t == luci.uvl.TYPE_OPTION then
        return 'option'
    elseif self.t == luci.uvl.TYPE_ENUM then
        return 'enum'
    end
end

function uvlitem.error(self, ...)
    if not self.e then
        local errconst = { ERR.CONFIG, ERR.SECTION, ERR.OPTION, ERR.OPTION }
        self.e = errconst[#self.cref]( self )
    end

    return self.e:child( ... )
end

function uvlitem.errors(self)
    return self.e
end

function uvlitem.ok(self)
    return not self:errors()
end

function uvlitem.parent(self)
    if self.p then
        return self.p
    elseif #self.cref == 3 or #self.cref == 4 then
        return luci.uvl.section( self.s, self.c, self.cref[1], self.cref[2] )
    elseif #self.cref == 2 then
        return luci.uvl.config( self.s, self.c, self.cref[1] )
    else
        return nil
    end
end


--- Object representation of a scheme.
-- @class   scheme
-- @cstyle  instance
-- @name    luci.uvl.scheme

--- Scheme instance constructor.
-- @class           function
-- @name            scheme
-- @param scheme    Scheme instance
-- @param co        Configuration data
-- @param c         Configuration name
-- @return          Config instance
scheme = luci.util.class(uvlitem)

function scheme.__init__(self, scheme, co, c)
    if not c then
        c, co = co, nil
    end

    if not co then
        local uci = luci.model.uci.cursor()
        co = uci:get_all(c)
    end

    self.cref = { c }
    self.sref = { c }
    self.c    = co
    self.s    = scheme
    self.t    = luci.uvl.TYPE_SCHEME
end

--- Add an error to scheme.
-- @return  Scheme error context
function scheme.error(self, ...)
    if not self.e then self.e = ERR.SCHEME( self ) end
    return self.e:child( ... )
end

--- Get an associated config object.
-- @return  Config instance
function scheme.config(self)
    local co = luci.uvl.config( self.s, self.cref[1] )
          co.p = self

    return co
end

--- Get all section objects associated with this scheme.
-- @return  Table containing all associated luci.uvl.section instances
function scheme.sections(self)
    local v = { }
    if self.s.packages[self.sref[1]].sections then
        for o, _ in pairs( self.s.packages[self.sref[1]].sections ) do
            table.insert( v, luci.uvl.option(
                self.s, self.c, self.cref[1], self.cref[2], o
            ) )
        end
    end
    return v
end

--- Get an associated section object.
-- @param s Section to select
-- @return  Section instance
function scheme.section(self, s)
    local so = luci.uvl.section( self.s, self.c, self.cref[1], s )
          so.p = self

    return so
end


--- Object representation of a config.
-- @class   config
-- @cstyle  instance
-- @name    luci.uvl.config

--- Config instance constructor.
-- @class           function
-- @name            config
-- @param scheme    Scheme instance
-- @param co        Configuration data
-- @param c         Configuration name
-- @return          Config instance
config = luci.util.class(uvlitem)

function config.__init__(self, scheme, co, c)
    if not c then
        c, co = co, nil
    end

    if not co then
        local uci = luci.model.uci.cursor()
        co = uci:get_all(c)
    end

    self.cref = { c }
    self.sref = { c }
    self.c    = co
    self.s    = scheme
    self.t    = luci.uvl.TYPE_CONFIG
end

--- Get all section objects associated with this config.
-- @return  Table containing all associated luci.uvl.section instances
function config.sections(self)
    local v = { }
    if self.s.packages[self.sref[1]].sections then
        for o, _ in pairs( self.s.packages[self.sref[1]].sections ) do
            table.insert( v, luci.uvl.option(
                self.s, self.c, self.cref[1], self.cref[2], o
            ) )
        end
    end
    return v
end

--- Get an associated section object.
-- @param s Section to select
-- @return  Section instance
function config.section(self, s)
    local so = luci.uvl.section( self.s, self.c, self.cref[1], s )
          so.p = self

    return so
end


--- Object representation of a scheme/config section.
-- @class   module
-- @cstyle  instance
-- @name    luci.uvl.section

--- Section instance constructor.
-- @class           function
-- @name            section
-- @param scheme    Scheme instance
-- @param co        Configuration data
-- @param c         Configuration name
-- @param s         Section name
-- @return          Section instance
section = luci.util.class(uvlitem)

function section.__init__(self, scheme, co, c, s)
    self.cref = { c, s }
    self.sref = { c, co[s] and co[s]['.type'] or s }
    self.c    = co
    self.s    = scheme
    self.t    = luci.uvl.TYPE_SECTION
end

--- Get all option objects associated with this section.
-- @return  Table containing all associated luci.uvl.option instances
function section.variables(self)
    local v = { }
    if self.s.packages[self.sref[1]].variables[self.sref[2]] then
        for o, _ in pairs(
            self.s.packages[self.sref[1]].variables[self.sref[2]]
        ) do
            table.insert( v, luci.uvl.option(
                self.s, self.c, self.cref[1], self.cref[2], o
            ) )
        end
    end
    return v
end

--- Get an associated option object.
-- @param o Option to select
-- @return  Option instance
function section.option(self, o)
    local oo = luci.uvl.option( self.s, self.c, self.cref[1], self.cref[2], o )
          oo.p = self

    return oo
end


--- Object representation of a scheme/config option.
-- @class   module
-- @cstyle  instance
-- @name    luci.uvl.option

--- Section instance constructor.
-- @class           function
-- @name            option
-- @param scheme    Scheme instance
-- @param co        Configuration data
-- @param c         Configuration name
-- @param s         Section name
-- @param o         Option name
-- @return          Option instance
option = luci.util.class(uvlitem)

function option.__init__(self, scheme, co, c, s, o)
    self.cref = { c, s, o }
    self.sref = { c, co[s] and co[s]['.type'] or s, o }
    self.c    = co
    self.s    = scheme
    self.t    = luci.uvl.TYPE_OPTION
end

--- Get the value of this option.
-- @return  The associated configuration value
function option.value(self)
    return self:config()
end

--- Get the associated section information in scheme.
-- @return  Table containing the scheme properties
function option.section(self)
    return self.s.packages[self.sref[1]].sections[self.sref[2]]
end

--- Construct an enum object instance from given or default value.
-- @param v Value to select
-- @return  Enum instance for selected value
function option.enum(self, val)
    return enum(
        self.s, self.c,
        self.cref[1], self.cref[2], self.cref[3],
        val or self:value()
    )
end


--- Object representation of a enum value.
-- @class   module
-- @cstyle  instance
-- @name    luci.uvl.enum

--- Section instance constructor.
-- @class           function
-- @name            enum
-- @param scheme    Scheme instance
-- @param co        Configuration data
-- @param c         Configuration name
-- @param s         Section name
-- @param o         Enum name
-- @param v         Enum value
-- @return          Enum value instance
enum = luci.util.class(option)

function enum.__init__(self, scheme, co, c, s, o, v)
    self.cref = { c, s, o, v }
    self.sref = { c, co[s] and co[s]['.type'] or s, o, v }
    self.c    = co
    self.s    = scheme
    self.t    = luci.uvl.TYPE_ENUM
end