lang: Initial implementation of the mgmt language
This is an initial implementation of the mgmt language. It is a declarative (immutable) functional, reactive, domain specific programming language. It is intended to be a language that is: * safe * powerful * easy to reason about With these properties, we hope this language, and the mgmt engine will allow you to model the real-time systems that you'd like to automate. This also includes a number of other associated changes. Sorry for the large size of this patch.
This commit is contained in:
James Shubin
203
lang/funcs/structs/composite.go
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203
lang/funcs/structs/composite.go
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// Mgmt
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// Copyright (C) 2013-2018+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package structs
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import (
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"fmt"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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errwrap "github.com/pkg/errors"
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)
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// CompositeFunc is a function that passes through the value it receives. It is
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// used to take a series of inputs to a list, map or struct, and return that
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// value as a stream that depends on those inputs. It helps the list, map, and
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// struct's that fulfill the Expr interface but expressing a Func method.
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type CompositeFunc struct {
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Type *types.Type // this is the type of the composite value we hold
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Len int // length of list or map (if used)
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init *interfaces.Init
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last types.Value // last value received to use for diff
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result types.Value // last calculated output
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closeChan chan struct{}
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}
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// Validate makes sure we've built our struct properly.
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func (obj *CompositeFunc) Validate() error {
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if obj.Type == nil {
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return fmt.Errorf("must specify a type")
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}
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switch obj.Type.Kind {
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case types.KindList:
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fallthrough
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case types.KindMap:
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fallthrough
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case types.KindStruct:
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return nil
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}
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return fmt.Errorf("can't compose type `%s`", obj.Type.String())
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}
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// Info returns some static info about itself.
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func (obj *CompositeFunc) Info() *interfaces.Info {
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typ := &types.Type{
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Kind: types.KindFunc, // function type
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Map: make(map[string]*types.Type),
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Ord: []string{},
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Out: obj.Type, // this is the output type for the expression
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}
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switch obj.Type.Kind {
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case types.KindList: // wrapped in a struct with `length` many keys
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for i := 0; i < obj.Len; i++ {
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// FIXME: should we .Title the fields or add a prefix?
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key := fmt.Sprintf("%d", i)
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typ.Map[key] = obj.Type.Val // type of each list element
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typ.Ord = append(typ.Ord, key)
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}
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case types.KindMap: // wrapped in a struct with named keys
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for i := 0; i < obj.Len; i++ {
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// each key and val has a value to pass in, and we have
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// a known number of kv pairs, so we pass each in with
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// the index of the kv pair as found in the parse order
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key1 := fmt.Sprintf("key:%d", i)
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typ.Map[key1] = obj.Type.Key // type of each map key
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typ.Ord = append(typ.Ord, key1)
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key2 := fmt.Sprintf("val:%d", i)
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typ.Map[key2] = obj.Type.Val // type of each map val
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typ.Ord = append(typ.Ord, key2)
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}
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case types.KindStruct:
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// map it directly, each key is the right input!
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typ.Map = obj.Type.Map
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typ.Ord = obj.Type.Ord
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}
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return &interfaces.Info{
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Pure: true,
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Memo: false, // TODO: ???
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Sig: typ,
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Err: obj.Validate(),
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}
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}
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// Init runs some startup code for this composite function.
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func (obj *CompositeFunc) Init(init *interfaces.Init) error {
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obj.init = init
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obj.closeChan = make(chan struct{})
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return nil
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}
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// Stream takes an input struct in the format as described in the Func and Graph
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// methods of the Expr, and returns the actual expected value as a stream based
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// on the changing inputs to that value.
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func (obj *CompositeFunc) Stream() error {
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defer close(obj.init.Output) // the sender closes
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for {
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select {
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case input, ok := <-obj.init.Input:
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if !ok {
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return nil // can't output any more
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}
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//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
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// return errwrap.Wrapf(err, "wrong function input")
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//}
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if obj.last != nil && input.Cmp(obj.last) == nil {
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continue // value didn't change, skip it
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}
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obj.last = input // store for next
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var result types.Value
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switch obj.Type.Kind {
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case types.KindList:
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// XXX: this duplicates the same logic that exists in Value() as implemented on *ExprList
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// XXX: have this call that function to get the result?
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result = obj.Type.New() // new list
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input := input.(*types.StructValue) // must be!
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for i := 0; i < obj.Len; i++ { // build it
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value, exists := input.Lookup(fmt.Sprintf("%d", i)) // argNames as integers!
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if !exists {
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return fmt.Errorf("missing input index `%d`", i)
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}
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if err := result.(*types.ListValue).Add(value); err != nil {
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return errwrap.Wrapf(err, "can't build list index `%d`", i)
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}
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}
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case types.KindMap:
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result = obj.Type.New() // new map
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input := (input.(*types.StructValue)).Struct() // must be!
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l := len(input)
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if l%2 != 0 {
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return fmt.Errorf("expected even number of inputs for a map, got: %d", l)
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}
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// each key should be named `key:0`, `val:0`, `key:1`, `val:1`,
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// and so on for as many key pairs as we have... remember that
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// the number of keys pairs is known statically in this case!
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for i := 0; i < l/2; i++ { // build it
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key, exists := input[fmt.Sprintf("key:%d", i)]
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if !exists {
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return fmt.Errorf("missing input key `key:%d`", i)
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}
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val, exists := input[fmt.Sprintf("val:%d", i)]
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if !exists {
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return fmt.Errorf("missing input val `val:%d`", i)
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}
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if err := result.(*types.MapValue).Add(key, val); err != nil {
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return errwrap.Wrapf(err, "can't build map key with index `%d`", i)
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}
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}
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case types.KindStruct:
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result = input
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}
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// skip sending an update...
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if obj.result != nil && result.Cmp(obj.result) == nil {
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continue // result didn't change
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}
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obj.result = result // store new result
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case <-obj.closeChan:
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return nil
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}
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select {
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case obj.init.Output <- obj.result: // send
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// pass
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case <-obj.closeChan:
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return nil
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}
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}
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}
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// Close runs some shutdown code for this function and turns off the stream.
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func (obj *CompositeFunc) Close() error {
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close(obj.closeChan)
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return nil
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}
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