b134c4b778
This removes the `Close() error` and replaces it with a more modern Stream API that takes a context. This removes boilerplate and makes integration with concurrent code easier. The only downside is that there isn't an explicit cleanup step, but only one function was even using that and it was possible to switch it to a defer in Stream. This also renames the functions from polyfunc to just func which we determine by API not naming.
134 lines
3.8 KiB
Go
134 lines
3.8 KiB
Go
// Mgmt
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// Copyright (C) 2013-2023+ 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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"context"
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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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//"github.com/purpleidea/mgmt/util/errwrap"
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)
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const (
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// VarFuncName is the unique name identifier for this function.
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VarFuncName = "var"
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)
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// VarFunc is a function that passes through a function that came from a bind
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// lookup. It exists so that the reactive function engine type checks correctly.
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type VarFunc struct {
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Type *types.Type // this is the type of the var's value that we hold
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Edge string // name of the edge used
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//Func interfaces.Func // this isn't actually used in the Stream :/
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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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}
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// String returns a simple name for this function. This is needed so this struct
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// can satisfy the pgraph.Vertex interface.
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func (obj *VarFunc) String() string {
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return VarFuncName
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}
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// Validate makes sure we've built our struct properly.
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func (obj *VarFunc) 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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if obj.Edge == "" {
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return fmt.Errorf("must specify an edge name")
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}
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return nil
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}
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// Info returns some static info about itself.
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func (obj *VarFunc) Info() *interfaces.Info {
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var typ *types.Type
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if obj.Type != nil { // don't panic if called speculatively
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typ = &types.Type{
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Kind: types.KindFunc, // function type
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Map: map[string]*types.Type{obj.Edge: obj.Type},
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Ord: []string{obj.Edge},
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Out: obj.Type, // this is the output type for the expression
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}
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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 *VarFunc) Init(init *interfaces.Init) error {
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obj.init = init
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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 *VarFunc) Stream(ctx context.Context) 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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st := input.(*types.StructValue) // must be!
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value, exists := st.Lookup(obj.Edge)
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if !exists {
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return fmt.Errorf("missing expected input argument `%s`", obj.Edge)
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}
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result = value
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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 <-ctx.Done():
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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 <-ctx.Done():
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return nil
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}
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}
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}
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