lang: core: Remove the unnecessary func suffix

We don't really need these, it's clear what things are.

lang/core/world/getval.go

@@ -0,0 +1,217 @@
+// Mgmt
+// Copyright (C) 2013-2024+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+// Additional permission under GNU GPL version 3 section 7
+//
+// If you modify this program, or any covered work, by linking or combining it
+// with embedded mcl code and modules (and that the embedded mcl code and
+// modules which link with this program, contain a copy of their source code in
+// the authoritative form) containing parts covered by the terms of any other
+// license, the licensors of this program grant you additional permission to
+// convey the resulting work. Furthermore, the licensors of this program grant
+// the original author, James Shubin, additional permission to update this
+// additional permission if he deems it necessary to achieve the goals of this
+// additional permission.
+
+package coreworld
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/purpleidea/mgmt/lang/funcs"
+	"github.com/purpleidea/mgmt/lang/interfaces"
+	"github.com/purpleidea/mgmt/lang/types"
+	"github.com/purpleidea/mgmt/util/errwrap"
+)
+
+const (
+	// GetValFuncName is the name this function is registered as.
+	GetValFuncName = "getval"
+
+	// arg names...
+	getValArgNameKey = "key"
+
+	// struct field names...
+	getValFieldNameValue  = "value"
+	getValFieldNameExists = "exists"
+)
+
+func init() {
+	funcs.ModuleRegister(ModuleName, GetValFuncName, func() interfaces.Func { return &GetValFunc{} })
+}
+
+// GetValFunc is special function which returns the value of a given key in the
+// exposed world.
+type GetValFunc struct {
+	init *interfaces.Init
+
+	key string
+
+	last   types.Value
+	result types.Value // last calculated output
+
+	watchChan chan error
+}
+
+// String returns a simple name for this function. This is needed so this struct
+// can satisfy the pgraph.Vertex interface.
+func (obj *GetValFunc) String() string {
+	return GetValFuncName
+}
+
+// ArgGen returns the Nth arg name for this function.
+func (obj *GetValFunc) ArgGen(index int) (string, error) {
+	seq := []string{getValArgNameKey}
+	if l := len(seq); index >= l {
+		return "", fmt.Errorf("index %d exceeds arg length of %d", index, l)
+	}
+	return seq[index], nil
+}
+
+// Validate makes sure we've built our struct properly. It is usually unused for
+// normal functions that users can use directly.
+func (obj *GetValFunc) Validate() error {
+	return nil
+}
+
+// Info returns some static info about itself.
+func (obj *GetValFunc) Info() *interfaces.Info {
+	return &interfaces.Info{
+		Pure: false, // definitely false
+		Memo: false,
+		// output is a struct with two fields:
+		// value is the zero value if not exists. A bool for that in other field.
+		Sig: types.NewType(fmt.Sprintf("func(%s str) struct{%s str; %s bool}", getValArgNameKey, getValFieldNameValue, getValFieldNameExists)),
+		Err: obj.Validate(),
+	}
+}
+
+// Init runs some startup code for this function.
+func (obj *GetValFunc) Init(init *interfaces.Init) error {
+	obj.init = init
+	obj.watchChan = make(chan error) // XXX: sender should close this, but did I implement that part yet???
+	return nil
+}
+
+// Stream returns the changing values that this func has over time.
+func (obj *GetValFunc) Stream(ctx context.Context) error {
+	defer close(obj.init.Output) // the sender closes
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel() // important so that we cleanup the watch when exiting
+	for {
+		select {
+		// TODO: should this first chan be run as a priority channel to
+		// avoid some sort of glitch? is that even possible? can our
+		// hostname check with reality (below) fix that?
+		case input, ok := <-obj.init.Input:
+			if !ok {
+				obj.init.Input = nil // don't infinite loop back
+				continue             // no more inputs, but don't return!
+			}
+			//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
+			//	return errwrap.Wrapf(err, "wrong function input")
+			//}
+
+			if obj.last != nil && input.Cmp(obj.last) == nil {
+				continue // value didn't change, skip it
+			}
+			obj.last = input // store for next
+
+			key := input.Struct()[getValArgNameKey].Str()
+			if key == "" {
+				return fmt.Errorf("can't use an empty key")
+			}
+			if obj.init.Debug {
+				obj.init.Logf("key: %s", key)
+			}
+
+			// TODO: support changing the key over time...
+			if obj.key == "" {
+				obj.key = key // store it
+				var err error
+				//  Don't send a value right away, wait for the
+				// first ValueWatch startup event to get one!
+				obj.watchChan, err = obj.init.World.StrWatch(ctx, obj.key) // watch for var changes
+				if err != nil {
+					return err
+				}
+
+			} else if obj.key != key {
+				return fmt.Errorf("can't change key, previously: `%s`", obj.key)
+			}
+
+			continue // we get values on the watch chan, not here!
+
+		case err, ok := <-obj.watchChan:
+			if !ok { // closed
+				// XXX: if we close, perhaps the engine is
+				// switching etcd hosts and we should retry?
+				// maybe instead we should get an "etcd
+				// reconnect" signal, and the lang will restart?
+				return nil
+			}
+			if err != nil {
+				return errwrap.Wrapf(err, "channel watch failed on `%s`", obj.key)
+			}
+
+			result, err := obj.getValue(ctx) // get the value...
+			if err != nil {
+				return err
+			}
+
+			// if the result is still the same, skip sending an update...
+			if obj.result != nil && result.Cmp(obj.result) == nil {
+				continue // result didn't change
+			}
+			obj.result = result // store new result
+
+		case <-ctx.Done():
+			return nil
+		}
+
+		select {
+		case obj.init.Output <- obj.result: // send
+			// pass
+		case <-ctx.Done():
+			return nil
+		}
+	}
+}
+
+// getValue gets the value we're looking for.
+func (obj *GetValFunc) getValue(ctx context.Context) (types.Value, error) {
+	exists := true // assume true
+	val, err := obj.init.World.StrGet(ctx, obj.key)
+	if err != nil && obj.init.World.StrIsNotExist(err) {
+		exists = false // val doesn't exist
+	} else if err != nil {
+		return nil, errwrap.Wrapf(err, "channel read failed on `%s`", obj.key)
+	}
+
+	s := &types.StrValue{V: val}
+	b := &types.BoolValue{V: exists}
+	st := types.NewStruct(obj.Info().Sig.Out)
+	if err := st.Set(getValFieldNameValue, s); err != nil {
+		return nil, errwrap.Wrapf(err, "struct could not add field `%s`, val: `%s`", getValFieldNameValue, s)
+	}
+	if err := st.Set(getValFieldNameExists, b); err != nil {
+		return nil, errwrap.Wrapf(err, "struct could not add field `%s`, val: `%s`", getValFieldNameExists, b)
+	}
+
+	return st, nil // put struct into interface type
+}