lang: Unnested the core package from the functions dir

The core package could contain non-functions, so we might as well move
it upwards.

lang/core/deploy/readfile_func.go

@@ -0,0 +1,172 @@
+// 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 <http://www.gnu.org/licenses/>.
+
+package coredeploy
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"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 (
+	// ReadFileFuncName is the name this function is registered as.
+	ReadFileFuncName = "readfile"
+
+	// arg names...
+	readFileArgNameFilename = "filename"
+)
+
+func init() {
+	funcs.ModuleRegister(ModuleName, ReadFileFuncName, func() interfaces.Func { return &ReadFileFunc{} }) // must register the func and name
+}
+
+// ReadFileFunc is a function that reads the full contents from a file in our
+// deploy. The file contents can only change with a new deploy, so this is
+// static. Please note that this is different from the readfile function in the
+// os package.
+type ReadFileFunc struct {
+	init *interfaces.Init
+	data *interfaces.FuncData
+	last types.Value // last value received to use for diff
+
+	filename *string // the active filename
+	result   *string // last calculated output
+}
+
+// String returns a simple name for this function. This is needed so this struct
+// can satisfy the pgraph.Vertex interface.
+func (obj *ReadFileFunc) String() string {
+	return ReadFileFuncName
+}
+
+// SetData is used by the language to pass our function some code-level context.
+func (obj *ReadFileFunc) SetData(data *interfaces.FuncData) {
+	obj.data = data
+}
+
+// ArgGen returns the Nth arg name for this function.
+func (obj *ReadFileFunc) ArgGen(index int) (string, error) {
+	seq := []string{readFileArgNameFilename}
+	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 *ReadFileFunc) Validate() error {
+	return nil
+}
+
+// Info returns some static info about itself.
+func (obj *ReadFileFunc) Info() *interfaces.Info {
+	return &interfaces.Info{
+		Pure: false, // maybe false because the file contents can change
+		Memo: false,
+		Sig:  types.NewType(fmt.Sprintf("func(%s str) str", readFileArgNameFilename)),
+	}
+}
+
+// Init runs some startup code for this function.
+func (obj *ReadFileFunc) Init(init *interfaces.Init) error {
+	obj.init = init
+	if obj.data == nil {
+		// programming error
+		return fmt.Errorf("missing function data")
+	}
+	return nil
+}
+
+// Stream returns the changing values that this func has over time.
+func (obj *ReadFileFunc) Stream(ctx context.Context) error {
+	defer close(obj.init.Output) // the sender closes
+	for {
+		select {
+		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
+
+			filename := input.Struct()[readFileArgNameFilename].Str()
+			// TODO: add validation for absolute path?
+			// TODO: add check for empty string
+			if obj.filename != nil && *obj.filename == filename {
+				continue // nothing changed
+			}
+			obj.filename = &filename
+
+			p := strings.TrimSuffix(obj.data.Base, "/")
+			if p == obj.data.Base { // didn't trim, so we fail
+				// programming error
+				return fmt.Errorf("no trailing slash on Base, got: `%s`", p)
+			}
+			path := p
+
+			if !strings.HasPrefix(*obj.filename, "/") {
+				return fmt.Errorf("filename was not absolute, got: `%s`", *obj.filename)
+				//path += "/" // be forgiving ?
+			}
+			path += *obj.filename
+
+			fs, err := obj.init.World.Fs(obj.data.FsURI) // open the remote file system
+			if err != nil {
+				return errwrap.Wrapf(err, "can't load code from file system `%s`", obj.data.FsURI)
+			}
+			// this is relative to the module dir the func is in!
+			content, err := fs.ReadFile(path) // open the remote file system
+			// We could use it directly, but it feels like less correct.
+			//content, err := obj.data.Fs.ReadFile(path) // open the remote file system
+			if err != nil {
+				return errwrap.Wrapf(err, "can't read file `%s` (%s)", *obj.filename, path)
+			}
+
+			result := string(content) // convert to string
+
+			if obj.result != nil && *obj.result == result {
+				continue // result didn't change
+			}
+			obj.result = &result // store new result
+
+		case <-ctx.Done():
+			return nil
+		}
+
+		select {
+		case obj.init.Output <- &types.StrValue{
+			V: *obj.result,
+		}:
+		case <-ctx.Done():
+			return nil
+		}
+	}
+}