From 3ad1c99c416b10ccf2065f1d5f5483d7b3be3600 Mon Sep 17 00:00:00 2001
From: "Gustavo L de Mello (Guz)" <contact@guz.one>
Date: Mon, 13 Jan 2025 22:35:07 -0300
Subject: [PATCH] feat(blogo,plugins,prefixedsourcer): new prefixed sourcer, a
 multisourcer alternative

---
 blogo/plugin_prefixedsourcer.go | 196 ++++++++++++++++++++++++++++++++
 1 file changed, 196 insertions(+)
 create mode 100644 blogo/plugin_prefixedsourcer.go

diff --git a/blogo/plugin_prefixedsourcer.go b/blogo/plugin_prefixedsourcer.go
new file mode 100644
index 0000000..da03581
--- /dev/null
+++ b/blogo/plugin_prefixedsourcer.go
@@ -0,0 +1,196 @@
+// Copyright 2025-present Gustavo "Guz" L. de Mello
+// Copyright 2025-present The Lored.dev Contributors
+//
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package blogo
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"io/fs"
+	"log/slog"
+	"strings"
+)
+
+const prefixedSourcerPluginName = "blogo-prefixedsourcer-sourcer"
+
+type PrefixedSourcer interface {
+	SourcerPlugin
+	Use(Plugin)
+	UseNamed(string, Plugin)
+}
+
+type prefixedSourcer struct {
+	sources map[string]SourcerPlugin
+
+	prefixSeparator  string
+	acceptDuplicated bool
+
+	panicOnInit       bool
+	skipOnHexError    bool
+	skipOnSourceError bool
+	skipOnFSError     bool
+
+	hexFunc HexFunc
+
+	log *slog.Logger
+}
+
+type PrefixedSourcerOpts struct {
+	PrefixSeparator  string
+	AcceptDuplicated bool
+
+	NotPanicOnInit       bool
+	NotSkipOnHexError    bool
+	NotSkipOnSourceError bool
+	NotSkipOnFSError     bool
+
+	HexFunc HexFunc
+
+	Logger *slog.Logger
+}
+
+type HexFunc = func(n int) (string, error)
+
+func hexFunc(n int) (string, error) {
+	bytes := make([]byte, n)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(bytes), nil
+}
+
+func NewPrefixedSourcer(opts ...PrefixedSourcerOpts) PrefixedSourcer {
+	opt := PrefixedSourcerOpts{}
+	if len(opts) > 0 {
+		opt = opts[0]
+	}
+
+	if opt.PrefixSeparator == "" {
+		opt.PrefixSeparator = "/"
+	}
+
+	if opt.HexFunc == nil {
+		opt.HexFunc = hexFunc
+	}
+
+	if opt.Logger == nil {
+		opt.Logger = slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{}))
+	}
+	opt.Logger = opt.Logger.WithGroup(prefixedSourcerPluginName)
+
+	return &prefixedSourcer{
+		sources: map[string]SourcerPlugin{},
+
+		prefixSeparator:  opt.PrefixSeparator,
+		acceptDuplicated: opt.AcceptDuplicated,
+
+		panicOnInit:       !opt.NotPanicOnInit,
+		skipOnSourceError: !opt.NotSkipOnSourceError,
+		skipOnFSError:     !opt.NotSkipOnFSError,
+
+		log: opt.Logger,
+	}
+}
+
+func (p *prefixedSourcer) Name() string {
+	return prefixedSourcerPluginName
+}
+
+func (p *prefixedSourcer) Use(plugin Plugin) {
+	p.UseNamed(plugin.Name(), plugin)
+}
+
+func (p *prefixedSourcer) UseNamed(prefix string, plugin Plugin) {
+	log := p.log.With(slog.String("plugin", plugin.Name()), slog.String("prefix", prefix))
+
+	var sourcer SourcerPlugin
+	if plg, ok := plugin.(SourcerPlugin); ok {
+		sourcer = plg
+	} else {
+		m := fmt.Sprintf("failed to add plugin %q (with prefix %q), since it doesn't implement SourcerPlugin", plugin.Name(), prefix)
+		log.Error(m)
+		if p.panicOnInit {
+			panic(fmt.Sprintf("%s: %s", multiRendererPluginName, m))
+		}
+	}
+
+	if _, ok := p.sources[prefix]; ok && !p.acceptDuplicated {
+		m := fmt.Sprintf(
+			"duplicated prefix (%q) for plugin %q",
+			prefix,
+			plugin.Name(),
+		)
+		log.Error(m)
+		if p.panicOnInit {
+			panic(fmt.Sprintf("%s: %s", multiRendererPluginName, m))
+		}
+		return
+	}
+
+	log.Debug(fmt.Sprintf("Added sourcer plugin, with prefix %q", prefix))
+	p.sources[prefix] = sourcer
+}
+
+func (p *prefixedSourcer) Source() (fs.FS, error) {
+	log := p.log
+
+	fileSystems := make(map[string]fs.FS, len(p.sources))
+
+	for a, s := range p.sources {
+		log = log.With(slog.String("plugin", p.Name()), slog.String("prefix", a))
+		log.Info("Sourcing file system of plugin")
+
+		f, err := s.Source()
+		if err != nil && p.skipOnSourceError {
+			log.Error(
+				"Failed to source file system of plugin, skipping",
+				slog.String("error", err.Error()),
+			)
+		} else if err != nil {
+			log.Error(
+				"Failed to source file system of plugin, returning error",
+				slog.String("error", err.Error()),
+			)
+			return f, err
+		}
+
+		fileSystems[a] = f
+	}
+
+	return &prefixedSourcerFS{
+		fileSystems:     fileSystems,
+		prefixSeparator: p.prefixSeparator,
+	}, nil
+}
+
+type prefixedSourcerFS struct {
+	fileSystems     map[string]fs.FS
+	prefixSeparator string
+}
+
+func (pf *prefixedSourcerFS) Open(name string) (fs.File, error) {
+	prefix, path, found := strings.Cut(name, pf.prefixSeparator)
+	if !found {
+		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
+	}
+
+	if f, ok := pf.fileSystems[prefix]; ok {
+		return f.Open(path)
+	}
+
+	return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
+}