LogDog: Add collector service implementation.

server/internal/logdog/config/filesystem.go

Index: server/internal/logdog/config/filesystem.go
diff --git a/server/internal/logdog/config/filesystem.go b/server/internal/logdog/config/filesystem.go
new file mode 100644
index 0000000000000000000000000000000000000000..0586f515f7eae11dd93f033240b0bc3f61952342
--- /dev/null
+++ b/server/internal/logdog/config/filesystem.go
@@ -0,0 +1,81 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package config
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"net/url"
+	"os"
+
+	"github.com/luci/luci-go/common/config"
+)
+
+var errNotImplemented = errors.New("not implemented")
+
+// fileConfig is an implementation of config.Interface that represents itself
+// as a configuration instance with one specific ConfigSet containing one
+// specific file.
+//
+// This is a partial implementation of the config.Interface interface sufficient
+// for a ConfigManager to use.
+type fileConfig struct {
+	path string
+
+	configSet  string
+	configPath string
+}
+
+var _ config.Interface = (*fileConfig)(nil)
+
+func (fc *fileConfig) GetConfig(configSet, path string, hashOnly bool) (*config.Config, error) {
+	if configSet != fc.configSet || path != fc.configPath {
+		return nil, config.ErrNoConfig
+	}
+
+	buf := bytes.Buffer{}
+	fd, err := os.Open(fc.path)
+	if err != nil {
+		return nil, err
+	}
+	defer fd.Close()
+
+	_, err = buf.ReadFrom(fd)
+	if err != nil {
+		return nil, err
+	}
+
+	hash := sha256.Sum256(buf.Bytes())
+	return &config.Config{
+		Content:     buf.String(),
+		ContentHash: hex.EncodeToString(hash[:]),
+	}, nil
+}
+
+func (fc *fileConfig) GetConfigByHash(contentHash string) (string, error) {
+	return "", errNotImplemented
+}
+
+func (fc *fileConfig) GetConfigSetLocation(configSet string) (*url.URL, error) {
+	return nil, errNotImplemented
+}
+
+func (fc *fileConfig) GetProjectConfigs(path string, hashesOnly bool) ([]config.Config, error) {
+	return nil, errNotImplemented
+}
+
+func (fc *fileConfig) GetProjects() ([]config.Project, error) {
+	return nil, errNotImplemented
+}
+
+func (fc *fileConfig) GetRefConfigs(path string, hashesOnly bool) ([]config.Config, error) {
+	return nil, errNotImplemented
+}
+
+func (fc *fileConfig) GetRefs(projectID string) ([]string, error) {
+	return nil, errNotImplemented
+}