1 files changed, 233 insertions, 0 deletions
diff --git a/internal/templates/templates.go b/internal/templates/templates.go
new file mode 100644
index 0000000..0df384a
--- /dev/null
+++ b/internal/templates/templates.go
@@ -0,0 +1,233 @@
+// Copyright 2018 ThousandEyes Inc.
+//
+// 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 templates
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"text/template"
+
+	"github.com/thousandeyes/shoelaces/internal/log"
+	"github.com/thousandeyes/shoelaces/internal/utils"
+)
+
+const defaultEnvironment = "default"
+
+var varRegex = regexp.MustCompile(`{{\.(.*?)}}`)
+var configNameRegex = regexp.MustCompile(`{{define\s+"(.*?)".*}}`)
+
+// ShoelacesTemplates holds the core attributes for handling the dyanmic configurations
+// in Shoelaces.
+type ShoelacesTemplates struct {
+	envTemplates map[string]shoelacesTemplateEnvironment
+	dataDir      string
+	envDir       string
+	tplExt       string
+}
+
+type shoelacesTemplateEnvironment struct {
+	templateObj  *template.Template
+	templateVars map[string][]string
+}
+
+type shoelacesTemplateInfo struct {
+	name      string
+	variables []string
+}
+
+// New creates and initializes a new ShoelacesTemplates instance a returns a pointer to
+// it.
+func New() *ShoelacesTemplates {
+	e := make(map[string]shoelacesTemplateEnvironment)
+	e[defaultEnvironment] = shoelacesTemplateEnvironment{
+		templateObj:  template.New(""),
+		templateVars: make(map[string][]string),
+	}
+	return &ShoelacesTemplates{envTemplates: e}
+}
+
+func (s *ShoelacesTemplates) parseTemplateInfo(logger log.Logger, path string) shoelacesTemplateInfo {
+	fh, err := os.Open(path)
+	if err != nil {
+		logger.Error("component", "template", "err", err.Error())
+		os.Exit(1)
+	}
+
+	defer fh.Close()
+
+	templateVars := make([]string, 0)
+	scanner := bufio.NewScanner(fh)
+	templateName := ""
+	i := 0
+	for scanner.Scan() {
+		// find variables
+		result := varRegex.FindAllStringSubmatch(scanner.Text(), -1)
+		if varRegex.MatchString(scanner.Text()) {
+			for _, v := range result {
+				// we only want the actual match, being second in the group
+				if !utils.StringInSlice(v[1], templateVars) {
+					templateVars = append(templateVars, v[1])
+				}
+			}
+		}
+		// if first line get name of template
+		if i == 0 {
+			nameResult := configNameRegex.FindAllStringSubmatch(scanner.Text(), -1)
+			templateName = nameResult[0][1]
+		}
+		i++
+	}
+
+	return shoelacesTemplateInfo{name: templateName, variables: templateVars}
+}
+
+func (s *ShoelacesTemplates) checkAddEnvironment(logger log.Logger, environment string) {
+	if _, ok := s.envTemplates[environment]; !ok {
+		c, e := s.envTemplates[defaultEnvironment].templateObj.Clone()
+		if e != nil {
+			logger.Error("component", "template", "msg", "Template for environment already executed", "environment", environment)
+			os.Exit(1)
+		}
+		s.envTemplates[environment] = shoelacesTemplateEnvironment{
+			templateObj:  c,
+			templateVars: make(map[string][]string),
+		}
+	}
+}
+
+func (s *ShoelacesTemplates) addTemplate(logger log.Logger, path string, environment string) error {
+	s.checkAddEnvironment(logger, environment)
+	i := s.parseTemplateInfo(logger, path)
+	_, err := s.envTemplates[environment].templateObj.ParseFiles(path)
+	if err != nil {
+		return err
+	}
+	s.envTemplates[environment].templateVars[i.name] = i.variables
+	return nil
+}
+
+func (s *ShoelacesTemplates) getEnvFromPath(path string) string {
+	envPath := filepath.Join(s.dataDir, s.envDir)
+	if strings.HasPrefix(path, envPath) {
+		return strings.Split(strings.TrimPrefix(path, envPath), "/")[1]
+	}
+	return defaultEnvironment
+}
+
+// ParseTemplates travels the dataDir and loads in an internal structure
+// all the templates found.
+func (s *ShoelacesTemplates) ParseTemplates(logger log.Logger, dataDir string, envDir string, envs []string, tplExt string) {
+	s.dataDir = dataDir
+	s.envDir = envDir
+	s.tplExt = tplExt
+
+	logger.Debug("component", "template", "msg", "Template parsing started", "dir", dataDir)
+
+	tplScannerDefault := func(p string, info os.FileInfo, err error) error {
+		if strings.HasPrefix(p, path.Join(dataDir, envDir)) {
+			return err
+		}
+		if strings.HasSuffix(p, tplExt) {
+			logger.Info("component", "template", "msg", "Parsing file", "file", p)
+			if err := s.addTemplate(logger, p, defaultEnvironment); err != nil {
+				logger.Error("component", "template", "err", err.Error())
+				os.Exit(1)
+			}
+		}
+		return err
+	}
+
+	tplScannerOverride := func(p string, info os.FileInfo, err error) error {
+		if strings.HasSuffix(p, tplExt) {
+			env := s.getEnvFromPath(p)
+			logger.Info("component", "template", "msg", "Parsing ovveride", "environment", env, "file", p)
+
+			if err := s.addTemplate(logger, p, env); err != nil {
+				logger.Error("component", "template", "err", err.Error())
+				os.Exit(1)
+			}
+		}
+		return err
+	}
+
+	if err := filepath.Walk(dataDir, tplScannerDefault); err != nil {
+		panic(err)
+	}
+	logger.Info("component", "template", "msg", "Parsing override files", "dir", path.Join(dataDir, envDir))
+	if err := filepath.Walk(path.Join(dataDir, envDir), tplScannerOverride); err != nil {
+		logger.Info("component", "template", "msg", "No overrides found")
+	}
+	logger.Debug("component", "template", "msg", "Parsing ended")
+}
+
+// RenderTemplate receives a name and a map of parameters, among other
+// arguments, and returns the rendered template. It's aware of the
+// environment, in case of any.
+func (s *ShoelacesTemplates) RenderTemplate(logger log.Logger, configName string, paramMap map[string]interface{}, envName string) (string, error) {
+	if envName == "" {
+		envName = defaultEnvironment
+	}
+	logger.Info("component", "template", "action", "template-request", "template", configName, "env", envName, "parameters", utils.MapToString(paramMap))
+
+	requiredVariables := s.envTemplates[envName].templateVars[configName]
+
+	var b bytes.Buffer
+	err := s.envTemplates[envName].templateObj.ExecuteTemplate(&b, configName, paramMap)
+	// Fall back to default template in case this is non default environment
+	// XXX: this is temporary and will be simplified to reduce the code duplication
+	if err != nil && envName != defaultEnvironment {
+		requiredVariables = s.envTemplates[defaultEnvironment].templateVars[configName]
+		err = s.envTemplates[defaultEnvironment].templateObj.ExecuteTemplate(&b, configName, paramMap)
+	}
+	if err != nil {
+		logger.Info("component", "template", "action", "render-template", "err", err.Error())
+		return "", err
+	}
+	r := b.String()
+	if strings.Contains(r, "<no value>") {
+		missingVariables := ""
+		for _, requiredVariable := range requiredVariables {
+			if !utils.KeyInMap(requiredVariable, paramMap) {
+				if len(missingVariables) > 0 {
+					missingVariables += ", "
+				}
+				missingVariables += requiredVariable
+			}
+		}
+		logger.Info("component", "template", "msg", "Missing variables in request", "variables", missingVariables)
+		return "", errors.New("Missing variables in request: " + missingVariables)
+	}
+
+	return r, nil
+}
+
+// ListVariables receives a template name and return the list of variables
+// that belong to it. It's mainly used by the web frontend to provide a
+// list of dynamic fields to complete before rendering a template.
+func (s *ShoelacesTemplates) ListVariables(templateName, envName string) []string {
+	if e, ok := s.envTemplates[envName]; ok {
+		if v, ok := e.templateVars[templateName]; ok {
+			return v
+		}
+	}
+	var empty []string
+	return empty
+}