chore: tidy up pkgs (#636)

for readability and towards potentially making helmfile usable as a go library

pkg/tmpl/context_funcs.go

@@ -0,0 +1,208 @@
+package tmpl
+
+import (
+	"fmt"
+	"gopkg.in/yaml.v2"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"text/template"
+)
+
+type Values = map[string]interface{}
+
+func (c *Context) createFuncMap() template.FuncMap {
+	funcMap := template.FuncMap{
+		"exec":           c.Exec,
+		"readFile":       c.ReadFile,
+		"toYaml":         ToYaml,
+		"fromYaml":       FromYaml,
+		"setValueAtPath": SetValueAtPath,
+		"requiredEnv":    RequiredEnv,
+		"get":            get,
+		"getOrNil":       getOrNil,
+		"tpl":            c.Tpl,
+	}
+	if c.preRender {
+		// disable potential side-effect template calls
+		funcMap["exec"] = func(string, []interface{}, ...string) (string, error) {
+			return "", nil
+		}
+		funcMap["readFile"] = func(string) (string, error) {
+			return "", nil
+		}
+	}
+
+	return funcMap
+}
+
+func (c *Context) Exec(command string, args []interface{}, inputs ...string) (string, error) {
+	var input string
+	if len(inputs) > 0 {
+		input = inputs[0]
+	}
+
+	strArgs := make([]string, len(args))
+	for i, a := range args {
+		switch a.(type) {
+		case string:
+			strArgs[i] = a.(string)
+		default:
+			return "", fmt.Errorf("unexpected type of arg \"%s\" in args %v at index %d", reflect.TypeOf(a), args, i)
+		}
+	}
+
+	cmd := exec.Command(command, strArgs...)
+	cmd.Dir = c.basePath
+
+	writeErrs := make(chan error)
+	cmdErrs := make(chan error)
+	cmdOuts := make(chan []byte)
+
+	if len(input) > 0 {
+		stdin, err := cmd.StdinPipe()
+		if err != nil {
+			return "", err
+		}
+		go func(input string, stdin io.WriteCloser) {
+			defer stdin.Close()
+			defer close(writeErrs)
+
+			size := len(input)
+
+			var n int
+			var err error
+			i := 0
+			for {
+				n, err = io.WriteString(stdin, input[i:])
+				if err != nil {
+					writeErrs <- fmt.Errorf("failed while writing %d bytes to stdin of \"%s\": %v", len(input), command, err)
+					break
+				}
+				i += n
+				if n == size {
+					break
+				}
+			}
+		}(input, stdin)
+	}
+
+	go func() {
+		defer close(cmdOuts)
+		defer close(cmdErrs)
+
+		bytes, err := cmd.Output()
+		if err != nil {
+			cmdErrs <- fmt.Errorf("exec cmd=%s args=[%s] failed: %v", command, strings.Join(strArgs, ", "), err)
+		} else {
+			cmdOuts <- bytes
+		}
+	}()
+
+	for {
+		select {
+		case bytes := <-cmdOuts:
+			return string(bytes), nil
+		case err := <-cmdErrs:
+			return "", err
+		case err := <-writeErrs:
+			return "", err
+		}
+	}
+}
+
+func (c *Context) ReadFile(filename string) (string, error) {
+	var path string
+	if filepath.IsAbs(filename) {
+		path = filename
+	} else {
+		path = filepath.Join(c.basePath, filename)
+	}
+
+	bytes, err := c.readFile(path)
+	if err != nil {
+		return "", err
+	}
+	return string(bytes), nil
+}
+
+func (c *Context) Tpl(text string, data interface{}) (string, error) {
+	buf, err := c.RenderTemplateToBuffer(text, data)
+	if err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+
+func ToYaml(v interface{}) (string, error) {
+	data, err := yaml.Marshal(v)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
+func FromYaml(str string) (Values, error) {
+	m := Values{}
+
+	if err := yaml.Unmarshal([]byte(str), &m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+func SetValueAtPath(path string, value interface{}, values Values) (Values, error) {
+	var current interface{}
+	current = values
+	components := strings.Split(path, ".")
+	pathToMap := components[:len(components)-1]
+	key := components[len(components)-1]
+	for _, k := range pathToMap {
+		var elem interface{}
+
+		switch typedCurrent := current.(type) {
+		case map[string]interface{}:
+			v, exists := typedCurrent[k]
+			if !exists {
+				return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" does not exist", path, k)
+			}
+			elem = v
+		case map[interface{}]interface{}:
+			v, exists := typedCurrent[k]
+			if !exists {
+				return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" does not exist", path, k)
+			}
+			elem = v
+		default:
+			return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, k)
+		}
+
+		switch typedElem := elem.(type) {
+		case map[string]interface{}, map[interface{}]interface{}:
+			current = typedElem
+		default:
+			return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, k)
+		}
+	}
+
+	switch typedCurrent := current.(type) {
+	case map[string]interface{}:
+		typedCurrent[key] = value
+	case map[interface{}]interface{}:
+		typedCurrent[key] = value
+	default:
+		return nil, fmt.Errorf("failed to set value at path \"%s\": value for key \"%s\" was not a map", path, key)
+	}
+	return values, nil
+}
+
+func RequiredEnv(name string) (string, error) {
+	if val, exists := os.LookupEnv(name); exists && len(val) > 0 {
+		return val, nil
+	}
+
+	return "", fmt.Errorf("required env var `%s` is not set", name)
+}