terraform/config/interpolate.go

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package config
import (
"fmt"
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"regexp"
"strconv"
"strings"
)
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// We really need to replace this with a real parser.
var funcRegexp *regexp.Regexp = regexp.MustCompile(
`(?i)([a-z0-9_]+)\(\s*(?:([.a-z0-9_]+)\s*,\s*)*([.a-z0-9_]+)\s*\)`)
// Interpolation is something that can be contained in a "${}" in a
// configuration value.
//
// Interpolations might be simple variable references, or it might be
// function calls, or even nested function calls.
type Interpolation interface {
Interpolate(map[string]string) (string, error)
Variables() map[string]InterpolatedVariable
}
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// InterpolationFunc is the function signature for implementing
// callable functions in Terraform configurations.
type InterpolationFunc func(map[string]string, ...string) (string, error)
// An InterpolatedVariable is a variable reference within an interpolation.
//
// Implementations of this interface represents various sources where
// variables can come from: user variables, resources, etc.
type InterpolatedVariable interface {
FullKey() string
}
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// FunctionInterpolation is an Interpolation that executes a function
// with some variable number of arguments to generate a value.
type FunctionInterpolation struct {
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Func InterpolationFunc
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Args []Interpolation
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}
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// LiteralInterpolation implements Interpolation for literals. Ex:
// ${"foo"} will equal "foo".
type LiteralInterpolation struct {
Literal string
}
// VariableInterpolation implements Interpolation for simple variable
// interpolation. Ex: "${var.foo}" or "${aws_instance.foo.bar}"
type VariableInterpolation struct {
Variable InterpolatedVariable
}
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// CountVariable is a variable for referencing information about
// the count.
type CountVariable struct {
Type CountValueType
key string
}
// CountValueType is the type of the count variable that is referenced.
type CountValueType byte
const (
CountValueInvalid CountValueType = iota
CountValueIndex
)
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// A ModuleVariable is a variable that is referencing the output
// of a module, such as "${module.foo.bar}"
type ModuleVariable struct {
Name string
Field string
key string
}
// A ResourceVariable is a variable that is referencing the field
// of a resource, such as "${aws_instance.foo.ami}"
type ResourceVariable struct {
Type string // Resource type, i.e. "aws_instance"
Name string // Resource name
Field string // Resource field
Multi bool // True if multi-variable: aws_instance.foo.*.id
Index int // Index for multi-variable: aws_instance.foo.1.id == 1
key string
}
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// A UserVariable is a variable that is referencing a user variable
// that is inputted from outside the configuration. This looks like
// "${var.foo}"
type UserVariable struct {
Name string
Elem string
key string
}
func NewInterpolatedVariable(v string) (InterpolatedVariable, error) {
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if strings.HasPrefix(v, "count.") {
return NewCountVariable(v)
} else if strings.HasPrefix(v, "var.") {
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return NewUserVariable(v)
} else if strings.HasPrefix(v, "module.") {
return NewModuleVariable(v)
} else {
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return NewResourceVariable(v)
}
}
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func (i *FunctionInterpolation) Interpolate(
vs map[string]string) (string, error) {
args := make([]string, len(i.Args))
for idx, a := range i.Args {
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v, err := a.Interpolate(vs)
if err != nil {
return "", err
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}
args[idx] = v
}
return i.Func(vs, args...)
}
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func (i *FunctionInterpolation) GoString() string {
return fmt.Sprintf("*%#v", *i)
}
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func (i *FunctionInterpolation) Variables() map[string]InterpolatedVariable {
result := make(map[string]InterpolatedVariable)
for _, a := range i.Args {
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for k, v := range a.Variables() {
result[k] = v
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}
}
return result
}
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func (i *LiteralInterpolation) Interpolate(
map[string]string) (string, error) {
return i.Literal, nil
}
func (i *LiteralInterpolation) Variables() map[string]InterpolatedVariable {
return nil
}
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func (i *VariableInterpolation) Interpolate(
vs map[string]string) (string, error) {
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v, ok := vs[i.Variable.FullKey()]
if !ok {
return "", fmt.Errorf(
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"%s: value for variable not found",
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i.Variable.FullKey())
}
return v, nil
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}
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func (i *VariableInterpolation) GoString() string {
return fmt.Sprintf("*%#v", *i)
}
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func (i *VariableInterpolation) Variables() map[string]InterpolatedVariable {
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return map[string]InterpolatedVariable{i.Variable.FullKey(): i.Variable}
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}
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func NewCountVariable(key string) (*CountVariable, error) {
var fieldType CountValueType
parts := strings.SplitN(key, ".", 2)
switch parts[1] {
case "index":
fieldType = CountValueIndex
}
return &CountVariable{
Type: fieldType,
key: key,
}, nil
}
func (c *CountVariable) FullKey() string {
return c.key
}
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func NewModuleVariable(key string) (*ModuleVariable, error) {
parts := strings.SplitN(key, ".", 3)
if len(parts) < 3 {
return nil, fmt.Errorf(
"%s: module variables must be three parts: module.name.attr",
key)
}
return &ModuleVariable{
Name: parts[1],
Field: parts[2],
key: key,
}, nil
}
func (v *ModuleVariable) FullKey() string {
return v.key
}
func NewResourceVariable(key string) (*ResourceVariable, error) {
parts := strings.SplitN(key, ".", 3)
if len(parts) < 3 {
return nil, fmt.Errorf(
"%s: resource variables must be three parts: type.name.attr",
key)
}
field := parts[2]
multi := false
var index int
if idx := strings.Index(field, "."); idx != -1 {
indexStr := field[:idx]
multi = indexStr == "*"
index = -1
if !multi {
indexInt, err := strconv.ParseInt(indexStr, 0, 0)
if err == nil {
multi = true
index = int(indexInt)
}
}
if multi {
field = field[idx+1:]
}
}
return &ResourceVariable{
Type: parts[0],
Name: parts[1],
Field: field,
Multi: multi,
Index: index,
key: key,
}, nil
}
func (v *ResourceVariable) ResourceId() string {
return fmt.Sprintf("%s.%s", v.Type, v.Name)
}
func (v *ResourceVariable) FullKey() string {
return v.key
}
func NewUserVariable(key string) (*UserVariable, error) {
name := key[len("var."):]
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elem := ""
if idx := strings.Index(name, "."); idx > -1 {
elem = name[idx+1:]
name = name[:idx]
}
return &UserVariable{
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key: key,
Name: name,
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Elem: elem,
}, nil
}
func (v *UserVariable) FullKey() string {
return v.key
}
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func (v *UserVariable) GoString() string {
return fmt.Sprintf("*%#v", *v)
}