--- /dev/null
+// Package ast declares the types used to represent syntax trees for HCL
+// (HashiCorp Configuration Language)
+package ast
+
+import (
+ "fmt"
+ "strings"
+
+ "github.com/hashicorp/hcl/hcl/token"
+)
+
+// Node is an element in the abstract syntax tree.
+type Node interface {
+ node()
+ Pos() token.Pos
+}
+
+func (File) node() {}
+func (ObjectList) node() {}
+func (ObjectKey) node() {}
+func (ObjectItem) node() {}
+func (Comment) node() {}
+func (CommentGroup) node() {}
+func (ObjectType) node() {}
+func (LiteralType) node() {}
+func (ListType) node() {}
+
+// File represents a single HCL file
+type File struct {
+ Node Node // usually a *ObjectList
+ Comments []*CommentGroup // list of all comments in the source
+}
+
+func (f *File) Pos() token.Pos {
+ return f.Node.Pos()
+}
+
+// ObjectList represents a list of ObjectItems. An HCL file itself is an
+// ObjectList.
+type ObjectList struct {
+ Items []*ObjectItem
+}
+
+func (o *ObjectList) Add(item *ObjectItem) {
+ o.Items = append(o.Items, item)
+}
+
+// Filter filters out the objects with the given key list as a prefix.
+//
+// The returned list of objects contain ObjectItems where the keys have
+// this prefix already stripped off. This might result in objects with
+// zero-length key lists if they have no children.
+//
+// If no matches are found, an empty ObjectList (non-nil) is returned.
+func (o *ObjectList) Filter(keys ...string) *ObjectList {
+ var result ObjectList
+ for _, item := range o.Items {
+ // If there aren't enough keys, then ignore this
+ if len(item.Keys) < len(keys) {
+ continue
+ }
+
+ match := true
+ for i, key := range item.Keys[:len(keys)] {
+ key := key.Token.Value().(string)
+ if key != keys[i] && !strings.EqualFold(key, keys[i]) {
+ match = false
+ break
+ }
+ }
+ if !match {
+ continue
+ }
+
+ // Strip off the prefix from the children
+ newItem := *item
+ newItem.Keys = newItem.Keys[len(keys):]
+ result.Add(&newItem)
+ }
+
+ return &result
+}
+
+// Children returns further nested objects (key length > 0) within this
+// ObjectList. This should be used with Filter to get at child items.
+func (o *ObjectList) Children() *ObjectList {
+ var result ObjectList
+ for _, item := range o.Items {
+ if len(item.Keys) > 0 {
+ result.Add(item)
+ }
+ }
+
+ return &result
+}
+
+// Elem returns items in the list that are direct element assignments
+// (key length == 0). This should be used with Filter to get at elements.
+func (o *ObjectList) Elem() *ObjectList {
+ var result ObjectList
+ for _, item := range o.Items {
+ if len(item.Keys) == 0 {
+ result.Add(item)
+ }
+ }
+
+ return &result
+}
+
+func (o *ObjectList) Pos() token.Pos {
+ // always returns the uninitiliazed position
+ return o.Items[0].Pos()
+}
+
+// ObjectItem represents a HCL Object Item. An item is represented with a key
+// (or keys). It can be an assignment or an object (both normal and nested)
+type ObjectItem struct {
+ // keys is only one length long if it's of type assignment. If it's a
+ // nested object it can be larger than one. In that case "assign" is
+ // invalid as there is no assignments for a nested object.
+ Keys []*ObjectKey
+
+ // assign contains the position of "=", if any
+ Assign token.Pos
+
+ // val is the item itself. It can be an object,list, number, bool or a
+ // string. If key length is larger than one, val can be only of type
+ // Object.
+ Val Node
+
+ LeadComment *CommentGroup // associated lead comment
+ LineComment *CommentGroup // associated line comment
+}
+
+func (o *ObjectItem) Pos() token.Pos {
+ // I'm not entirely sure what causes this, but removing this causes
+ // a test failure. We should investigate at some point.
+ if len(o.Keys) == 0 {
+ return token.Pos{}
+ }
+
+ return o.Keys[0].Pos()
+}
+
+// ObjectKeys are either an identifier or of type string.
+type ObjectKey struct {
+ Token token.Token
+}
+
+func (o *ObjectKey) Pos() token.Pos {
+ return o.Token.Pos
+}
+
+// LiteralType represents a literal of basic type. Valid types are:
+// token.NUMBER, token.FLOAT, token.BOOL and token.STRING
+type LiteralType struct {
+ Token token.Token
+
+ // comment types, only used when in a list
+ LeadComment *CommentGroup
+ LineComment *CommentGroup
+}
+
+func (l *LiteralType) Pos() token.Pos {
+ return l.Token.Pos
+}
+
+// ListStatement represents a HCL List type
+type ListType struct {
+ Lbrack token.Pos // position of "["
+ Rbrack token.Pos // position of "]"
+ List []Node // the elements in lexical order
+}
+
+func (l *ListType) Pos() token.Pos {
+ return l.Lbrack
+}
+
+func (l *ListType) Add(node Node) {
+ l.List = append(l.List, node)
+}
+
+// ObjectType represents a HCL Object Type
+type ObjectType struct {
+ Lbrace token.Pos // position of "{"
+ Rbrace token.Pos // position of "}"
+ List *ObjectList // the nodes in lexical order
+}
+
+func (o *ObjectType) Pos() token.Pos {
+ return o.Lbrace
+}
+
+// Comment node represents a single //, # style or /*- style commment
+type Comment struct {
+ Start token.Pos // position of / or #
+ Text string
+}
+
+func (c *Comment) Pos() token.Pos {
+ return c.Start
+}
+
+// CommentGroup node represents a sequence of comments with no other tokens and
+// no empty lines between.
+type CommentGroup struct {
+ List []*Comment // len(List) > 0
+}
+
+func (c *CommentGroup) Pos() token.Pos {
+ return c.List[0].Pos()
+}
+
+//-------------------------------------------------------------------
+// GoStringer
+//-------------------------------------------------------------------
+
+func (o *ObjectKey) GoString() string { return fmt.Sprintf("*%#v", *o) }
+func (o *ObjectList) GoString() string { return fmt.Sprintf("*%#v", *o) }
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