1 files changed, 277 insertions, 0 deletions
diff --git a/selector.go b/selector.go
new file mode 100644
index 0000000..5259df2
--- /dev/null
+++ b/selector.go
@@ -0,0 +1,277 @@
+package cnm
+
+import (
+	"errors"
+	"net/url"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// Select selects content from the document based on an extended CNM selector.
+//
+// See ContNet draft/cnm-selector for more information about content selectors.
+//
+// This function may create copies of the document and all container content
+// blocks, but includes non-container blocks untouched in the copy.
+func (doc *Document) Select(selector string) (*Document, error) {
+	deep := true
+	if len(selector) > 0 && selector[0] == '!' {
+		deep = false
+		selector = selector[1:]
+	}
+
+	if len(selector) == 0 {
+		return duplicateBlock(doc, true, deep).(*Document), nil
+	}
+
+	indices, block, err := doc.SelectBlock(selector)
+	if err != nil || block == nil {
+		return nil, err
+	}
+
+	d := NewDocument()
+	if block := selectContent(doc.Content, indices, deep); block != nil {
+		d.Content = block.(*ContentBlock)
+	}
+
+	return d, nil
+}
+
+// SelectIndex selects a content block based on an index path.
+//
+// For example, indices=[]int{1, 4, 2} selects
+// doc.Content.Children()[1].Children()[4].Children(2) if it exists, otherwise
+// returns nil. Note that this is *not* the same as a CNM index selector.
+func (doc *Document) SelectIndex(indices ...int) (block Block) {
+	return SelectIndex(doc.Content, indices...)
+}
+
+// SelectBlock selects section blocks from the document with a selector query.
+//
+// Returns the block index path within content blocks, the target block and, if
+// the query was invalid, an error. All are nil when no block was found with a
+// valid selector.
+//
+// See ContNet draft/cnm-selector for more information.
+func (doc *Document) SelectBlock(selector string) (indices []int, block Block, err error) {
+	if len(selector) == 0 {
+		block = doc
+		indices = []int{}
+		return
+	}
+
+	switch selector[0] {
+	case '/':
+		indices, block, err = doc.selectPath(selector[1:])
+	case '#':
+		indices, block, err = doc.selectTitle(selector[1:])
+	case '$':
+		indices, block, err = doc.selectSectionIndex(selector[1:])
+	default:
+		err = errors.New("cnm-go: invalid selector")
+	}
+
+	return
+}
+
+func (doc *Document) selectPath(selector string) (indices []int, block Block, err error) {
+	ss := []string{}
+	if selector != "" {
+		ss = strings.Split(selector, "/")
+		for i := range ss {
+			ss[i], err = url.PathUnescape(ss[i])
+			if err != nil {
+				return
+			}
+		}
+	}
+	indices, block = selectSearch(doc.Content, ss, false)
+	return
+}
+
+func (doc *Document) selectTitle(selector string) (indices []int, block Block, err error) {
+	if strings.ContainsRune(selector, '/') {
+		err = errors.New("cnm-go: invalid title selector")
+		return
+	}
+	selector, err = url.PathUnescape(selector)
+	if err != nil {
+		return
+	}
+	ss := []string{}
+	if selector != "" {
+		ss = []string{selector}
+	}
+	indices, block = selectSearch(doc.Content, ss, true)
+	return
+}
+
+func (doc *Document) selectSectionIndex(selector string) (indices []int, block Block, err error) {
+	secs := []int{}
+	if selector != "" {
+		for _, s := range strings.Split(selector, ".") {
+			var n uint64
+			n, err = strconv.ParseUint(s, 10, 31)
+			if err != nil {
+				return
+			}
+			secs = append(secs, int(n))
+		}
+	}
+	indices, block = selectSectionIndex(doc.Content, secs)
+	return
+}
+
+func selectSearch(block Block, titles []string, any bool) ([]int, Block) {
+	if len(titles) == 0 {
+		return []int{}, block
+	}
+
+	if bl, ok := block.(*SectionBlock); ok {
+		if len(titles) == 1 && bl.Title() == titles[0] {
+			return []int{}, bl
+		}
+		if any || bl.Title() == titles[0] {
+			if !any {
+				titles = titles[1:]
+			}
+			for i, c := range bl.Children() {
+				if p, b := selectSearch(c, titles, any); b != nil {
+					return append([]int{i}, p...), b
+				}
+			}
+		}
+	} else if bl, ok := block.(ContainerBlock); ok {
+		for i, c := range bl.Children() {
+			if p, b := selectSearch(c, titles, any); b != nil {
+				return append([]int{i}, p...), b
+			}
+		}
+	}
+
+	return nil, nil
+}
+
+func selectSectionIndex(block Block, secs []int) ([]int, Block) {
+	if len(secs) == 0 {
+		return []int{}, block
+	}
+	if bl, ok := block.(ContainerBlock); ok {
+		for i, c := range bl.Children() {
+			if secs[0] < 1 {
+				return nil, nil
+			}
+			if cb, ok2 := c.(*SectionBlock); ok2 {
+				secs[0]-- // starts with 1 for first section
+				if secs[0] == 0 {
+					if len(secs) == 1 {
+						return []int{i}, cb
+					}
+					p, b := selectSectionIndex(cb, secs[1:])
+					if b == nil {
+						return nil, nil
+					}
+					return append([]int{i}, p...), b
+				}
+			} else if _, ok2 := c.(ContainerBlock); ok2 {
+				p, b := selectSectionIndex(c, secs)
+				if b != nil {
+					return append([]int{i}, p...), b
+				}
+			}
+		}
+	}
+	return nil, nil
+}
+
+func selectContent(block Block, indices []int, deep bool) Block {
+	if indices == nil {
+		return nil
+	}
+	if len(indices) == 0 {
+		return duplicateBlock(block, true, deep)
+	}
+	if bl, ok := block.(ContainerBlock); ok {
+		ch := bl.Children()
+		if len(ch) <= indices[0] {
+			return nil
+		}
+		b := duplicateBlock(block, false, true).(ContainerBlock)
+		c := selectContent(ch[indices[0]], indices[1:], deep)
+		if c != nil {
+			b.AppendChild(c)
+		}
+		return b
+	}
+	return nil
+}
+
+func duplicateBlock(block Block, deep, sections bool) Block {
+	if bl, ok := block.(*Document); ok {
+		doc := &Document{
+			Title: bl.Title,
+			Links: bl.Links,
+			Site:  bl.Site,
+		}
+		if deep {
+			doc.Content = duplicateBlock(bl.Content, deep, sections).(*ContentBlock)
+		}
+		return doc
+	}
+	if _, ok := block.(ContainerBlock); !ok {
+		return block
+	}
+
+	var cb ContainerBlock
+
+	switch bl := block.(type) {
+	case *ContentBlock:
+		cb = NewContentBlock(bl.Name(), bl.Args()...)
+	case *HeaderBlock:
+		cb = NewHeaderBlock()
+	case *ListBlock:
+		cb = NewListBlock(bl.Ordered())
+	case *RowBlock:
+		cb = NewRowBlock()
+	case *SectionBlock:
+		cb = NewSectionBlock(bl.Title())
+	case *TableBlock:
+		cb = NewTableBlock()
+	default: // XXX
+		//return nil
+		val := reflect.New(reflect.TypeOf(bl).Elem())
+		cb = val.Interface().(ContainerBlock)
+	}
+
+	if cb != nil && deep {
+		for _, ch := range block.(ContainerBlock).Children() {
+			_, isSection := ch.(*SectionBlock)
+			cb.AppendChild(duplicateBlock(ch, sections || !isSection, sections))
+		}
+	}
+
+	return cb
+}
+
+// SelectIndex selects a child block based on an index path.
+//
+// Note that this is *not* the same as a CNM section index selector.
+func SelectIndex(block Block, indices ...int) Block {
+	if indices == nil {
+		return nil
+	}
+	for len(indices) > 0 {
+		if bl, ok := block.(ContainerBlock); ok {
+			ch := bl.Children()
+			if len(ch) <= indices[0] {
+				return nil
+			}
+			block = ch[indices[0]]
+			indices = indices[1:]
+		} else {
+			return nil
+		}
+	}
+	return block
+}