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 && bl.Title() != "" {
		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 && cb.Title() != "" {
				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() {
			sb, isSection := ch.(*SectionBlock)
			cb.AppendChild(duplicateBlock(ch, sections || (!isSection || sb.Title() == ""), 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
}