package goldmark

import (
	"bytes"
	"fmt"
	// "errors"
	"regexp"

	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/ast"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/text"
	"github.com/yuin/goldmark/util"
)

var contextKeyMeta = parser.NewContextKey()

func isSeparator(line []byte) bool {
	r := regexp.MustCompile(`^\s*-{3,}\s*$`)

	return r.Match(line)
}

type obsidianLinkParser struct{}

var defaultLinkParser = &obsidianLinkParser{}

func (b *obsidianLinkParser) Trigger() []byte {
	// return []byte{'!', '[', ']'}
	fmt.Println("obsidianLinkParser.Trigger()")
	return []byte{'[', ']'}
}

func (b *obsidianLinkParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
	fmt.Println("obsidianLinkParser.Parse()")
	return nil
}

func (b *obsidianLinkParser) Open(parent ast.Node, block text.Reader, pc parser.Context) (ast.Node, parser.State) {
	fmt.Println("obsidianLinkParser.Open()")
	linenum, _ := block.Position()
	if linenum != 0 {
		return nil, parser.NoChildren
	}

	line, _ := block.PeekLine()

	if isSeparator(line) {
		return ast.NewTextBlock(), parser.NoChildren
	}

	return nil, parser.NoChildren
}

func (b *obsidianLinkParser) Continue(node ast.Node, reader text.Reader, pc parser.Context) parser.State {
	line, segment := reader.PeekLine()

	if isSeparator(line) {
		reader.Advance(segment.Len())

		return parser.Close
	}

	node.Lines().Append(segment)

	return parser.Continue | parser.NoChildren
}

func (b *obsidianLinkParser) Close(node ast.Node, reader text.Reader, pc parser.Context) {
	lines := node.Lines()

	var buf bytes.Buffer

	for i := 0; i < lines.Len(); i++ {
		segment := lines.At(i)
		buf.Write(segment.Value(reader.Source()))
	}
	pc.Set(contextKeyMeta, buf)
	node.Parent().RemoveChild(node.Parent(), node)
}

func (b *obsidianLinkParser) CanInterruptParagraph() bool {
	return false
}

func (b *obsidianLinkParser) CanAcceptIndentedLine() bool {
	return false
}

type obsidianLinkExtension struct{}

func (ole *obsidianLinkExtension) Extend(m goldmark.Markdown) {
	m.Parser().AddOptions(
		parser.WithInlineParsers(
			util.Prioritized(defaultLinkParser, 0),
		),
	)
}

var ObsidianLinkExtension = &obsidianLinkExtension{}