// Notes implements a data structure for reasoning about and rendering
// markdown notes
package notes

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"html/template"
	"log"
	"os"
	"path/filepath"

	"forgejo.gwairfelin.com/max/gonotes/internal/conf"
	markdown "github.com/teekennedy/goldmark-markdown"
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/ast"
	"github.com/yuin/goldmark/extension"
	astext "github.com/yuin/goldmark/extension/ast"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/text"
	"github.com/yuin/goldmark/util"
)

// Note is the central data structure.  It can be Saved, Rendered and Loaded
// using the Save, Render and LoadNote functions.
type Note struct {
	Title        string
	BodyRendered template.HTML
	Body         []byte
}

func fmtPath(path string) string {
	return fmt.Sprintf("%s.%s", path, conf.Conf.Extension)
}

// Save a note to a path derived from the title
func (n *Note) Save() error {
	filename := filepath.Join(conf.Conf.NotesDir, fmtPath(n.EncodedTitle()))
	return os.WriteFile(filename, n.Body, 0600)
}

// Render the markdown content of the note to HTML
func (n *Note) Render() {
	var buf bytes.Buffer
	md := goldmark.New(
		goldmark.WithExtensions(
			extension.TaskList,
		),
	)
	err := md.Convert(n.Body, &buf)
	if err != nil {
		log.Fatal(err)
	}

	n.BodyRendered = template.HTML(buf.String())
}

// LoadNote from the disk. The path is derived from the title
func LoadNote(encodedTitle string) (*Note, error) {
	filename := filepath.Join(conf.Conf.NotesDir, fmtPath(encodedTitle))
	body, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	title := DecodeTitle(encodedTitle)
	return &Note{Title: title, Body: body}, nil
}

func DeleteNote(title string) error {
	filename := filepath.Join(conf.Conf.NotesDir, fmtPath(title))
	return os.Remove(filename)
}

func (n *Note) EncodedTitle() string {
	return base64.StdEncoding.EncodeToString([]byte(n.Title))
}

type toggleCheckboxTransformer struct{ nthBox int }

func (t *toggleCheckboxTransformer) Transform(node *ast.Document, reader text.Reader, pc parser.Context) {
	boxesFound := 0

	// Walk to find checkbox, toggle checked status
	ast.Walk(node, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
		if !entering {
			return ast.WalkContinue, nil
		}

		box, ok := n.(*astext.TaskCheckBox)
		if !ok {
			return ast.WalkContinue, nil
		}

		if boxesFound < t.nthBox {
			boxesFound += 1
			return ast.WalkContinue, nil
		}

		box.IsChecked = !box.IsChecked
		return ast.WalkStop, nil
	})
}

func (r *markdown.Renderer) renderTaskCheckBox(node ast.Node, entering bool) ast.WalkStatus {
	if entering {
		var itemPrefix []byte
		l := r.rc.lists[len(r.rc.lists)-1]

		if l.list.IsOrdered() {
			itemPrefix = append(itemPrefix, []byte(fmt.Sprint(l.num))...)
			r.rc.lists[len(r.rc.lists)-1].num += 1
		}
		itemPrefix = append(itemPrefix, l.list.Marker, ' ')
		// Prefix the current line with the item prefix
		r.rc.writer.PushPrefix(itemPrefix, 0, 0)
		// Prefix subsequent lines with padding the same length as the item prefix
		indentLen := int(max(r.config.NestedListLength, NestedListLengthMinimum))
		indent := bytes.Repeat([]byte{' '}, indentLen)
		r.rc.writer.PushPrefix(bytes.Repeat(indent, len(itemPrefix)), 1)
	} else {
		r.rc.writer.PopPrefix()
		r.rc.writer.PopPrefix()
	}
	return ast.WalkContinue
}

func (n *Note) ToggleBox(nthBox int) {
	log.Printf("Toggling %dth box", nthBox)

	checkboxTransformer := toggleCheckboxTransformer{nthBox: nthBox}
	transformer := util.Prioritized(&checkboxTransformer, 0)

	renderer := markdown.NewRenderer()
	renderer.Register(astext.KindTaskCheckBox, func(writer util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
	})

	var buf bytes.Buffer
	md := goldmark.New(
		goldmark.WithExtensions(
			extension.TaskList,
		),
		goldmark.WithRenderer(markdown.NewRenderer()),
		goldmark.WithParserOptions(parser.WithASTTransformers(transformer)),
	)

	md.Convert(n.Body, &buf)
	n.Body = buf.Bytes()
	n.Save()
}

func DecodeTitle(encodedTitle string) string {
	title, err := base64.StdEncoding.DecodeString(encodedTitle)
	if err != nil {
		log.Printf("Couldn't decode base64 string '%s': %s", encodedTitle, err)
	}

	return string(title)
}