package main

import (
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
)

type Reference struct {
	Link ParsedLink
	Name string
}

type Refs map[string][]Reference

func processBackrefs(fp *FilePages) error {
	pages, err := fp.AllPages()

	refs := make(Refs)

	if err != nil {
		return err
	}

	for _, page := range pages {
		content := page.Content

		var listItems []struct {
			Id       int
			Indented int
			Text     string
		}

		err = json.NewDecoder(strings.NewReader(content)).Decode(&listItems)
		if err == nil {
			pageText := ""
			for _, item := range listItems {
				pageText += strings.Repeat("  ", item.Indented) + "* " + item.Text + "\n"
			}

			content = pageText
		}

		links, err := ParseLinks(content)

		if err != nil {
			return err
		}

		for _, link := range links {
			refs[link.PageName] = append(refs[link.PageName], Reference{link, page.Name})
		}
	}

	f, err := os.Create(filepath.Join(fp.dirname, "backrefs.json"))
	if err != nil {
		return err
	}
	defer f.Close()

	err = json.NewEncoder(f).Encode(&refs)

	return err
}

func loadBackrefs(fp *FilePages, p string) (map[string][]Backref, error) {
	refs := make(Refs)
	p = strings.Replace(p, " ", "_", -1)

	f, err := os.Open(filepath.Join(fp.dirname, "backrefs.json"))
	if err != nil {
		return nil, err
	}

	defer f.Close()

	err = json.NewDecoder(f).Decode(&refs)
	if err != nil {
		return nil, err
	}

	result := make(map[string][]Backref)

	for _, ref := range refs[p] {
		title := strings.Replace(ref.Name, "_", " ", -1)
		if _, e := result[ref.Name]; !e {
			result[ref.Name] = nil
		}

		result[ref.Name] = append(result[ref.Name], Backref{
			Name:  ref.Name,
			Title: title,
			Line:  strings.TrimLeft(ref.Link.Line, " *"),
		})
	}

	return result, nil
}