package main

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

type Refs map[string][]string

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

	refs := make(Refs)

	if err != nil {
		return err
	}

	for _, page := range pages {
		links, err := ParseLinks(page.Content)

		if err != nil {
			return err
		}

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

	return refs[p], nil
}