package topdata

import (
	"fmt"
	"os"
	"strings"

	"gopkg.in/yaml.v3"
)

type wikiPagePathDocument struct {
	PagePaths wikiPagePaths `json:"page_paths" yaml:"page_paths"`
}

type wikiPagePaths struct {
	SlugOverrides []wikiPageSlugOverride `json:"slug_overrides" yaml:"slug_overrides"`
}

type wikiPageSlugOverride struct {
	PageID string `json:"page_id" yaml:"page_id"`
	Slug   string `json:"slug" yaml:"slug"`
}

func loadWikiPagePathDeclarations(path string) (map[string]string, error) {
	raw, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return map[string]string{}, nil
	}
	if err != nil {
		return nil, err
	}
	return parseWikiPagePathDeclarations(raw, path)
}

func parseWikiPagePathDeclarations(raw []byte, path string) (map[string]string, error) {
	var doc wikiPagePathDocument
	if err := yaml.Unmarshal(raw, &doc); err != nil {
		return nil, fmt.Errorf("parse wiki page paths %s: %w", path, err)
	}
	overrides := map[string]string{}
	for _, override := range doc.PagePaths.SlugOverrides {
		pageID := strings.TrimSpace(override.PageID)
		slug := strings.TrimSpace(override.Slug)
		if pageID == "" {
			return nil, fmt.Errorf("parse wiki page paths %s: slug override has empty page_id", path)
		}
		if !isCanonicalWikiSlug(slug) {
			return nil, fmt.Errorf("parse wiki page paths %s: page_id %q has invalid slug %q", path, pageID, override.Slug)
		}
		if _, ok := overrides[pageID]; ok {
			return nil, fmt.Errorf("parse wiki page paths %s: duplicate page_id %q", path, pageID)
		}
		overrides[pageID] = slug
	}
	return overrides, nil
}

func isCanonicalWikiSlug(value string) bool {
	if value == "" || value != strings.ToLower(value) {
		return false
	}
	parts := strings.Split(value, "-")
	for _, part := range parts {
		if part == "" {
			return false
		}
		for _, r := range part {
			if !((r >= 'a' && r <= 'z') || (r >= '0' && r <= '9')) {
				return false
			}
		}
	}
	return true
}