// ingestion/internal/pipeline/links.go
package pipeline

import (
	"fmt"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/mathiasbq/hyperguild/ingestion/internal/wiki"
)

// plainLinkRE matches [[Display Name]] — wikilinks without a slug pipe.
// It does NOT match [[slug|Display]] (those already have a pipe).
var plainLinkRE = regexp.MustCompile(`\[\[([^\]|]+)\]\]`)

// CanonicalizeLinks converts [[Display Name]] wikilinks to [[slug|Display Name]]
// using a title→slug map built from the inventory and current batch.
// Unknown titles are left as-is and returned as warnings.
func CanonicalizeLinks(pages []wiki.Page, inventory map[wiki.PageType][]wiki.Entry) ([]wiki.Page, []string) {
	titleToSlug := buildTitleMap(pages, inventory)

	var allWarnings []string
	out := make([]wiki.Page, len(pages))
	for i, p := range pages {
		newContent, warnings := canonicalizeContent(p.Content, titleToSlug)
		p.Content = newContent
		out[i] = p
		allWarnings = append(allWarnings, warnings...)
	}
	return out, allWarnings
}

// buildTitleMap builds a lowercase-title → slug map from inventory and current batch.
// Current batch entries take precedence over inventory (they may be updates).
func buildTitleMap(pages []wiki.Page, inventory map[wiki.PageType][]wiki.Entry) map[string]string {
	m := make(map[string]string)
	for _, entries := range inventory {
		for _, e := range entries {
			m[strings.ToLower(e.Title)] = e.Slug
		}
	}
	// Current batch overrides inventory
	for _, p := range pages {
		title := extractTitle(p.Content)
		slug := strings.TrimSuffix(filepath.Base(p.Path), ".md")
		if title != "" && slug != "" {
			m[strings.ToLower(title)] = slug
		}
	}
	return m
}

func canonicalizeContent(content string, titleToSlug map[string]string) (string, []string) {
	var warnings []string
	result := plainLinkRE.ReplaceAllStringFunc(content, func(match string) string {
		sub := plainLinkRE.FindStringSubmatch(match)
		if len(sub) < 2 {
			return match
		}
		displayName := sub[1]
		slug, ok := titleToSlug[strings.ToLower(displayName)]
		if !ok {
			warnings = append(warnings, fmt.Sprintf("unknown wikilink: [[%s]]", displayName))
			return match
		}
		return "[[" + slug + "|" + displayName + "]]"
	})
	return result, warnings
}