package vault

import (
	"context"
	"log/slog"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/nextlevelbuilder/goclaw/internal/store"
)

// wikilinkRe matches [[target]] and [[target|display text]].
var wikilinkRe = regexp.MustCompile(`\[\[([^\]|]+)(?:\|[^\]]+)?\]\]`)

// WikilinkMatch is a single parsed wikilink.
type WikilinkMatch struct {
	Target  string // resolved target path (no display text)
	Context string // ~50 chars surrounding the link
	Offset  int    // byte offset in content
}

// ExtractWikilinks parses all [[wikilinks]] from markdown content.
func ExtractWikilinks(content string) []WikilinkMatch {
	matches := wikilinkRe.FindAllStringSubmatchIndex(content, -1)
	var result []WikilinkMatch
	for _, m := range matches {
		if len(m) < 4 {
			continue
		}
		target := strings.TrimSpace(content[m[2]:m[3]])
		if target == "" {
			continue
		}

		// Build context: ~25 bytes before and after the link.
		// Sanitize with ToValidUTF8 so the byte-offset window does not
		// split a multi-byte rune (Vietnamese, CJK, emoji), which would
		// produce invalid UTF-8 that PostgreSQL rejects with
		// "invalid byte sequence for encoding UTF8" (SQLSTATE 22021).
		start := max(m[0]-25, 0)
		end := min(m[1]+25, len(content))
		ctx := strings.ToValidUTF8(content[start:end], "")

		result = append(result, WikilinkMatch{
			Target:  target,
			Context: ctx,
			Offset:  m[0],
		})
	}
	return result
}

// ResolveWikilinkTarget finds a vault_document matching the wikilink target.
// Strategy: exact path -> path+.md -> basename DB query -> nil.
func ResolveWikilinkTarget(ctx context.Context, vs store.VaultStore, target, tenantID, agentID string) (*store.VaultDocument, error) {
	// 1. Exact path match
	doc, err := vs.GetDocument(ctx, tenantID, agentID, target)
	if err == nil && doc != nil {
		return doc, nil
	}

	// 2. With .md suffix
	if !strings.HasSuffix(target, ".md") {
		doc, err = vs.GetDocument(ctx, tenantID, agentID, target+".md")
		if err == nil && doc != nil {
			return doc, nil
		}
	}

	// 3. Basename search via targeted DB query (replaces ListDocuments N+1).
	targetBase := filepath.Base(target)
	doc, err = vs.GetDocumentByBasename(ctx, tenantID, agentID, targetBase)
	if err == nil && doc != nil {
		return doc, nil
	}
	// Try with .md suffix.
	if !strings.HasSuffix(targetBase, ".md") {
		doc, err = vs.GetDocumentByBasename(ctx, tenantID, agentID, targetBase+".md")
		if err == nil && doc != nil {
			return doc, nil
		}
	}

	return nil, nil // unresolved — not an error
}

// SyncDocLinks extracts wikilinks from content, resolves targets,
// and replaces all vault_links for the source document.
func SyncDocLinks(ctx context.Context, vs store.VaultStore, doc *store.VaultDocument, content, tenantID, agentID string) error {
	matches := ExtractWikilinks(content)
	if len(matches) == 0 {
		// No wikilinks — delete existing outbound wikilink-type links only.
		return vs.DeleteDocLinksByType(ctx, tenantID, doc.ID, "wikilink")
	}

	// Delete old outbound wikilink-type links first (replace strategy).
	// Preserves semantic links created by auto-linking.
	if err := vs.DeleteDocLinksByType(ctx, tenantID, doc.ID, "wikilink"); err != nil {
		return err
	}

	// Resolve all wikilinks, then batch-create links in a single call.
	// Deduplicate by (FromDocID, ToDocID, LinkType) to prevent PostgreSQL
	// "ON CONFLICT DO UPDATE command cannot affect row a second time" (SQLSTATE 21000)
	// when the same target appears multiple times in the document.
	type linkKey struct {
		fromDocID string
		toDocID   string
		linkType  string
	}
	seen := make(map[linkKey]int) // key → index in links slice
	var links []store.VaultLink
	for _, m := range matches {
		target, err := ResolveWikilinkTarget(ctx, vs, m.Target, tenantID, agentID)
		if err != nil {
			slog.Debug("vault.link_resolve_error", "target", m.Target, "err", err)
			continue
		}
		if target == nil {
			slog.Debug("vault.link_unresolved", "target", m.Target)
			continue
		}
		k := linkKey{fromDocID: doc.ID, toDocID: target.ID, linkType: "wikilink"}
		if idx, ok := seen[k]; ok {
			links[idx].Context += " | " + m.Context
			continue
		}
		seen[k] = len(links)
		links = append(links, store.VaultLink{
			FromDocID: doc.ID,
			ToDocID:   target.ID,
			LinkType:  "wikilink",
			Context:   m.Context,
		})
	}
	if len(links) == 0 {
		return nil
	}
	return vs.CreateLinks(ctx, links)
}