// Package index is the (Phase 1) full-text search sync layer for archivdms.
//
// PostgreSQL remains the single source of truth; this package keeps a
// secondary, per-tenant Manticore Search index (Hybrid BM25+Vektor is a later
// phase) in sync with the documents table. Only the write/sync half is
// implemented here — there is deliberately NO search endpoint yet (Phase 2/3).
//
// Design guarantees:
//   - The index is best-effort. When Manticore is not configured (empty DSN)
//     the whole thing degrades to a no-op: the Indexer is nil and every caller
//     skips silently.
//   - An index error must NEVER be propagated to the originating HTTP request.
//     Callers log and move on. Postgres stays authoritative, so a stale index
//     is a recoverable, non-fatal condition (a later reindex CLI, Phase 3,
//     rebuilds it).
//
// This package intentionally has NO dependency on internal/storage to avoid an
// import cycle: storage builds DocumentDoc values and calls into here.
package index

import (
	"context"
	"time"
)

// DocumentDoc is the index representation of a stored document. It is the
// projection of a documents row plus its resolved taxonomy (tags) and ACL
// (visibility group IDs) that the search index needs.
type DocumentDoc struct {
	ID              int64
	TenantID        int64
	Title           string
	DocType         string // deprecated free-text doc_type
	Correspondent   string // deprecated free-text correspondent
	OCRText         string
	Tags            []string
	TagIDs          []int64
	DocTypeID       *int64
	CorrespondentID *int64
	ACLGroupIDs     []int64
	RetainUntil     *time.Time
	CreatedAt       time.Time
	UpdatedAt       time.Time
}

// SearchQuery is the (Phase 3) full-text + attribute query against a single
// tenant's index. It intentionally carries only what the index needs to return
// a ranked list of documents.id values; the caller re-hydrates the full
// document rows from Postgres (the source of truth) afterwards.
type SearchQuery struct {
	// Query is the raw user full-text term. It is escaped before it ever
	// reaches a MATCH() expression — callers pass it verbatim.
	Query string
	// TagIDs, when non-empty, restricts hits to documents carrying ANY of
	// these tag ids (MVA filter).
	TagIDs []int64
	// DocTypeID, when non-nil, restricts hits to that document type.
	DocTypeID *int64
	// ACLGroupIDs applies the group-resolved document ACL: when non-nil, only
	// documents visible to ANY of these permission groups are returned. A nil
	// slice means "no ACL filter" (domain_admin/superadmin). An explicitly
	// empty (non-nil) slice would match nothing — callers must short-circuit
	// that case before querying.
	ACLGroupIDs []int64
	// Page is 1-based; PageSize caps hits per page.
	Page     int
	PageSize int
}

// SearchHit is a single ranked result: a documents.id plus its BM25 score.
type SearchHit struct {
	ID    int64
	Score float64
}

// Indexer syncs a single (tenant-scoped) document index. Implementations must
// never block or fail the calling request on transient backend errors beyond
// returning the error for the caller to log.
type Indexer interface {
	// IndexSync inserts or replaces the document (id-based upsert).
	IndexSync(ctx context.Context, doc DocumentDoc) error
	// Delete removes the document from the index by its documents.id.
	Delete(ctx context.Context, id int64) error
	// Search runs a full-text + attribute query and returns the ranked hits
	// for the requested page plus the total match count (across all pages).
	Search(ctx context.Context, q SearchQuery) (hits []SearchHit, total int, err error)
}

// TenantIndexer hands out per-tenant Indexer instances, each backed by its own
// RT table (documents_tenant_<id>).
type TenantIndexer interface {
	ForTenant(tenantID int64) Indexer
	Close() error
}