package opensearch

import (
	"context"

	"github.com/Tencent/WeKnora/internal/types"
)

// This file holds the remaining stubs for methods whose real implementation
// has not landed yet — the rolling-reindex swap (swapToVersion) and the
// precise storage estimate. CopyIndices (copy.go), BatchUpdateChunkEnabledStatus
// and BatchUpdateChunkTagID (bulk_update.go) are now implemented. Each
// remaining stub returns ErrFeatureNotEnabled (or, for EstimateStorageSize, a
// conservative lower-bound) so any accidental invocation surfaces loudly.

// EstimateStorageSize: the real implementation that reads cluster
// `_stats` for the per-dim alias arrives in a later change. For now we
// return a conservative lower-bound estimate using the HNSW memory
// formula so the upstream KB-delete guard fails-closed (treats non-empty
// KBs as "may free non-trivial storage, force confirmation") rather than
// failing open.
//
// Formula: N * (1024 content bytes + 4*dimGuess float + 128 HNSW M=16 overhead)
// dimGuess = 768 (common embedding size; the real implementation reads
// the actual dim from the cluster).
func (r *Repository) EstimateStorageSize(
	_ context.Context,
	indexInfoList []*types.IndexInfo,
	_ map[string]any,
) int64 {
	if len(indexInfoList) == 0 {
		return 0
	}
	const (
		contentBytes = 1024 // average chunk content
		embDimGuess  = 768  // common embedding size
		hnswOverhead = 128  // M=16 → 8*M = 128 bytes/vector
	)
	return int64(len(indexInfoList)) * int64(contentBytes+4*embDimGuess+hnswOverhead)
}

// swapToVersion is a stub for the future rolling-reindex swap path.
// Calling it is illegal at this stage — alias is fixed at "_v1" and only
// a follow-up change ships the swap orchestration. The surface exists so
// the future API contract is reviewable now.
//
// Unexported because it is not part of the public
// RetrieveEngineRepository interface — exposing it would require an
// interface widening in internal/types/interfaces.
func (r *Repository) swapToVersion(_ context.Context, _ int, _ int) error {
	return ErrFeatureNotEnabled
}