//  Copyright (c) 2026 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 		http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package searcher

import (
	"time"

	"github.com/blevesearch/bleve/v2/numeric"
	"github.com/blevesearch/bleve/v2/search"
	index "github.com/blevesearch/bleve_index_api"
)

// loadDocValuesOnHitWithTypes resolves hit.ID and returns the hit's doc-value
// fields in a new map. It does not touch hit.Fields, so these UDF-input fields
// can't leak into SearchRequest.Fields; the caller owns the map. Returns nil
// when dvReader is nil.
//
// fieldTypes maps a field name to its type: datetime fields decode to an
// RFC3339Nano string, numeric fields to float64. nil treats all prefix-coded
// values as numeric.
func loadDocValuesOnHitWithTypes(hit *search.DocumentMatch, dvReader index.DocValueReader,
	r index.IndexReader, fieldTypes map[string]string) (map[string]interface{}, error) {
	// Always resolve external ID so the callback can read hit.ID.
	if hit.ID == "" && r != nil {
		extID, err := r.ExternalID(hit.IndexInternalID)
		if err != nil {
			return nil, err
		}
		hit.ID = extID
	}

	if dvReader == nil {
		return nil, nil
	}

	fields := make(map[string]interface{})
	err := dvReader.VisitDocValues(hit.IndexInternalID, func(field string, term []byte) {
		value := decodeDocValueTerm(term, fieldTypes[field])
		if value != nil {
			addFieldValueToMap(fields, field, value)
		}
	})
	if err != nil {
		return nil, err
	}

	return fields, nil
}

// addFieldValueToMap adds value under name, mirroring DocumentMatch.AddFieldValue:
// a repeated field name accumulates into a []interface{} slice.
func addFieldValueToMap(fields map[string]interface{}, name string, value interface{}) {
	existingVal, ok := fields[name]
	if !ok {
		fields[name] = value
		return
	}

	valSlice, ok := existingVal.([]interface{})
	if ok {
		valSlice = append(valSlice, value)
	} else {
		valSlice = []interface{}{existingVal, value}
	}
	fields[name] = valSlice
}

// decodeDocValueTerm converts raw doc value bytes into a typed Go value.
// Numeric fields are prefix-coded int64s (only shift-0 terms carry values).
// Boolean fields are stored as "T" or "F".
// Everything else (text/keyword) is returned as a string.
//
// fieldType is the mapping type string for the field (e.g. "datetime",
// "number"). When fieldType is "datetime", the prefix-coded int64 is
// treated as raw nanoseconds (time.UnixNano()) and converted to a UTC
// RFC3339Nano-formatted string. For numeric fields the int64 is decoded via
// Int64ToFloat64 (IEEE 754 bit reinterpretation).
func decodeDocValueTerm(term []byte, fieldType string) interface{} {
	if len(term) == 0 {
		return nil
	}

	// Check if it's a prefix-coded numeric term.
	if valid, shift := numeric.ValidPrefixCodedTermBytes(term); valid {
		// Only shift-0 terms carry the actual value.
		if shift != 0 {
			return nil
		}
		i64, err := numeric.PrefixCoded(term).Int64()
		if err != nil {
			return nil
		}
		if fieldType == "datetime" {
			// Datetime doc values store time.UnixNano() directly as int64.
			// Convert back to a formatted string so callbacks (including
			// JS UDFs) receive a human-readable date like "2022-03-10T00:00:00Z".
			return time.Unix(0, i64).UTC().Format(time.RFC3339Nano)
		}
		// Numeric float64 fields use Float64ToInt64 bit manipulation encoding.
		return numeric.Int64ToFloat64(i64)
	}

	// Boolean fields are stored as "T" or "F".
	if len(term) == 1 {
		if term[0] == 'T' {
			return true
		}
		if term[0] == 'F' {
			return false
		}
	}

	// Default: text/keyword — return as string.
	return string(term)
}