// gsi_handlers.odin — GSI-related HTTP handler helpers
//
// This file lives in the main package alongside main.odin.
// It provides:
//   1. parse_global_secondary_indexes — parse GSI definitions from CreateTable request
//   2. parse_index_name              — extract IndexName from Query/Scan requests
//   3. Projection type helper for response building
package main

import "core:encoding/json"
import "core:strings"
import "dynamodb"

// ============================================================================
// Parse GlobalSecondaryIndexes from CreateTable request body
//
// DynamoDB CreateTable request format for GSIs:
// {
//   "GlobalSecondaryIndexes": [
//     {
//       "IndexName": "email-index",
//       "KeySchema": [
//         { "AttributeName": "email", "KeyType": "HASH" },
//         { "AttributeName": "timestamp", "KeyType": "RANGE" }
//       ],
//       "Projection": {
//         "ProjectionType": "ALL" | "KEYS_ONLY" | "INCLUDE",
//         "NonKeyAttributes": ["attr1", "attr2"]  // only for INCLUDE
//       }
//     }
//   ]
// }
//
// Returns nil if no GSI definitions are present (valid — GSIs are optional).
// ============================================================================

parse_global_secondary_indexes :: proc(
	root: json.Object,
	attr_defs: []dynamodb.Attribute_Definition,
) -> Maybe([]dynamodb.Global_Secondary_Index) {
	gsi_val, found := root["GlobalSecondaryIndexes"]
	if !found {
		return nil
	}

	gsi_arr, ok := gsi_val.(json.Array)
	if !ok || len(gsi_arr) == 0 {
		return nil
	}

	gsis := make([]dynamodb.Global_Secondary_Index, len(gsi_arr))

	for elem, i in gsi_arr {
		elem_obj, elem_ok := elem.(json.Object)
		if !elem_ok {
			cleanup_parsed_gsis(gsis[:i])
			delete(gsis)
			return nil
		}

		gsi, gsi_ok := parse_single_gsi(elem_obj, attr_defs)
		if !gsi_ok {
			cleanup_parsed_gsis(gsis[:i])
			delete(gsis)
			return nil
		}

		gsis[i] = gsi
	}

	return gsis
}

@(private = "file")
parse_single_gsi :: proc(
	obj: json.Object,
	attr_defs: []dynamodb.Attribute_Definition,
) -> (dynamodb.Global_Secondary_Index, bool) {
	gsi: dynamodb.Global_Secondary_Index

	// IndexName (required)
	idx_val, idx_found := obj["IndexName"]
	if !idx_found {
		return {}, false
	}
	idx_str, idx_ok := idx_val.(json.String)
	if !idx_ok {
		return {}, false
	}
	gsi.index_name = strings.clone(string(idx_str))

	// KeySchema (required)
	ks_val, ks_found := obj["KeySchema"]
	if !ks_found {
		delete(gsi.index_name)
		return {}, false
	}
	ks_arr, ks_ok := ks_val.(json.Array)
	if !ks_ok || len(ks_arr) == 0 || len(ks_arr) > 2 {
		delete(gsi.index_name)
		return {}, false
	}

	key_schema := make([]dynamodb.Key_Schema_Element, len(ks_arr))
	hash_count := 0

	for ks_elem, j in ks_arr {
		ks_obj, kobj_ok := ks_elem.(json.Object)
		if !kobj_ok {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}

		an_val, an_found := ks_obj["AttributeName"]
		if !an_found {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}
		an_str, an_ok := an_val.(json.String)
		if !an_ok {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}

		kt_val, kt_found := ks_obj["KeyType"]
		if !kt_found {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}
		kt_str, kt_ok := kt_val.(json.String)
		if !kt_ok {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}

		kt, kt_parse_ok := dynamodb.key_type_from_string(string(kt_str))
		if !kt_parse_ok {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}

		if kt == .HASH {
			hash_count += 1
		}

		// Validate that the GSI key attribute is in AttributeDefinitions
		attr_defined := false
		for ad in attr_defs {
			if ad.attribute_name == string(an_str) {
				attr_defined = true
				break
			}
		}
		if !attr_defined {
			for k in 0..<j { delete(key_schema[k].attribute_name) }
			delete(key_schema)
			delete(gsi.index_name)
			return {}, false
		}

		key_schema[j] = dynamodb.Key_Schema_Element{
			attribute_name = strings.clone(string(an_str)),
			key_type = kt,
		}
	}

	// Must have exactly one HASH key
	if hash_count != 1 {
		for ks in key_schema { delete(ks.attribute_name) }
		delete(key_schema)
		delete(gsi.index_name)
		return {}, false
	}

	gsi.key_schema = key_schema

	// Projection (optional — defaults to ALL)
	gsi.projection.projection_type = .ALL
	if proj_val, proj_found := obj["Projection"]; proj_found {
		if proj_obj, proj_ok := proj_val.(json.Object); proj_ok {
			if pt_val, pt_found := proj_obj["ProjectionType"]; pt_found {
				if pt_str, pt_ok := pt_val.(json.String); pt_ok {
					switch string(pt_str) {
					case "ALL":       gsi.projection.projection_type = .ALL
					case "KEYS_ONLY": gsi.projection.projection_type = .KEYS_ONLY
					case "INCLUDE":   gsi.projection.projection_type = .INCLUDE
					}
				}
			}

			// NonKeyAttributes (only valid for INCLUDE projection)
			if nka_val, nka_found := proj_obj["NonKeyAttributes"]; nka_found {
				if nka_arr, nka_ok := nka_val.(json.Array); nka_ok && len(nka_arr) > 0 {
					nka := make([]string, len(nka_arr))
					for attr_val, k in nka_arr {
						if attr_str, attr_ok := attr_val.(json.String); attr_ok {
							nka[k] = strings.clone(string(attr_str))
						}
					}
					gsi.projection.non_key_attributes = nka
				}
			}
		}
	}

	return gsi, true
}

@(private = "file")
cleanup_parsed_gsis :: proc(gsis: []dynamodb.Global_Secondary_Index) {
	for gsi in gsis {
		delete(gsi.index_name)
		for ks in gsi.key_schema {
			delete(ks.attribute_name)
		}
		delete(gsi.key_schema)
		if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka {
			for attr in nka { delete(attr) }
			delete(nka)
		}
	}
}

// ============================================================================
// Parse IndexName from Query/Scan request
// ============================================================================

parse_index_name :: proc(request_body: []byte) -> Maybe(string) {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return nil
	}
	defer json.destroy_value(data)

	root, root_ok := data.(json.Object)
	if !root_ok {
		return nil
	}

	idx_val, found := root["IndexName"]
	if !found {
		return nil
	}

	idx_str, ok := idx_val.(json.String)
	if !ok {
		return nil
	}

	return string(idx_str)
}

// ============================================================================
// Projection type to string for DescribeTable response
// ============================================================================

projection_type_to_string :: proc(pt: dynamodb.Projection_Type) -> string {
	switch pt {
	case .ALL:       return "ALL"
	case .KEYS_ONLY: return "KEYS_ONLY"
	case .INCLUDE:   return "INCLUDE"
	}
	return "ALL"
}