// DynamoDB JSON parsing and serialization
// Pure functions for converting between DynamoDB JSON format and internal types
package dynamodb

import "core:encoding/json"
import "core:fmt"
import "core:slice"
import "core:strings"

// ============================================================================
// Parsing (JSON → Types)
// ============================================================================

// Parse DynamoDB JSON format into an Item
// Caller owns returned Item
parse_item :: proc(json_bytes: []byte) -> (Item, bool) {
	data, parse_err := json.parse(json_bytes, allocator = context.allocator)
	if parse_err != nil {
		return {}, false
	}
	defer json.destroy_value(data)

	return parse_item_from_value(data)
}

// Parse an Item from an already-parsed JSON Value
// More efficient when you already have a Value (e.g., from request body parsing)
parse_item_from_value :: proc(value: json.Value) -> (Item, bool) {
	obj, ok := value.(json.Object)
	if !ok {
		return {}, false
	}

	item := make(Item)

	for key, val in obj {
		attr_name := strings.clone(key)

		attr_value, attr_ok := parse_attribute_value(val)
		if !attr_ok {
			// Cleanup on error
			for k, v in item {
				delete(k)
				v_copy := v
				attr_value_destroy(&v_copy)
			}
			delete(item)
			delete(attr_name)
			return {}, false
		}

		item[attr_name] = attr_value
	}

	return item, true
}

// Parse a single DynamoDB AttributeValue from JSON
// Format: {"S": "value"}, {"N": "123"}, {"M": {...}}, etc.
parse_attribute_value :: proc(value: json.Value) -> (Attribute_Value, bool) {
	obj, ok := value.(json.Object)
	if !ok {
		return nil, false
	}

	// DynamoDB attribute must have exactly one key (the type indicator)
	if len(obj) != 1 {
		return nil, false
	}

	// Get the single key-value pair
	for type_name, type_value in obj {
		// String
		if type_name == "S" {
			str, str_ok := type_value.(json.String)
			if !str_ok {
				return nil, false
			}
			return String(strings.clone(string(str))), true
		}

		// Number (stored as string)
		if type_name == "N" {
			str, str_ok := type_value.(json.String)
			if !str_ok {
				return nil, false
			}

			// Parse into DDB_Number
			ddb_num, num_ok := parse_ddb_number(string(str))
			if !num_ok {
				return nil, false
			}

			// Clone the string fields since they're slices of the input
			owned_num := clone_ddb_number(ddb_num)
			return owned_num, true
		}

		// Binary (base64 string)
		if type_name == "B" {
			str, str_ok := type_value.(json.String)
			if !str_ok {
				return nil, false
			}
			return Binary(strings.clone(string(str))), true
		}

		// Boolean
		if type_name == "BOOL" {
			b, b_ok := type_value.(json.Boolean)
			if !b_ok {
				return nil, false
			}
			return Bool(b), true
		}

		// Null
		if type_name == "NULL" {
			b, b_ok := type_value.(json.Boolean)
			if !b_ok {
				return nil, false
			}
			return Null(b), true
		}

		// String Set
		if type_name == "SS" {
			arr, arr_ok := type_value.(json.Array)
			if !arr_ok {
				return nil, false
			}

			strings_arr := make([]string, len(arr))

			for item, i in arr {
				str, str_ok := item.(json.String)
				if !str_ok {
					// Cleanup on error
					for j in 0..<i {
						delete(strings_arr[j])
					}
					delete(strings_arr)
					return nil, false
				}
				strings_arr[i] = strings.clone(string(str))
			}

			return String_Set(strings_arr), true
		}

		// Number Set
		if type_name == "NS" {
			arr, arr_ok := type_value.(json.Array)
			if !arr_ok {
				return nil, false
			}

			numbers_arr := make([]DDB_Number, len(arr))

			for item, i in arr {
				str, str_ok := item.(json.String)
				if !str_ok {
					// Cleanup on error
					for j in 0..<i {
						// Clean up DDB_Numbers
						delete(numbers_arr[j].integer_part)
						delete(numbers_arr[j].fractional_part)
					}
					delete(numbers_arr)
					return nil, false
				}

				// Parse into DDB_Number
				ddb_num, num_ok := parse_ddb_number(string(str))
				if !num_ok {
					// Cleanup on error
					for j in 0..<i {
						delete(numbers_arr[j].integer_part)
						delete(numbers_arr[j].fractional_part)
					}
					delete(numbers_arr)
					return nil, false
				}

				// Clone and store
				numbers_arr[i] = clone_ddb_number(ddb_num)
			}

			return DDB_Number_Set(numbers_arr), true
		}

		// Binary Set
		if type_name == "BS" {
			arr, arr_ok := type_value.(json.Array)
			if !arr_ok {
				return nil, false
			}

			binaries_arr := make([]string, len(arr))

			for item, i in arr {
				str, str_ok := item.(json.String)
				if !str_ok {
					// Cleanup on error
					for j in 0..<i {
						delete(binaries_arr[j])
					}
					delete(binaries_arr)
					return nil, false
				}
				binaries_arr[i] = strings.clone(string(str))
			}

			return Binary_Set(binaries_arr), true
		}

		// List
		if type_name == "L" {
			arr, arr_ok := type_value.(json.Array)
			if !arr_ok {
				return nil, false
			}

			list := make([]Attribute_Value, len(arr))

			for item, i in arr {
				val, val_ok := parse_attribute_value(item)
				if !val_ok {
					// Cleanup on error
					for j in 0..<i {
						item_copy := list[j]
						attr_value_destroy(&item_copy)
					}
					delete(list)
					return nil, false
				}
				list[i] = val
			}

			return List(list), true
		}

		// Map
		if type_name == "M" {
			map_obj, map_ok := type_value.(json.Object)
			if !map_ok {
				return nil, false
			}

			attr_map := make(map[string]Attribute_Value)

			for map_key, map_val in map_obj {
				key := strings.clone(map_key)

				val, val_ok := parse_attribute_value(map_val)
				if !val_ok {
					// Cleanup on error
					delete(key)
					for k, v in attr_map {
						delete(k)
						v_copy := v
						attr_value_destroy(&v_copy)
					}
					delete(attr_map)
					return nil, false
				}

				attr_map[key] = val
			}

			return Map(attr_map), true
		}
	}

	return nil, false
}

// ============================================================================
// Serialization (Types → JSON)
// ============================================================================

// Serialize an Item to canonical DynamoDB JSON format
// Keys are sorted alphabetically for deterministic output
serialize_item :: proc(item: Item) -> string {
	builder := strings.builder_make()
	defer strings.builder_destroy(&builder)

	serialize_item_to_builder(&builder, item)

	return strings.clone(strings.to_string(builder))
}

// Serialize an Item to a strings.Builder with deterministic ordering
serialize_item_to_builder :: proc(b: ^strings.Builder, item: Item) {
	// Collect and sort keys for deterministic output
	keys := make([dynamic]string, context.temp_allocator)
	defer delete(keys)

	for key in item {
		append(&keys, key)
	}

	// Sort keys alphabetically
	slice.sort_by(keys[:], proc(a, b: string) -> bool {
		return a < b
	})

	strings.write_string(b, "{")
	for key, i in keys {
		if i > 0 {
			strings.write_string(b, ",")
		}
		fmt.sbprintf(b, `"%s":`, key)
		value := item[key]
		serialize_attribute_value(b, value)
	}
	strings.write_string(b, "}")
}

// Serialize an AttributeValue to DynamoDB JSON format
serialize_attribute_value :: proc(b: ^strings.Builder, attr: Attribute_Value) {
	switch v in attr {
	case String:
		strings.write_string(b, `{"S":"`)
		strings.write_string(b, string(v))
		strings.write_string(b, `"}`)

	case DDB_Number:
		num_str := format_ddb_number(v)
		strings.write_string(b, `{"N":"`)
		strings.write_string(b, num_str)
		strings.write_string(b, `"}`)

	case Binary:
		strings.write_string(b, `{"B":"`)
		strings.write_string(b, string(v))
		strings.write_string(b, `"}`)

	case Bool:
		strings.write_string(b, `{"BOOL":`)
		if bool(v) { strings.write_string(b, "true") } else { strings.write_string(b, "false") }
		strings.write_string(b, "}")

	case Null:
		strings.write_string(b, `{"NULL":true}`)

	case String_Set:
		strings.write_string(b, `{"SS":[`)
		for s, i in v {
			if i > 0 {
				strings.write_string(b, ",")
			}
			fmt.sbprintf(b, `"%s"`, s)
		}
		strings.write_string(b, "]}")

	case DDB_Number_Set:
		strings.write_string(b, `{"NS":[`)
		for num, i in v {
			if i > 0 {
				strings.write_string(b, ",")
			}
			num_str := format_ddb_number(num)
			fmt.sbprintf(b, `"%s"`, num_str)
		}
		strings.write_string(b, "]}")

	case Binary_Set:
		strings.write_string(b, `{"BS":[`)
		for bin, i in v {
			if i > 0 {
				strings.write_string(b, ",")
			}
			fmt.sbprintf(b, `"%s"`, bin)
		}
		strings.write_string(b, "]}")

	case List:
		strings.write_string(b, `{"L":[`)
		for item, i in v {
			if i > 0 {
				strings.write_string(b, ",")
			}
			serialize_attribute_value(b, item)
		}
		strings.write_string(b, "]}")

	case Map:
		strings.write_string(b, `{"M":{`)

		// Collect and sort keys for deterministic output
		keys := make([dynamic]string, context.temp_allocator)
		for key in v {
			append(&keys, key)
		}

		slice.sort_by(keys[:], proc(a, b: string) -> bool {
			return a < b
		})

		for key, i in keys {
			if i > 0 {
				strings.write_string(b, ",")
			}
			fmt.sbprintf(b, `"%s":`, key)
			value := v[key]
			serialize_attribute_value(b, value)
		}

		strings.write_string(b, "}}")
	}
}

// ============================================================================
// Request Parsing Helpers
// ============================================================================

// Extract table name from request body
parse_table_name :: proc(request_body: []byte) -> (string, bool) {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return "", false
	}
	defer json.destroy_value(data)

	root, ok := data.(json.Object)
	if !ok {
		return "", false
	}

	table_name_val, found := root["TableName"]
	if !found {
		return "", false
	}

	table_name_str, str_ok := table_name_val.(json.String)
	if !str_ok {
		return "", false
	}

	return strings.clone(string(table_name_str)), true
}

// Parse Item field from request body
// Returns owned Item
parse_item_from_request :: proc(request_body: []byte) -> (Item, bool) {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return {}, false
	}
	defer json.destroy_value(data)

	root, ok := data.(json.Object)
	if !ok {
		return {}, false
	}

	item_val, found := root["Item"]
	if !found {
		return {}, false
	}

	return parse_item_from_value(item_val)
}

// Parse Key field from request body
// Returns owned Item representing the key
parse_key_from_request :: proc(request_body: []byte) -> (Item, bool) {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return {}, false
	}
	defer json.destroy_value(data)

	root, ok := data.(json.Object)
	if !ok {
		return {}, false
	}

	key_val, found := root["Key"]
	if !found {
		return {}, false
	}

	return parse_item_from_value(key_val)
}

// ============================================================================
// Pagination Helpers
// ============================================================================

// Parse Limit from request body
// Returns 0 if not present
parse_limit :: proc(request_body: []byte) -> int {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return 0
	}
	defer json.destroy_value(data)

	root, ok := data.(json.Object)
	if !ok {
		return 0
	}

	limit_val, found := root["Limit"]
	if !found {
		return 0
	}

	// JSON numbers can be either Integer or Float
	#partial switch v in limit_val {
	case json.Integer:
		return int(v)
	case json.Float:
		return int(v)
	}

	return 0
}

// ============================================================================
// ExclusiveStartKey Parsing (Pagination Input)
//
// Parse ExclusiveStartKey from request body. Requires key_schema so we can
// validate and extract the key, then convert it to a binary storage key.
// Returns the binary key bytes that can be passed straight to scan/query.
// Returns nil (not an error) when the field is absent.
// ============================================================================

parse_exclusive_start_key :: proc(
	request_body: []byte,
	table_name: string,
	key_schema: []Key_Schema_Element,
) -> (result: Maybe([]byte), ok: bool) {
	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
	if parse_err != nil {
		return nil, true // no ESK is fine
	}
	defer json.destroy_value(data)

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

	esk_val, found := root["ExclusiveStartKey"]
	if !found {
		return nil, true // absent → no pagination, that's ok
	}

	// Parse ExclusiveStartKey as a DynamoDB Item
	key_item, item_ok := parse_item_from_value(esk_val)
	if !item_ok {
		return nil, false // present but malformed → real error
	}
	defer item_destroy(&key_item)

	// Validate and extract key struct using schema
	key_struct, key_ok := key_from_item(key_item, key_schema)
	if !key_ok {
		return nil, false // missing required key attributes
	}
	defer key_destroy(&key_struct)

	// Get raw byte values
	key_values, kv_ok := key_get_values(&key_struct)
	if !kv_ok {
		return nil, false
	}

	// Build binary storage key
	binary_key := build_data_key(table_name, key_values.pk, key_values.sk)
	result = binary_key
	ok = true
	return
}

// ============================================================================
// LastEvaluatedKey Generation (Pagination Output)
//
// Decode a binary storage key back into a DynamoDB JSON fragment suitable
// for the "LastEvaluatedKey" field in scan/query responses.
//
// Steps:
//   1. Decode the binary key → table_name, pk_bytes, sk_bytes
//   2. Look up attribute types from metadata (S/N/B)
//   3. Build a Key struct with correctly-typed AttributeValues
//   4. Convert Key → Item → DynamoDB JSON string
// ============================================================================

// Build a Key struct from a binary storage key using metadata for type info.
// This mirrors the Zig buildKeyFromBinaryWithTypes helper.
build_key_from_binary_with_types :: proc(
	binary_key: []byte,
	metadata: ^Table_Metadata,
) -> (key: Key, ok: bool) {
	decoder := Key_Decoder{data = binary_key, pos = 0}

	// Skip entity type byte
	_ = decoder_read_entity_type(&decoder) or_return

	// Skip table name segment
	_ = decoder_read_segment_borrowed(&decoder) or_return

	// Read partition key bytes
	pk_bytes := decoder_read_segment_borrowed(&decoder) or_return

	// Read sort key bytes if present
	sk_bytes: Maybe([]byte) = nil
	if decoder_has_more(&decoder) {
		sk := decoder_read_segment_borrowed(&decoder) or_return
		sk_bytes = sk
	}

	// Get PK attribute type from metadata
	pk_name := table_metadata_get_partition_key_name(metadata).? or_return
	pk_type := table_metadata_get_attribute_type(metadata, pk_name).? or_return

	pk_attr := build_attribute_value_with_type(pk_bytes, pk_type)

	// Build SK attribute if present
	sk_attr: Maybe(Attribute_Value) = nil
	if sk, has_sk := sk_bytes.?; has_sk {
		sk_name := table_metadata_get_sort_key_name(metadata).? or_return
		sk_type := table_metadata_get_attribute_type(metadata, sk_name).? or_return
		sk_attr = build_attribute_value_with_type(sk, sk_type)
	}

	return Key{pk = pk_attr, sk = sk_attr}, true
}

// Serialize a binary storage key as a LastEvaluatedKey JSON fragment.
// Returns a string like: {"pk":{"S":"val"},"sk":{"N":"42"}}
serialize_last_evaluated_key :: proc(
	binary_key: []byte,
	metadata: ^Table_Metadata,
) -> (result: string, ok: bool) {
	key, key_ok := build_key_from_binary_with_types(binary_key, metadata)
	if !key_ok {
		return "", false
	}
	defer key_destroy(&key)

	item := key_to_item(key, metadata.key_schema)
	defer item_destroy(&item)

	return serialize_item(item), true
}