package v2

import (
	"bytes"
	"database/sql"
	"errors"
	"fmt"
	"strconv"
	"strings"
)

type conversionFunc func(value sql.RawBytes) (interface{}, error)

// ParseInt parses the given sql.RawBytes value into an int64.
// It returns the parsed value and an error if the parsing fails.
func ParseInt(value sql.RawBytes) (interface{}, error) {
	v, err := strconv.ParseInt(string(value), 10, 64)

	// Ignore ErrRange.  When this error is set the returned value is "the
	// maximum magnitude integer of the appropriate bitSize and sign."
	var numErr *strconv.NumError
	if errors.As(err, &numErr) && errors.Is(numErr, strconv.ErrRange) {
		return v, nil
	}

	return v, err
}

// ParseUint parses the given sql.RawBytes value into an uint64.
// It returns the parsed value and an error if the parsing fails.
func ParseUint(value sql.RawBytes) (interface{}, error) {
	return strconv.ParseUint(string(value), 10, 64)
}

// ParseFloat parses the given sql.RawBytes value into a float64.
// It returns the parsed value and an error if the parsing fails.
func ParseFloat(value sql.RawBytes) (interface{}, error) {
	return strconv.ParseFloat(string(value), 64)
}

// ParseBoolAsInteger parses the given sql.RawBytes value into an int64
// representing a boolean value. It returns 1 for "YES" or "ON" and 0 otherwise.
func ParseBoolAsInteger(value sql.RawBytes) (interface{}, error) {
	if bytes.EqualFold(value, []byte("YES")) || bytes.EqualFold(value, []byte("ON")) {
		return int64(1), nil
	}

	return int64(0), nil
}

// ParseString parses the given sql.RawBytes value into a string.
// It returns the parsed value and an error if the parsing fails.
func ParseString(value sql.RawBytes) (interface{}, error) {
	return string(value), nil
}

// parseWsrepLatency parses the given sql.RawBytes value into a map
// containing 5 distinct float64 values. These represent min/avg/max/stdev/sample_size.
// It returns an error if the value is unrecognized.
func parseWsrepLatency(value sql.RawBytes) (interface{}, error) {
	keys := []string{"min", "avg", "max", "stdev", "sample_size"}
	parts := strings.Split(string(value), "/")
	if len(parts) != len(keys) {
		return nil, fmt.Errorf("unsupported amount of values in wsrep_evs_repl_latency, got %d expected %d", len(parts), len(keys))
	}

	result := make(map[string]interface{}, len(keys))

	for i, key := range keys {
		val, err := strconv.ParseFloat(parts[i], 64)
		if err != nil {
			return nil, fmt.Errorf("failed to parse %s value: %w", key, err)
		}
		result[key] = val
	}

	return result, nil
}

// ParseWsrepProviderOptions parses the given sql.RawBytes value into a map
// containing all wsrep Provider options settings.
func parseWsrepProviderOptions(value sql.RawBytes) (interface{}, error) {
	parts := strings.Split(strings.TrimSpace(string(value)), ";")
	result := make(map[string]interface{})
	for _, setting := range parts {
		key, data, found := strings.Cut(setting, "=")

		// empty string at the end of the field, skip
		if len(setting) != 0 && !found {
			return nil, fmt.Errorf("invalid key-value pair for %q", setting)
		}

		key = strings.TrimSpace(key)
		data = strings.TrimSpace(data)
		if len(data) == 0 {
			continue // empty value, no point in continuing
		}

		// Only process gcache.size for now
		if key != "gcache.size" {
			continue
		}
		key = strings.Replace(key, ".", "_", -1)

		// Extract the size suffix for values like 128M
		suffix := data[len(data)-1:]
		value := data[:len(data)-1]

		// Determine the scaling factor from the suffix
		var factor uint64
		switch strings.ToUpper(suffix) {
		case "K":
			factor = 1024
		case "M":
			factor = 1024 * 1024
		case "G":
			factor = 1024 * 1024 * 1024
		case "T":
			factor = 1024 * 1024 * 1024 * 1024
		case "P":
			factor = 1024 * 1024 * 1024 * 1024 * 1024
		case "E":
			factor = 1024 * 1024 * 1024 * 1024 * 1024 * 1024
		default:
			// We got no known unit so parse the whole data as value
			value = data
			factor = 1
		}

		// Compute the actual value
		v, err := strconv.ParseUint(value, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("failed to parse value %q: %w", data, err)
		}
		result[key] = v * factor
	}
	return result, nil
}

// ParseGTIDMode parses the given sql.RawBytes value into an int64
// representing the GTID mode. It returns an error if the value is unrecognized.
func ParseGTIDMode(value sql.RawBytes) (interface{}, error) {
	// https://dev.mysql.com/doc/refman/8.0/en/replication-mode-change-online-concepts.html
	v := string(value)
	switch v {
	case "OFF":
		return int64(0), nil
	case "ON":
		return int64(1), nil
	case "OFF_PERMISSIVE":
		return int64(0), nil
	case "ON_PERMISSIVE":
		return int64(1), nil
	default:
		return nil, fmt.Errorf("unrecognized gtid_mode: %q", v)
	}
}

// ParseValue attempts to parse the given sql.RawBytes value into an appropriate type.
// It returns the parsed value and an error if the parsing fails.
func ParseValue(value sql.RawBytes) (interface{}, error) {
	if bytes.EqualFold(value, []byte("YES")) || bytes.Equal(value, []byte("ON")) {
		return int64(1), nil
	}

	if bytes.EqualFold(value, []byte("NO")) || bytes.Equal(value, []byte("OFF")) {
		return int64(0), nil
	}

	if val, err := strconv.ParseInt(string(value), 10, 64); err == nil {
		return val, nil
	}
	if val, err := strconv.ParseUint(string(value), 10, 64); err == nil {
		return val, nil
	}
	if val, err := strconv.ParseFloat(string(value), 64); err == nil {
		return val, nil
	}

	if len(string(value)) > 0 {
		return string(value), nil
	}

	return nil, fmt.Errorf("unconvertible value: %q", string(value))
}

var globalStatusConversions = map[string]conversionFunc{
	"innodb_available_undo_logs":    ParseUint,
	"innodb_buffer_pool_pages_misc": ParseUint,
	"innodb_data_pending_fsyncs":    ParseUint,
	"ssl_ctx_verify_depth":          ParseUint,
	"ssl_verify_depth":              ParseUint,

	// see https://galeracluster.com/library/documentation/galera-status-variables.html
	"wsrep_apply_oooe":           ParseFloat,
	"wsrep_apply_oool":           ParseFloat,
	"wsrep_apply_window":         ParseFloat,
	"wsrep_cert_deps_distance":   ParseFloat,
	"wsrep_cert_interval":        ParseFloat,
	"wsrep_commit_oooe":          ParseFloat,
	"wsrep_commit_oool":          ParseFloat,
	"wsrep_commit_window":        ParseFloat,
	"wsrep_evs_repl_latency":     parseWsrepLatency,
	"wsrep_flow_control_paused":  ParseFloat,
	"wsrep_local_index":          ParseUint,
	"wsrep_local_recv_queue_avg": ParseFloat,
	"wsrep_local_send_queue_avg": ParseFloat,
}

var globalVariableConversions = map[string]conversionFunc{
	// see https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html
	// see https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html
	"delay_key_write":                ParseString,        // ON, OFF, ALL
	"enforce_gtid_consistency":       ParseString,        // ON, OFF, WARN
	"event_scheduler":                ParseString,        // YES, NO, DISABLED
	"have_openssl":                   ParseBoolAsInteger, // alias for have_ssl
	"have_ssl":                       ParseBoolAsInteger, // YES, DISABLED
	"have_symlink":                   ParseBoolAsInteger, // YES, NO, DISABLED
	"session_track_gtids":            ParseString,
	"session_track_transaction_info": ParseString,
	"ssl_fips_mode":                  ParseString,
	"use_secondary_engine":           ParseString,

	// https://dev.mysql.com/doc/refman/5.7/en/replication-options-binary-log.html
	// https://dev.mysql.com/doc/refman/8.0/en/replication-options-binary-log.html
	"transaction_write_set_extraction": ParseString,

	// https://dev.mysql.com/doc/refman/5.7/en/replication-options-replica.html
	// https://dev.mysql.com/doc/refman/8.0/en/replication-options-replica.html
	"slave_skip_errors": ParseString,

	// https://dev.mysql.com/doc/refman/5.7/en/replication-options-gtids.html
	// https://dev.mysql.com/doc/refman/8.0/en/replication-options-gtids.html
	"gtid_mode": ParseGTIDMode,

	// https://galeracluster.com/documentation/html_docs_proto-12/documentation/mysql-wsrep-options.html#wsrep-provider-options
	"wsrep_provider_options": parseWsrepProviderOptions,
}

// ConvertGlobalStatus converts the given key and sql.RawBytes value into an appropriate type based on globalStatusConversions.
// It returns the converted value and an error if the conversion fails.
func ConvertGlobalStatus(key string, value sql.RawBytes) (interface{}, error) {
	if bytes.Equal(value, []byte("")) {
		return nil, nil
	}

	if conv, ok := globalStatusConversions[key]; ok {
		return conv(value)
	}

	return ParseValue(value)
}

// ConvertGlobalVariables converts the given key and sql.RawBytes value into an appropriate type based on globalVariableConversions.
// It returns the converted value and an error if the conversion fails.
func ConvertGlobalVariables(key string, value sql.RawBytes) (interface{}, error) {
	if bytes.Equal(value, []byte("")) {
		return nil, nil
	}

	if conv, ok := globalVariableConversions[key]; ok {
		return conv(value)
	}

	return ParseValue(value)
}