// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016-2020 Datadog, Inc.

// Go MySQL Driver - A MySQL-Driver for Go's database/sql package
//
// Copyright 2014 The Go-MySQL-Driver Authors. All rights reserved.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
//
// Copied from package github.com/go-sql-driver:
// https://github.com/go-sql-driver/mysql/blob/9181e3a86a19bacd63e68d43ae8b7b36320d8092/dsn.go

package internal

import (
	"crypto/tls"
	"errors"
	"strings"
	"time"
)

const defaultCollation = "utf8_general_ci"

// A blacklist of collations which is unsafe to interpolate parameters.
// These multibyte encodings may contains 0x5c (`\`) in their trailing bytes.
var unsafeCollations = map[string]bool{
	"big5_chinese_ci":   true,
	"sjis_japanese_ci":  true,
	"gbk_chinese_ci":    true,
	"big5_bin":          true,
	"gb2312_bin":        true,
	"gbk_bin":           true,
	"sjis_bin":          true,
	"cp932_japanese_ci": true,
	"cp932_bin":         true,
}

var (
	errInvalidDSNUnescaped       = errors.New("invalid DSN: did you forget to escape a param value?")
	errInvalidDSNAddr            = errors.New("invalid DSN: network address not terminated (missing closing brace)")
	errInvalidDSNNoSlash         = errors.New("invalid DSN: missing the slash separating the database name")
	errInvalidDSNUnsafeCollation = errors.New("invalid DSN: interpolateParams can not be used with unsafe collations")
)

// Config is a configuration parsed from a DSN string
type mySQLConfig struct {
	User             string            // Username
	Passwd           string            // Password (requires User)
	Net              string            // Network type
	Addr             string            // Network address (requires Net)
	DBName           string            // Database name
	Params           map[string]string // Connection parameters
	Collation        string            // Connection collation
	Loc              *time.Location    // Location for time.Time values
	MaxAllowedPacket int               // Max packet size allowed
	TLSConfig        string            // TLS configuration name
	tls              *tls.Config       // TLS configuration
	Timeout          time.Duration     // Dial timeout
	ReadTimeout      time.Duration     // I/O read timeout
	WriteTimeout     time.Duration     // I/O write timeout

	AllowAllFiles           bool // Allow all files to be used with LOAD DATA LOCAL INFILE
	AllowCleartextPasswords bool // Allows the cleartext client side plugin
	AllowNativePasswords    bool // Allows the native password authentication method
	AllowOldPasswords       bool // Allows the old insecure password method
	ClientFoundRows         bool // Return number of matching rows instead of rows changed
	ColumnsWithAlias        bool // Prepend table alias to column names
	InterpolateParams       bool // Interpolate placeholders into query string
	MultiStatements         bool // Allow multiple statements in one query
	ParseTime               bool // Parse time values to time.Time
	Strict                  bool // Return warnings as errors
}

// mySQLConfigFromDSN parses the MySQL DSN string to a Config.
func mySQLConfigFromDSN(dsn string) (cfg *mySQLConfig, err error) {
	// New config with some default values
	cfg = &mySQLConfig{
		Loc:       time.UTC,
		Collation: defaultCollation,
	}

	// [user[:password]@][net[(addr)]]/dbname[?param1=value1&paramN=valueN]
	// Find the last '/' (since the password or the net addr might contain a '/')
	foundSlash := false
	for i := len(dsn) - 1; i >= 0; i-- {
		if dsn[i] == '/' {
			foundSlash = true
			var j, k int

			// left part is empty if i <= 0
			if i > 0 {
				// [username[:password]@][protocol[(address)]]
				// Find the last '@' in dsn[:i]
				for j = i; j >= 0; j-- {
					if dsn[j] == '@' {
						// username[:password]
						// Find the first ':' in dsn[:j]
						for k = 0; k < j; k++ {
							if dsn[k] == ':' {
								cfg.Passwd = dsn[k+1 : j]
								break
							}
						}
						cfg.User = dsn[:k]

						break
					}
				}

				// [protocol[(address)]]
				// Find the first '(' in dsn[j+1:i]
				for k = j + 1; k < i; k++ {
					if dsn[k] == '(' {
						// dsn[i-1] must be == ')' if an address is specified
						if dsn[i-1] != ')' {
							if strings.ContainsRune(dsn[k+1:i], ')') {
								return nil, errInvalidDSNUnescaped
							}
							return nil, errInvalidDSNAddr
						}
						cfg.Addr = dsn[k+1 : i-1]
						break
					}
				}
				cfg.Net = dsn[j+1 : k]
			}

			// dbname[?param1=value1&...&paramN=valueN]
			// Find the first '?' in dsn[i+1:]
			for j = i + 1; j < len(dsn); j++ {
				if dsn[j] == '?' {
					break
				}
			}
			cfg.DBName = dsn[i+1 : j]

			break
		}
	}

	if !foundSlash && len(dsn) > 0 {
		return nil, errInvalidDSNNoSlash
	}

	if cfg.InterpolateParams && unsafeCollations[cfg.Collation] {
		return nil, errInvalidDSNUnsafeCollation
	}

	// Set default network if empty
	if cfg.Net == "" {
		cfg.Net = "tcp"
	}

	// Set default address if empty
	if cfg.Addr == "" {
		switch cfg.Net {
		case "tcp":
			cfg.Addr = "127.0.0.1:3306"
		case "unix":
			cfg.Addr = "/tmp/mysql.sock"
		default:
			return nil, errors.New("default addr for network '" + cfg.Net + "' unknown")
		}

	}

	return
}
