// Copyright (c) 2016 MariaDB Corporation Ab
//
// Use of this software is governed by the Business Source License included
// in the LICENSE.TXT file and at www.mariadb.com/bsl.
//
// Change Date: 2019-07-01
//
// On the date above, in accordance with the Business Source License, use
// of this software will be governed by version 2 or later of the General
// Public License.

package main

import (
	"database/sql"
	"encoding/json"
	"flag"
	"log"
	"os"
	"regexp"
	"strconv"
)

import _ "github.com/go-sql-driver/mysql"

var host = flag.String("host", "localhost", "Server address")
var port = flag.Int("port", 3306, "Server port")
var user = flag.String("user", "", "Server user")
var passwd = flag.String("password", "", "Server password")
var debug = flag.Bool("debug", false, "Debug output")

// Avro field
type Field struct {
	Name string `json:"name"`
	Type string `json:"type"`
}

// Avro schema
type Schema struct {
	Namespace string  `json:"namespace"`
	Type      string  `json:"type"`
	Name      string  `json:"name"`
	Fields    []Field `json:"fields"`
}

// Debugging output helper function
func LogObject(obj interface{}) {
	js, err := json.Marshal(obj)
	if err != nil {
		log.Fatal("Failed to parse object: ", err)
	} else {
		log.Println("Unsupported type: ", string(js))
	}
}

var field_re *regexp.Regexp

// Convert the SQL type to the appropriate Avro type
func (f *Field) ToAvroType() {
	f.Type = field_re.ReplaceAllString(f.Type, "")
	switch f.Type {
	case "date", "datetime", "time", "timestamp", "year", "tinytext", "text",
		"mediumtext", "longtext", "char", "varchar", "enum", "set":
		f.Type = "string"
	case "tinyblob", "blob", "mediumblob", "longblob", "binary", "varbinary":
		f.Type = "bytes"
	case "int", "smallint", "mediumint", "integer", "tinyint", "short",
		"decimal", "bit":
		f.Type = "int"
	case "float":
		f.Type = "float"
	case "double":
		f.Type = "double"
	case "null":
		f.Type = "null"
	case "long", "bigint":
		f.Type = "long"
	default:
		LogObject(f)
		f.Type = "string"
	}
}

// Create and store the Avro schema to disk
func StoreSchema(db *sql.DB, schema, table string) {
	file, err := os.Create(schema + "." + table + ".000001.avsc")
	if err != nil {
		log.Fatal("Failed to create file:", err)
	}
	defer file.Close()

	encoder := json.NewEncoder(file)
	fields, err := db.Query("DESCRIBE " + schema + "." + table)
	if err != nil {
		log.Fatal("Failed to query for description of "+schema+"."+table+": ", err)
	}
	defer fields.Close()

	fieldlist := make([]Field, 0, 10)

	for fields.Next() {
		var field Field
		var Null, Key, Default, Extra string

		fields.Scan(&field.Name, &field.Type, &Null, &Key, &Default, &Extra)
		field.ToAvroType()
		fieldlist = append(fieldlist, field)
	}

	encoder.Encode(Schema{Namespace: "MaxScaleChangeDataSchema.avro", Type: "record", Name: "ChangeRecord", Fields: fieldlist})
}

// Main funtion that queries the database for table names
func main() {
	var err error
	field_re, err = regexp.Compile("[(].*")
	if err != nil {
		log.Fatal("Error: ", err)
	}

	flag.Parse()

	var connect_str string = *user + ":" + *passwd + "@tcp(" + *host + ":" + strconv.Itoa(*port) + ")/"

	if *debug {
		log.Println("Connect string: ", connect_str)
	}

	db, err := sql.Open("mysql", connect_str)
	if err != nil {
		log.Fatal("Failed to open connection to", *host, *port, ":", err)
	}
	defer db.Close()

	databases, err := db.Query("SHOW DATABASES")
	if err != nil {
		log.Fatal("Failed to query for databases: ", err)
	}
	defer databases.Close()

	for databases.Next() {
		var schemaname string
		databases.Scan(&schemaname)

		// Skip the system databases
		switch schemaname {
		case "mysql", "information_schema", "performance_schema":
			continue
		}

		tables, err := db.Query("SHOW TABLES FROM " + schemaname)
		if err != nil {
			log.Fatal("Failed to query for tables from "+schemaname+": ", err)
		}
		defer tables.Close()

		for tables.Next() {
			var tablename string
			tables.Scan(&tablename)

			if *debug {
				log.Println("Processing", schemaname, ".", tablename)
			}

			StoreSchema(db, schemaname, tablename)
		}
	}
}