package handler

import (
	"database/sql"
	"encoding/json"
	"fmt"
	_ "github.com/go-sql-driver/mysql"
	"luwak/model"
	"net/http"
)

// 存储所有的handler函数
var handlers map[string]func(http.ResponseWriter, *http.Request)

// 存储所有的数据库连接
var connection map[string]*sql.DB

func GetTableAndColumns() []model.Table {
	var rows *sql.Rows
	tables := make(map[string]map[string][]string, 0)
	defer func() {
		if rows == nil {
			return
		}
		if err := rows.Close(); err != nil {
			panic(err)
		}
	}()
	for dbName, db := range connection {
		tables[dbName] = make(map[string][]string, 0)
		var err error
		var query string
		// 查询数据库下的所有表名和字段名
		query = "SELECT table_name, column_name FROM information_schema.columns WHERE table_schema = ?"
		rows, err = db.Query(query, dbName)
		if err != nil {
			panic(err)
		}
		for rows.Next() {
			var tableName, fieldName string
			err := rows.Scan(&tableName, &fieldName)
			if err != nil {
				panic(err)
			}
			tables[dbName][tableName] = append(tables[dbName][tableName], fieldName)
		}

		rows.Close()
	}
	return convertMapToTable(tables)
}

func convertMapToTable(table map[string]map[string][]string) []model.Table {
	var tables []model.Table
	for dbName, v := range table {
		for tableName, columns := range v {
			tables = append(tables, model.Table{
				DbName:    dbName,
				TableName: tableName,
				Columns:   columns,
			})
		}
	}
	return tables
}

// RegisterAll 注册所有的handler函数和数据库连接
func RegisterAll() {
	handlers = make(map[string]func(http.ResponseWriter, *http.Request))
	connection = make(map[string]*sql.DB)
	//模拟从redis获取表结构
	tables := []model.Table{
		{
			TableName: "user",
			Columns:   []string{"id", "name", "age"},
		},
	}
	for _, table := range tables {
		db, err := sql.Open("mysql", "root:root@tcp(127.0.0.1:3306)/"+table.TableName)
		if err != nil {
			panic(err)
		}
		connection[table.TableName] = db
		registerInsertHandler(table)
		registerQueryHandler(table)
		registerUpdateHandler(table)
		registerDeleteHandler(table)
	}
	tableAndColumns := GetTableAndColumns()
	fmt.Println(tableAndColumns)
}

// registerInsertHandler 注册一系列插入数据的处理函数
func registerInsertHandler(table model.Table) {
	handlers["/insert/"+table.TableName] = func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		//获取请求体
		body := r.Body
		defer body.Close()
		param := make([]map[string]interface{}, 0)
		//解析请求体
		err := json.NewDecoder(body).Decode(&param)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//校验请求体与表结构是否匹配
		for _, p := range param {
			if !checkParam(p, table.Columns) {
				w.WriteHeader(http.StatusBadRequest)
				return
			}
		}
		for _, p := range param {
			//按照顺序构造column和value
			columns := ""
			values := ""
			for field, value := range p {
				columns += field + ","
				values += fmt.Sprintf("'%v',", value)
			}
			columns = columns[:len(columns)-1]
			values = values[:len(values)-1]
			//构造sql语句
			execSql := fmt.Sprintf("insert into %s (%s) values (%s)", table.TableName, columns, values)
			//执行sql语句
			_, err := connection[table.TableName].Exec(execSql)
			if err != nil {
				w.WriteHeader(http.StatusInternalServerError)
				return
			}
		}
	}
}

// registerQueryHandler 注册一系列查询数据的处理函数
func registerQueryHandler(table model.Table) {
	handlers["/query/"+table.TableName] = func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		//获取请求体
		body := r.Body
		defer body.Close()
		param := make(map[string]interface{})
		//解析请求体
		err := json.NewDecoder(body).Decode(&param)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//校验请求体与表结构是否匹配
		if !checkParam(param, table.Columns) {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//按照顺序构造column和value
		where := "where"
		if len(param) == 0 {
			where = ""
		} else {
			for field, value := range param {
				where += fmt.Sprintf("%s = '%v' and", field, value)
			}
			//去掉最后一个and
			where = where[:len(where)-3]
		}
		//查询数据
		db := connection[table.TableName]
		//拼接sql语句
		querySql := fmt.Sprintf("select * from %s %s", table.TableName, where)
		rows, err := db.Query(querySql)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		//返回数据
		var result []map[string]string
		for rows.Next() {
			columns, err := rows.Columns()
			if err != nil {
				w.WriteHeader(http.StatusInternalServerError)
				return
			}
			values := make([]sql.RawBytes, len(columns))
			scanArgs := make([]interface{}, len(values))
			for i := range values {
				scanArgs[i] = &values[i]
			}
			err = rows.Scan(scanArgs...)
			if err != nil {
				w.WriteHeader(http.StatusInternalServerError)
				return
			}
			row := make(map[string]string)
			for i, col := range values {
				if col == nil {
					row[columns[i]] = ""
				} else {
					row[columns[i]] = string(col)
				}
			}
			result = append(result, row)
		}
		w.Header().Set("Content-Type", "application/json; charset=utf-8")
		bytes, err := json.Marshal(result)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		_, err = w.Write(bytes)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
	}
}

// registerUpdateHandler 注册一系列更新数据的处理函数
func registerUpdateHandler(table model.Table) {
	handlers["/update/"+table.TableName] = func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		//获取请求体
		body := r.Body
		defer body.Close()
		param := make(map[string]interface{})
		//解析请求体
		err := json.NewDecoder(body).Decode(&param)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//校验请求体与表结构是否匹配
		if !checkParam(param, table.Columns) {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		if param["where"] == nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//按照顺序构造column和value
		set := ""
		for field, value := range param {
			if field == "where" {
				continue
			}
			set += fmt.Sprintf("%s = '%v',", field, value)
		}
		//去掉最后一个逗号
		set = set[:len(set)-1]
		//构造where
		m, ok := param["where"].(map[string]interface{})
		if !ok {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		where := "where "
		for field, value := range m {
			where += fmt.Sprintf("%s = '%v' and", field, value)
		}
		//去掉最后一个and
		where = where[:len(where)-3]
		//更新数据
		db := connection[table.TableName]
		//拼接sql语句
		updateSql := fmt.Sprintf("update %s set %s %s", table.TableName, set, where)
		_, err = db.Exec(updateSql)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		w.WriteHeader(http.StatusOK)
	}
}

// registerDeleteHandler 注册一系列删除数据的处理函数
func registerDeleteHandler(table model.Table) {
	handlers["/delete/"+table.TableName] = func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		//获取请求体
		body := r.Body
		defer body.Close()
		param := make(map[string]interface{})
		//解析请求体
		err := json.NewDecoder(body).Decode(&param)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//校验请求体与表结构是否匹配
		if !checkParam(param, table.Columns) {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		//构造where
		where := "where "
		if len(param) == 0 {
			w.WriteHeader(http.StatusBadRequest)
			return
		} else {
			for field, value := range param {
				where += fmt.Sprintf("%s = '%v' and", field, value)
			}
			//去掉最后一个and
			where = where[:len(where)-3]
		}
		//删除数据
		db := connection[table.TableName]
		//拼接sql语句
		deleteSql := fmt.Sprintf("delete from %s %s", table.TableName, where)
		_, err = db.Exec(deleteSql)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		w.WriteHeader(http.StatusOK)
	}
}

func GetHandlers() map[string]func(http.ResponseWriter, *http.Request) {
	return handlers
}

func checkParam(param map[string]interface{}, cols []string) bool {
	for k := range param {
		//跳过where字段
		if k == "where" || k == "limit" || k == "offset" || k == "order" || k == "having" || k == "group" {
			continue
		}
		ok := false
		for _, col := range cols {
			if k == col {
				ok = true
				continue
			}
		}
		if !ok {
			return false
		}
	}
	return true
}