package engine

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strings"

	"git.fsdpf.net/go/contracts"
	"git.fsdpf.net/go/contracts/support"
	"git.fsdpf.net/go/db"
	"github.com/samber/lo"
	"github.com/spf13/cast"
)

var conn *db.Connection

func init() {
	database := db.Open(map[string]db.DBConfig{
		"condition-engine-sqlite3": {
			Driver: "sqlite3",
			File:   ":memory:",
		},
	})
	conn = database.Connection("condition-engine-sqlite3")
}

type Engine[T any] struct {
	code       string
	g          contracts.GlobalParams
	def        func(data T, g contracts.GlobalParams) error
	predicates []*EngineCase[T]
	relations  []string
}

func (this Engine[T]) GetCode() string {
	return this.code
}

// 公共参数
func (this *Engine[T]) SetGlobalParams(g contracts.GlobalParams) *Engine[T] {
	this.g = g
	return this
}

func (this *Engine[T]) Case(cond contracts.Condition, cb func(data T, g contracts.GlobalParams) error) *Engine[T] {
	this.predicates = append(this.predicates, &EngineCase[T]{cond, cb})
	return this
}

// 基础条件
func (this *Engine[T]) Default(cb func(data T, g contracts.GlobalParams) error) *Engine[T] {
	this.def = cb
	return this
}

func (this Engine[T]) toField(rv reflect.Value) (string, error) {
	if rv.Kind() == reflect.Ptr {
		rv = reflect.Indirect(rv)
	}

	if rv.IsZero() {
		return "NULL", nil
	}

	v := rv.Interface()

	switch reflect.TypeOf(v).Kind() {
	case reflect.Map, reflect.Array, reflect.Slice, reflect.Struct:
		b, err := json.Marshal(v)
		if err != nil {
			return "", err
		}
		return fmt.Sprintf("CAST('%s' AS JSON1)", b), nil
	case reflect.String:
		return fmt.Sprintf("CAST('%s' AS TEXT)", v), nil
	case reflect.Int, reflect.Int64, reflect.Int32, reflect.Int8, reflect.Int16,
		reflect.Uint, reflect.Uint64, reflect.Uint32, reflect.Uint8, reflect.Uint16:
		return fmt.Sprintf("CAST(%d AS INTEGER)", v), nil
	case reflect.Float64, reflect.Float32:
		return fmt.Sprintf("CAST(%v AS REAL)", v), nil
	case reflect.Bool:
		return fmt.Sprintf("CAST(%v AS BOOL)", v), nil
	}
	return "NULL", nil
}

func (this Engine[T]) toTables(rv reflect.Value, table string) (tables map[string][]string, err error) {
	rt := rv.Type()

	if rv.Kind() == reflect.Ptr {
		rv = reflect.Indirect(rv.Elem())
		rt = rv.Type()
	}

	if tables == nil {
		tables = map[string][]string{}
	}

	if _, ok := tables[table]; !ok {
		tables[table] = []string{}
	}

	if rv.Kind() == reflect.Struct {
		// 遍历结构体的字段
		for i := 0; i < rt.NumField(); i++ {
			if _, ok := tables[rt.Field(i).Name]; !ok && lo.Contains(this.relations, rt.Field(i).Name) {
				if items, err := this.toTables(rv.Field(i).Elem(), rt.Field(i).Name); err == nil {
					tables = lo.Assign(tables, items)
				} else {
					return nil, err
				}
			} else if s, err := this.toField(rv.Field(i)); err != nil {
				return nil, err
			} else {
				tables[table] = append(tables[table], fmt.Sprintf("%s as `%s`", s, lo.Ternary(rt.Field(i).Tag.Get("db") != "", rt.Field(i).Tag.Get("db"), rt.Field(i).Name)))
			}
		}
	} else if rv.Kind() == reflect.Map {
		iter := rv.MapRange()
		for iter.Next() {
			if _, ok := tables[iter.Key().String()]; !ok && lo.Contains(this.relations, iter.Key().String()) {
				if items, err := this.toTables(iter.Value().Elem(), iter.Key().String()); err == nil {
					tables = lo.Assign(tables, items)
				} else {
					return nil, err
				}
			} else if s, err := this.toField(iter.Value()); err != nil {
				return nil, err
			} else {
				tables[table] = append(tables[table], fmt.Sprintf("%s as `%s`", s, iter.Key().String()))
			}
		}
	} else {
		return nil, fmt.Errorf("data type not map/struct, %s", rv.Kind())
	}

	return tables, nil
}

func (this *Engine[T]) Execute(data T) error {

	tables, err := this.toTables(reflect.ValueOf(data), this.GetCode())

	if err != nil {
		return err
	}

	columns, ok := tables[this.GetCode()]

	if !ok {
		return fmt.Errorf("data is not")
	}

	sql := conn.Query().FromSub(fmt.Sprintf("SELECT %s", strings.Join(append(columns, "1 as `_`"), ", ")), this.GetCode())

	for table, columns := range lo.OmitByKeys(tables, []string{this.GetCode()}) {
		sql.JoinSub(
			fmt.Sprintf("SELECT %s", strings.Join(append(columns, "1 as `_`"), ", ")),
			table,
			fmt.Sprintf("%s._", this.GetCode()),
			fmt.Sprintf("%s._", table),
		)
	}

	if this.g == nil {
		this.g = support.NewGlobalParam(`{}`, nil)
	}

	param := &EngineParam{this.g}

	for i, p := range this.predicates {
		sql.AddSelect(db.Raw(fmt.Sprintf("IFNULL(%s, 0) as `%d`", p.ToSql(param), i)))
	}

	result := map[string]int64{}

	// fmt.Println("sql", sql.ToSql())

	if _, err := sql.First(&result); err != nil {
		return fmt.Errorf("%s => %s", err, sql.ToSql())
	}

	isDefault := true
	for k, v := range result {
		if v == 0 {
			continue
		}

		isDefault = false

		if err := this.predicates[cast.ToInt64(k)].Execute(data, this.g); err != nil {
			return fmt.Errorf("case %q error, %s", k, err)
		}
	}

	if isDefault && this.def != nil {
		if err := this.def(data, this.g); err != nil {
			return fmt.Errorf("case %q error, %s", "default", err)
		}
	}

	return nil
}

func New[T any](table string, g contracts.GlobalParams, relations ...string) *Engine[T] {
	return &Engine[T]{code: table, g: g, relations: relations}
}