package cassandra

import (
	"context"
	"fmt"
	"github.com/scylladb/gocqlx/v3/qb"
	"github.com/scylladb/gocqlx/v3/table"
	"reflect"
	"time"
)

func (db *DB) AutoCreateSAIIndexes(doc any, keyspace string) error {
	metadata, err := GenerateTableMetadata(doc, keyspace)
	if err != nil {
		return err
	}
	t := reflect.TypeOf(doc)
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		if f.Tag.Get("sai") == "true" {
			col := f.Tag.Get("cql")
			if col == "" {
				col = toSnakeCase(f.Name)
			}
			stmt := fmt.Sprintf("CREATE INDEX IF NOT EXISTS ON %s (%s) USING 'sai';", metadata.Name, col)
			if err := db.GetSession().ExecStmt(stmt); err != nil {
				return fmt.Errorf("SAI index create fail: %w", err)
			}
		}
	}
	return nil
}

type Query struct {
	db       *DB
	ctx      context.Context
	table    string
	keyspace string
	columns  []string
	cmps     []qb.Cmp
	bindMap  map[string]any
	orders   []orderBy
	limit    uint
	document any
	sets     []setField // 欲更新欄位及其值
}

type orderBy struct {
	Column string
	Order  qb.Order
}

type setField struct {
	Col string
	Val any
}

func (db *DB) Model(ctx context.Context, document any, keyspace string) *Query {
	metadata, _ := GenerateTableMetadata(document, keyspace)

	return &Query{
		db:       db,
		ctx:      ctx,
		table:    metadata.Name,
		keyspace: keyspace,
		columns:  make([]string, 0),
		cmps:     make([]qb.Cmp, 0),
		bindMap:  make(map[string]any),
		orders:   make([]orderBy, 0),
		limit:    0,
		document: document,
	}
}

// Where 只允許 partition key 或有 sai index 的欄位進行 where 查詢
func (q *Query) Where(cmp qb.Cmp, args map[string]any) *Query {
	metadata, _ := GenerateTableMetadata(q.document, q.keyspace)
	for k := range args {
		// 允許 partition_key 或 sai 欄位
		isPartition := contains(metadata.PartKey, k)
		isSAI := IsSAIField(q.document, k)
		if !isPartition && !isSAI {
			panic(fmt.Sprintf("field %s must be partition key or SAI index", k))
		}
		q.bindMap[k] = args[k]
	}
	q.cmps = append(q.cmps, cmp)
	for k, v := range args {
		q.bindMap[k] = v
	}

	return q
}

func (q *Query) Select(cols ...string) *Query {
	q.columns = append(q.columns, cols...)
	return q
}

func (q *Query) OrderBy(column string, order qb.Order) *Query {
	q.orders = append(q.orders, orderBy{Column: column, Order: order})
	return q
}

func (q *Query) Limit(limit uint) *Query {
	q.limit = limit

	return q
}

func (q *Query) Set(col string, val any) *Query {
	q.sets = append(q.sets, setField{Col: col, Val: val})
	return q
}

func (q *Query) Scan(dest any) error {
	builder := qb.Select(q.table)
	if len(q.columns) > 0 {
		builder = builder.Columns(q.columns...)
	}
	if len(q.cmps) > 0 {
		builder = builder.Where(q.cmps...)
	}
	if len(q.orders) > 0 {
		for _, o := range q.orders {
			builder = builder.OrderBy(o.Column, o.Order)
		}
	}
	if q.limit > 0 {
		builder = builder.Limit(q.limit)
	}

	stmt, names := builder.ToCql()
	query := q.db.GetSession().Query(stmt, names).WithContext(q.ctx)
	if q.bindMap == nil {
		q.bindMap = qb.M{}
	}
	query = query.BindMap(q.bindMap)

	return query.SelectRelease(dest)
}

func (q *Query) Take(dest any) error {
	q.limit = 1
	return q.Scan(dest)
}

func (q *Query) Delete() error {
	// 拿 partition key 清單
	metadata, err := GenerateTableMetadata(q.document, q.keyspace)
	if err != nil {
		return err
	}
	missingKeys := make([]string, 0)
	for _, pk := range metadata.PartKey {
		if _, ok := q.bindMap[pk]; !ok {
			missingKeys = append(missingKeys, pk)
		}
	}
	if len(missingKeys) > 0 {
		return fmt.Errorf("delete operation requires all partition keys in WHERE: missing %v", missingKeys)
	}
	if len(q.cmps) == 0 {
		return fmt.Errorf("delete operation requires at least one WHERE condition for safety")
	}

	// 組 Delete 語句
	builder := qb.Delete(q.table)
	builder = builder.Where(q.cmps...)
	stmt, names := builder.ToCql()
	query := q.db.GetSession().Query(stmt, names).WithContext(q.ctx)
	if q.bindMap == nil {
		q.bindMap = qb.M{}
	}
	query = query.BindMap(q.bindMap)

	return query.ExecRelease()
}

func (q *Query) Update() error {
	if q.document == nil {
		return fmt.Errorf("update requires modelType to check partition keys")
	}

	metadata, err := GenerateTableMetadata(q.document, q.keyspace)
	if err != nil {
		return fmt.Errorf("update: failed to get table metadata: %w", err)
	}

	// 檢查 partition key 是否都在 bindMap
	missingKeys := make([]string, 0)
	for _, pk := range metadata.PartKey {
		if _, ok := q.bindMap[pk]; !ok {
			missingKeys = append(missingKeys, pk)
		}
	}
	if len(missingKeys) > 0 {
		return fmt.Errorf("update operation requires all partition keys in WHERE: missing %v", missingKeys)
	}

	// 至少要有一個 set 欄位
	if len(q.sets) == 0 {
		return fmt.Errorf("update requires at least one field to set")
	}
	// 至少一個 where
	if len(q.cmps) == 0 {
		return fmt.Errorf("update operation requires at least one WHERE condition for safety")
	}

	// 組合 set 欄位
	setCols := make([]string, 0, len(q.sets))
	setVals := make([]any, 0, len(q.sets))
	for _, s := range q.sets {
		setCols = append(setCols, s.Col)
		setVals = append(setVals, s.Val)
	}

	// 組合 CQL
	builder := qb.Update(q.table).Set(setCols...)
	builder = builder.Where(q.cmps...)
	stmt, names := builder.ToCql()

	// setVals 要先，剩下的 where bind 順序依照 names
	bindVals := append([]any{}, setVals...)
	for _, name := range names[len(setCols):] {
		if v, ok := q.bindMap[name]; ok {
			bindVals = append(bindVals, v)
		}
	}

	query := q.db.GetSession().Query(stmt, names).WithContext(q.ctx)
	if len(bindVals) > 0 {
		query = query.Bind(bindVals...)
	}
	return query.ExecRelease()
}

func (q *Query) InsertOne(data any) error {
	metadata, err := GenerateTableMetadata(q.document, q.keyspace)
	if err != nil {
		return err
	}
	tbl := table.New(metadata)
	qry := q.db.GetSession().Query(tbl.Insert()).WithContext(q.ctx).WithTimestamp(time.Now().UnixNano() / 1e3)

	switch reflect.TypeOf(data).Kind() {
	case reflect.Map:
		qry = qry.BindMap(data.(map[string]any))
	default:
		qry = qry.BindStruct(data)
	}
	return qry.ExecRelease()
}

func (q *Query) InsertMany(documents any) error {
	v := reflect.ValueOf(documents)
	if v.Kind() != reflect.Slice {
		return fmt.Errorf("InsertMany: input must be a slice")
	}
	if v.Len() == 0 {
		return nil
	}

	for i := 0; i < v.Len(); i++ {
		item := v.Index(i).Interface()
		if err := q.InsertOne(item); err != nil {
			return fmt.Errorf("InsertMany: failed at idx %d: %w", i, err)
		}
	}
	return nil
}

func (q *Query) GetAll(dest any) error {
	metadata, err := GenerateTableMetadata(q.document, q.keyspace)
	if err != nil {
		return err
	}
	t := table.New(metadata)

	stmt, names := qb.Select(t.Name()).Columns(metadata.Columns...).ToCql()
	exec := q.db.GetSession().Query(stmt, names).WithContext(q.ctx).WithTimestamp(time.Now().UnixNano() / 1e3)

	return exec.SelectRelease(dest)
}

func (q *Query) Count() (int64, error) {
	metadata, err := GenerateTableMetadata(q.document, q.keyspace)
	if err != nil {
		return 0, err
	}

	t := table.New(metadata)
	builder := qb.Select(t.Name()).Columns("COUNT(*)")
	if len(q.cmps) > 0 {
		builder = builder.Where(q.cmps...)
	}

	stmt, names := builder.ToCql()
	query := q.db.GetSession().Query(stmt, names).WithContext(q.ctx).WithTimestamp(time.Now().UnixNano() / 1e3)
	if q.bindMap == nil {
		q.bindMap = qb.M{}
	}
	query = query.BindMap(q.bindMap)

	var count int64
	if err := query.GetRelease(&count); err != nil {
		return 0, err
	}
	return count, nil
}

func IsSAIField(model any, fieldName string) bool {
	t := reflect.TypeOf(model)
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		tag := f.Tag.Get("sai")
		col := f.Tag.Get("db")
		if col == "" {
			col = toSnakeCase(f.Name)
		}
		if (col == fieldName || f.Name == fieldName) && tag == "true" {
			return true
		}
	}
	return false
}