package statement

import (
	"github.com/genjidb/genji/internal/database"
	"github.com/genjidb/genji/internal/errors"
	"github.com/genjidb/genji/internal/expr"
	"github.com/genjidb/genji/internal/stream"
)

// InsertStmt holds INSERT configuration.
type InsertStmt struct {
	basePreparedStatement

	TableName  string
	Values     []expr.Expr
	Fields     []string
	SelectStmt Preparer
	Returning  []expr.Expr
	OnConflict database.OnConflictAction
}

func NewInsertStatement() *InsertStmt {
	var p InsertStmt

	p.basePreparedStatement = basePreparedStatement{
		Preparer: &p,
		ReadOnly: false,
	}

	return &p
}

func (stmt *InsertStmt) Prepare(c *Context) (Statement, error) {
	var s *stream.Stream

	if stmt.Values != nil {
		s = stream.New(stream.Expressions(stmt.Values...))
	} else {
		selectStream, err := stmt.SelectStmt.Prepare(c)
		if err != nil {
			return nil, err
		}

		s = selectStream.(*PreparedStreamStmt).Stream

		// ensure we are not reading and writing to the same table.
		// TODO(asdine): if same table, write content to a temp table.
		if tableScan, ok := s.First().(*stream.TableScanOperator); ok && tableScan.TableName == stmt.TableName {
			return nil, errors.New("cannot read and write to the same table")
		}

		if len(stmt.Fields) > 0 {
			s = s.Pipe(stream.IterRename(stmt.Fields...))
		}
	}

	// validate document
	s = s.Pipe(stream.TableValidate(stmt.TableName))

	if stmt.OnConflict != 0 {
		switch stmt.OnConflict {
		case database.OnConflictDoNothing:
			s = s.Pipe(stream.HandleConflict(stream.New(stream.NoOp())))
		case database.OnConflictDoReplace:
			s = s.Pipe(stream.HandleConflict(stream.New(stream.TableReplace(stmt.TableName))))
		default:
			panic("unreachable")
		}
	}

	// check unique constraints
	indexNames := c.Catalog.ListIndexes(stmt.TableName)
	for _, indexName := range indexNames {
		info, err := c.Catalog.GetIndexInfo(indexName)
		if err != nil {
			return nil, err
		}

		if info.Unique {
			s = s.Pipe(stream.IndexValidate(indexName))
		}
	}

	s = s.Pipe(stream.TableInsert(stmt.TableName))

	for _, indexName := range indexNames {
		s = s.Pipe(stream.IndexInsert(indexName))
	}

	if len(stmt.Returning) > 0 {
		s = s.Pipe(stream.Project(stmt.Returning...))
	}

	st := StreamStmt{
		Stream:   s,
		ReadOnly: false,
	}

	return st.Prepare(c)
}