query-interpreter/q/parse.go

package q

import (
	"fmt"
	"strings"

	"github.com/DataDog/go-sqllexer"
)

// Find first token in array that matches condition
func FindTokenInArray(tokens []Token, condition func(Token) bool) (*Token, int) {
	for i, element := range tokens {
		if condition(element) {
			return &element, i
		}
	}
	return nil, -1
}

type Token = sqllexer.Token

type parser struct {
	sql              string
	tokens           []Token
	index            int
	query            Query
	lookBehindBuffer []Token
}

func (p *parser) lookAhead(count int) Token {
	return p.tokens[p.index+count]
}

func (p *parser) lookBehind(count int) Token {
	return p.tokens[p.index-count]
}

// Returns pointer of the first found Token and its index in parser.Tokens
// Returns -1 as the index if not found
func (p *parser) findToken(condition func(Token) bool) (*Token, int) {
	for i, element := range p.tokens {
		if condition(element) {
			return &element, i
		}
	}
	return nil, -1
}

type FoundToken struct {
	Token Token
	Index int
}

// Returns all tokens that match the condition, along with their indices
func (p *parser) findAllTokens(condition func(Token) bool) []FoundToken {
	matches := make([]FoundToken, 0)

	for i, token := range p.tokens {
		if condition(token) {
			matches = append(matches, FoundToken{
				Token: token,
				Index: i,
			})
		}
	}

	return matches
}

func filter[T any](items []T, fn func(item T) bool) []T {
	filteredItems := []T{}
	for _, value := range items {
		if fn(value) {
			filteredItems = append(filteredItems, value)
		}
	}
	return filteredItems
}

func unshiftBuffer(buf *[10]sqllexer.Token, value sqllexer.Token) {
	for i := 9; i >= 1; i-- {
		buf[i] = buf[i-1]
	}

	buf[0] = value
}

func Parse(sql string) (Query, error) {
	lexer := sqllexer.New(sql)

	var tokens []Token
	for {
		t := lexer.Scan()
		tokens = append(tokens, *t)

		if IsTokenEndOfStatement(t) {
			break
		}
	}

	p := parser{
		sql:    sql,
		tokens: tokens,
	}

	queryType, err := findQueryType(&p)
	if err != nil {
		return p.query, err
	}

	switch strings.ToUpper(queryType) {
	case "SELECT":
		p.query = &Select{
			Type: SELECT,
		}
		parseSelectStatement(&p)
	default:
		return p.query, fmt.Errorf("No process defined for determined queryType: %s", queryType)
	}

	return p.query, nil
}

func findQueryType(p *parser) (string, error) {
	firstCommand, _ := p.findToken(func(t Token) bool {
		return t.Type == sqllexer.COMMAND
	})

	if firstCommand == nil {
		return "", fmt.Errorf("Could not find query type")
	}

	return firstCommand.Value, nil
}

func GetFullStringFromColumn(column Column) string {
	var workingSlice string

	if column.AggregateFunction > 0 {
		workingSlice = fmt.Sprintf(
			"%s(%s)",
			AggregateFunctionTypeString(column.AggregateFunction),
			column.Name,
		)
	} else {
		workingSlice = column.Name
	}

	if column.Alias != "" {
		workingSlice += fmt.Sprintf(" AS %s", column.Alias)
	}

	return workingSlice

}

func (q *Select) GetFullSql() string {
	var workingSqlSlice []string

	workingSqlSlice = append(workingSqlSlice, "SELECT")

	if q.IsWildcard {
		workingSqlSlice = append(workingSqlSlice, "*")
	} else {
		for i, column := range q.Columns {
			if i < (len(q.Columns) - 1) {
				workingSqlSlice = append(workingSqlSlice, GetFullStringFromColumn(column)+",")
			} else {
				workingSqlSlice = append(workingSqlSlice, GetFullStringFromColumn(column))
			}
		}
	}

	workingSqlSlice = append(workingSqlSlice, "FROM "+q.Table.Name) // TODO: figure out what to do from alias

	for _, condition := range q.Conditionals {
		workingSqlSlice = append(workingSqlSlice, condition.Key)
		workingSqlSlice = append(workingSqlSlice, condition.Operator)
		workingSqlSlice = append(workingSqlSlice, condition.Value)
	}

	fullSql := strings.Join(workingSqlSlice, " ")

	return fullSql
}