package sql

import (
	"fmt"
	"slices"
)

func (p *Parser) parseCreateTable() (*CreateTableStatement, error) {
	if !p.expectNext(TABLE) {
		return nil, p.unexpectedToken()
	}

	tok, ok := p.expectOne(QUOTE, SINGLE_QUOTE, BACKQUOTE, IDENT, IF)
	if !ok {
		return nil, p.unexpectedToken(IDENT, IF)
	}

	switch tok {
	case IF:
		if !p.expectSequence(NOT, EXISTS) {
			return nil, p.unexpectedToken()
		}
		p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
		fallthrough
	case QUOTE, SINGLE_QUOTE, BACKQUOTE:
		if !p.expectNext(IDENT) {
			return nil, p.unexpectedToken()
		}
	}
	_, _, lit := p.rescan()

	stmt := CreateTableStatement{
		TableName: lit,
		Columns:   make([]Column, 0),
	}

	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
	if !p.expectNext(LPAREN) {
		return nil, p.unexpectedToken(LPAREN)
	}

	for {
		p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
		_, tok, _ := p.scan()

		switch tok {
		case RPAREN:
			if !p.expectNext(SEMI) {
				return nil, p.unexpectedToken(SEMI)
			}
			return &stmt, nil

		case IDENT:
			column, err := p.parseColumn()
			if err != nil {
				return nil, err
			}
			stmt.Columns = append(stmt.Columns, column)

		// TODO: HANDLE AND SAVE CONSTRAINTS
		case CONSTRAINT:
			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
			if !p.expectNext(IDENT) {
				return nil, p.unexpectedToken()
			}
			// _, _, constraintName := p.rescan()
			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

		case FOREIGN:
			if !p.expectSequence(KEY, LPAREN) {
				return nil, p.unexpectedToken()
			}

			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

			if !p.expectNext(IDENT) {
				return nil, p.unexpectedToken()
			}
			_, _, columnName := p.rescan()

			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

			if !p.expectSequence(RPAREN, REFERENCES) {
				return nil, p.unexpectedToken()
			}

			ref, err := p.references()
			if err != nil {
				return nil, err
			}

			column := slices.IndexFunc(stmt.Columns, func(c Column) bool {
				return c.Name == columnName
			})

			stmt.Columns[column].Extra = append(stmt.Columns[column].Extra, ref)

		case PRIMARY:
			if !p.expectSequence(KEY, LPAREN) {
				return nil, p.unexpectedToken()
			}
			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

			if !p.expectNext(IDENT) {
				return nil, p.unexpectedToken()
			}

			primaryKeyNames := make([]string, 0)
			_, _, columnName := p.rescan()
			primaryKeyNames = append(primaryKeyNames, columnName)
			p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

			for {
				tok, ok := p.expectOne(RPAREN, COMMA)
				if !ok {
					return nil, p.unexpectedToken()
				}
				if tok == RPAREN {
					break
				}

				p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
				if !p.expectNext(IDENT) {
					return nil, p.unexpectedToken()
				}

				_, _, columnName := p.rescan()

				p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
				primaryKeyNames = append(primaryKeyNames, columnName)
			}

			for _, pkName := range primaryKeyNames {
				column := slices.IndexFunc(stmt.Columns, func(c Column) bool {
					return c.Name == pkName
				})
				stmt.Columns[column].Extra = append(stmt.Columns[column].Extra, "PRIMARY_KEY")
			}

		case COMMA:
			continue

		default:
			return nil, p.unexpectedToken(IDENT, RPAREN, FOREIGN, COMMA)
		}
	}
}

func (p *Parser) parseColumn() (Column, error) {
	_, _, lit := p.rescan()
	column := Column{Name: lit, Extra: make([]string, 0)}
	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

	if _, ok := p.expectOne(TEXT, INTEGER, REAL, BLOB, NUMERIC); !ok {
		return Column{}, p.unexpectedToken(TEXT, INTEGER, REAL, BLOB, NUMERIC)
	}
	_, _, column.Type = p.rescan()

	for {
		_, tok, lit := p.scan()
		switch tok {
		case COMMA:
			return column, nil
		case RPAREN:
			p.unscan()
			return column, nil

		case PRIMARY:
			fallthrough
		case NOT:
			if _, ok := p.expectOne(NULL, KEY); !ok {
				return Column{}, p.unexpectedToken(NULL, KEY)
			}
			_, _, rlit := p.rescan()
			column.Extra = append(column.Extra, fmt.Sprintf("%v_%v", lit, rlit))

		case REFERENCES:
			ref, err := p.references()
			if err != nil {
				return Column{}, err
			}
			column.Extra = append(column.Extra, ref)

		case AUTOINCREMENT:
			column.Extra = append(column.Extra, "AUTOINCREMENT")

		default:
			return Column{}, p.unexpectedToken(COMMA, RPAREN, PRIMARY, NOT, REFERENCES)
		}
	}
}

func (p *Parser) references() (string, error) {
	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)
	if !p.expectNext(IDENT) {
		return "", p.unexpectedToken(IDENT)
	}
	_, _, referenceTableName := p.rescan()
	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

	if !p.expectNext(LPAREN) {
		return "", p.unexpectedToken()
	}

	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

	if !p.expectNext(IDENT) {
		return "", p.unexpectedToken()
	}
	_, _, referenceColumnName := p.rescan()

	p.consumeIfOne(QUOTE, SINGLE_QUOTE, BACKQUOTE)

	if !p.expectNext(RPAREN) {
		return "", p.unexpectedToken(RPAREN)
	}

	return fmt.Sprintf("ref %v.%v", referenceTableName, referenceColumnName), nil
}