package sqlgen

import (
	"errors"
	"os"
	"strings"
)

func parsePath(filePath string) (*schema, error) {
	fileBytes, err := os.ReadFile(filePath)
	if err != nil {
		return nil, err
	}
	return parseBytes(fileBytes)
}

func parseBytes(fileBytes []byte) (*schema, error) {
	s := string(fileBytes)
	for _, c := range []string{",", "(", ")", ";"} {
		s = strings.ReplaceAll(s, c, " "+c+" ")
	}

	var (
		tokens = strings.Fields(s)
		schema = &schema{}
		err    error
	)

	for len(tokens) > 0 {
		switch tokens[0] {
		case "TABLE":
			tokens, err = parseTable(schema, tokens)
			if err != nil {
				return nil, err
			}

		default:
			return nil, errors.New("invalid token: " + tokens[0])
		}
	}

	return schema, nil
}

func parseTable(schema *schema, tokens []string) ([]string, error) {
	tokens = tokens[1:]
	if len(tokens) < 3 {
		return tokens, errors.New("incomplete table definition")
	}
	if tokens[1] != "OF" {
		return tokens, errors.New("expected OF in table definition")
	}

	table := &table{
		Name: tokens[0],
		Type: tokens[2],
	}
	schema.Tables = append(schema.Tables, table)

	tokens = tokens[3:]

	if len(tokens) == 0 {
		return tokens, errors.New("missing table definition body")
	}

	for len(tokens) > 0 {
		switch tokens[0] {
		case "NoInsert":
			table.NoInsert = true
			tokens = tokens[1:]
		case "NoUpdate":
			table.NoUpdate = true
			tokens = tokens[1:]
		case "NoDelete":
			table.NoDelete = true
			tokens = tokens[1:]
		case "(":
			return parseTableBody(table, tokens[1:])
		default:
			return tokens, errors.New("unexpected token in table definition: " + tokens[0])
		}
	}

	return tokens, errors.New("incomplete table definition")
}

func parseTableBody(table *table, tokens []string) ([]string, error) {
	var err error

	for len(tokens) > 0 && tokens[0] != ";" {
		tokens, err = parseTableColumn(table, tokens)
		if err != nil {
			return tokens, err
		}
	}

	if len(tokens) < 1 || tokens[0] != ";" {
		return tokens, errors.New("incomplete table column definitions")
	}

	return tokens[1:], nil
}

func parseTableColumn(table *table, tokens []string) ([]string, error) {
	if len(tokens) < 2 {
		return tokens, errors.New("incomplete column definition")
	}
	column := &column{
		Name:    tokens[0],
		Type:    tokens[1],
		SqlName: tokens[0],
	}
	table.Columns = append(table.Columns, column)

	tokens = tokens[2:]
	for len(tokens) > 0 && tokens[0] != "," && tokens[0] != ")" {
		switch tokens[0] {
		case "AS":
			if len(tokens) < 2 {
				return tokens, errors.New("incomplete AS clause in column definition")
			}
			column.Name = tokens[1]
			tokens = tokens[2:]
		case "PK":
			column.PK = true
			tokens = tokens[1:]
		case "NoInsert":
			column.NoInsert = true
			tokens = tokens[1:]
		case "NoUpdate":
			column.NoUpdate = true
			tokens = tokens[1:]
		default:
			return tokens, errors.New("unexpected token in column definition: " + tokens[0])
		}
	}

	if len(tokens) == 0 {
		return tokens, errors.New("incomplete column definition")
	}

	return tokens[1:], nil
}