package mysql

import (
	"fmt"
	"regexp"

	"github.com/grafana/grafana/pkg/tsdb"
)

//const rsString = `(?:"([^"]*)")`;
const rsIdentifier = `([_a-zA-Z0-9]+)`
const sExpr = `\$` + rsIdentifier + `\(([^\)]*)\)`

type SqlMacroEngine interface {
	Interpolate(sql string) (string, error)
}

type MySqlMacroEngine struct {
	TimeRange *tsdb.TimeRange
}

func NewMysqlMacroEngine(timeRange *tsdb.TimeRange) SqlMacroEngine {
	return &MySqlMacroEngine{
		TimeRange: timeRange,
	}
}

func (m *MySqlMacroEngine) Interpolate(sql string) (string, error) {
	rExp, _ := regexp.Compile(sExpr)
	var macroError error

	sql = ReplaceAllStringSubmatchFunc(rExp, sql, func(groups []string) string {
		res, err := m.EvaluateMacro(groups[1], groups[2:])
		if err != nil && macroError == nil {
			macroError = err
			return "macro_error()"
		}
		return res
	})

	if macroError != nil {
		return "", macroError
	}

	return sql, nil
}

func ReplaceAllStringSubmatchFunc(re *regexp.Regexp, str string, repl func([]string) string) string {
	result := ""
	lastIndex := 0

	for _, v := range re.FindAllSubmatchIndex([]byte(str), -1) {
		groups := []string{}
		for i := 0; i < len(v); i += 2 {
			groups = append(groups, str[v[i]:v[i+1]])
		}

		result += str[lastIndex:v[0]] + repl(groups)
		lastIndex = v[1]
	}

	return result + str[lastIndex:]
}

func (m *MySqlMacroEngine) EvaluateMacro(name string, args []string) (string, error) {
	switch name {
	case "__time":
		if len(args) == 0 {
			return "", fmt.Errorf("missing time column argument for macro %v", name)
		}
		return fmt.Sprintf("UNIX_TIMESTAMP(%s) as time_sec", args[0]), nil
	case "__timeFilter":
		if len(args) == 0 {
			return "", fmt.Errorf("missing time column argument for macro %v", name)
		}
		return fmt.Sprintf("UNIX_TIMESTAMP(%s) > %d AND UNIX_TIMESTAMP(%s) < %d", args[0], uint64(m.TimeRange.GetFromAsMsEpoch()/1000), args[0], uint64(m.TimeRange.GetToAsMsEpoch()/1000)), nil
	default:
		return "", fmt.Errorf("Unknown macro %v", name)
	}
}