package txt

import (
	"strings"
	"time"
)

// DateFromFilePath returns a string as time or the zero time instant in case it can not be converted.
func DateFromFilePath(s string) (result time.Time) {
	defer func() {
		if r := recover(); r != nil {
			result = time.Time{}
		}
	}()

	if len(s) < 6 {
		return time.Time{}
	}

	if !strings.HasPrefix(s, "/") {
		s = "/" + s
	}

	b := []byte(s)

	if found := DateTimeRegexp.Find(b); len(found) > 0 { // Is it a date with time like "2020-01-30_09-57-18"?
		n := DateIntRegexp.FindAll(found, -1)

		if len(n) < 6 {
			return result
		}

		year := ExpandYear(string(n[0]))
		month := Int(string(n[1]))
		day := Int(string(n[2]))
		hour := Int(string(n[3]))
		min := Int(string(n[4]))
		sec := Int(string(n[5]))

		// Perform date plausibility check.
		if year < YearMin || year > YearMax || month < MonthMin || month > MonthMax || day < DayMin || day > DayMax {
			return result
		}

		// Perform time plausibility check.
		if hour < HourMin || hour > HourMax || min < MinMin || min > MinMax || sec < SecMin || sec > SecMax {
			return result
		}

		result = time.Date(
			year,
			time.Month(month),
			day,
			hour,
			min,
			sec,
			0,
			time.UTC)

	} else if found = DateRegexp.Find(b); len(found) > 0 { // Is it a date only like "2020-01-30"?
		n := DateIntRegexp.FindAll(found, -1)

		if len(n) != 3 {
			return result
		}

		year := ExpandYear(string(n[0]))
		month := Int(string(n[1]))
		day := Int(string(n[2]))

		// Perform date plausibility check.
		if year < YearMin || year > YearMax || month < MonthMin || month > MonthMax || day < DayMin || day > DayMax {
			return result
		}

		result = time.Date(
			year,
			time.Month(month),
			day,
			0,
			0,
			0,
			0,
			time.UTC)
	} else if found = DatePathRegexp.Find(b); len(found) > 0 { // Is it a date path like "2020/01/03"?
		n := DateIntRegexp.FindAll(found, -1)

		if len(n) < 2 || len(n) > 3 {
			return result
		}

		year := ExpandYear(string(n[0]))
		month := Int(string(n[1]))

		if year < YearMin || year > YearMax || month < MonthMin || month > MonthMax {
			return result
		}

		if len(n) == 2 {
			result = time.Date(
				year,
				time.Month(month),
				1,
				0,
				0,
				0,
				0,
				time.UTC)
		} else if day := Int(string(n[2])); day >= DayMin && day <= DayMax {
			result = time.Date(
				year,
				time.Month(month),
				day,
				0,
				0,
				0,
				0,
				time.UTC)
		}
	}

	return result.UTC()
}
