package ticket

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"
)

var (
	reHourMin  = regexp.MustCompile(`(?i)^(\d+)\s*h(?:ours?)?\s*(\d+)\s*m(?:ins?)?$`)
	reHourOnly = regexp.MustCompile(`(?i)^(\d+(?:\.\d+)?)\s*h(?:ours?)?$`)
	reMinOnly  = regexp.MustCompile(`(?i)^(\d+)\s*m(?:ins?)?$`)
	reSecOnly  = regexp.MustCompile(`(?i)^(\d+)\s*s(?:ecs?)?$`)
	reColon    = regexp.MustCompile(`^(\d+):(\d{1,2})$`)
)

// ParseDurationFlexible parses user durations like 1h30m, 90m, 1.5h, 1:30.
func ParseDurationFlexible(s string) (time.Duration, error) {
	s = strings.TrimSpace(s)
	if s == "" {
		return 0, fmt.Errorf("duration required")
	}
	// Prefer Go's parser when it works (e.g. 1h30m, 90m).
	if d, err := time.ParseDuration(strings.ToLower(s)); err == nil && d > 0 {
		return d, nil
	}

	if m := reHourMin.FindStringSubmatch(s); m != nil {
		h, _ := strconv.Atoi(m[1])
		min, _ := strconv.Atoi(m[2])
		return time.Duration(h)*time.Hour + time.Duration(min)*time.Minute, nil
	}
	if m := reHourOnly.FindStringSubmatch(s); m != nil {
		h, err := strconv.ParseFloat(m[1], 64)
		if err != nil {
			return 0, fmt.Errorf("invalid duration %q", s)
		}
		return time.Duration(h * float64(time.Hour)), nil
	}
	if m := reMinOnly.FindStringSubmatch(s); m != nil {
		min, _ := strconv.Atoi(m[1])
		return time.Duration(min) * time.Minute, nil
	}
	if m := reSecOnly.FindStringSubmatch(s); m != nil {
		sec, _ := strconv.Atoi(m[1])
		return time.Duration(sec) * time.Second, nil
	}
	if m := reColon.FindStringSubmatch(s); m != nil {
		h, _ := strconv.Atoi(m[1])
		min, _ := strconv.Atoi(m[2])
		if min >= 60 {
			return 0, fmt.Errorf("invalid minutes in %q", s)
		}
		return time.Duration(h)*time.Hour + time.Duration(min)*time.Minute, nil
	}
	return 0, fmt.Errorf("invalid duration %q (try 1h30m, 90m, 1.5h)", s)
}