package coursed

import (
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/BurntSushi/toml"
)

var (
	ErrNoCurrentCourse = errors.New("error: no current course was found")
)

// `Schedule` represents a set of courses that the user is taking
//
// It stores this as a mapping between the course's short code, and the actual
// information about the course
type Schedule struct {
	Courses map[string]CourseConfig
}

// `CurrentCourse` returns the current course for the user, based on the
// current time, and the schedule that they defined
//
// It is assumed courses cannot overlap, so this will never return multiple
// possible courses
//
// If no course is found, the error will be of type `ErrNoCurrentCourse`
func (s Schedule) CurrentCourse() (string, error) {
	currentTime, err := time.Parse(time.Kitchen, time.Now().Format(time.Kitchen))
	if err != nil {
		return "", err
	}

	for courseName, courseInfo := range s.Courses {
		// Skip times that are TBD
		if courseInfo.StartTime == "TBD" || courseInfo.EndTime == "TBD" {
			continue
		}

		startTime, err := time.Parse(time.Kitchen, courseInfo.StartTime)
		if err != nil {
			return "", err
		}

		endTime, err := time.Parse(time.Kitchen, courseInfo.EndTime)
		if err != nil {
			return "", err
		}

		if currentTime.After(startTime) && currentTime.Before(endTime) {
			return courseName, nil
		}
	}

	return "", ErrNoCurrentCourse
}

// `CourseConfig` represents all the information that is needed about a single
// course to place it on the schedule
type CourseConfig struct {
	StartTime string `toml:"start_time"`
	EndTime   string `toml:"end_time"`
	Days      string `toml:"days"`
}

func (c CourseConfig) String() string {
	return fmt.Sprintf("CourseConfig { start: %v, end: %v, days: %v }", c.StartTime, c.EndTime, c.Days)
}

// `LoadSchedule` loads a course schedule from the given file, and returns a
// `Schdule` object containing the parsed schedule
func LoadSchedule(fileName string) (Schedule, error) {
	var v Schedule

	configFile, err := os.Open(fileName)
	if err != nil {
		return v, err
	}
	defer configFile.Close()

	if _, err := toml.NewDecoder(configFile).Decode(&v); err != nil {
		return v, err
	}

	return v, nil
}