package main

import (
	"errors"
	"fmt"
	"log"
	"strconv"
	"time"

	"github.com/google/uuid"
)

type (
	db struct {
		Knowledge knowledge
		Users     map[string]user
		Cadence   []duration
	}
	knowledge struct {
		Questions map[string]Question
		Answers   map[string]Answer
	}
	user struct {
		History map[string][]History
	}
	duration time.Duration
)

func (db db) HistoryOf(user string) map[string][]History {
	return db.Users[user].History
}

func (db db) Next(user, q string) time.Time {
	history := db.Users[user].History[q]
	progress := 0
	for i := range history {
		if history[i].Pass {
			progress += 1
		} else {
			progress -= 1
		}
	}
	if progress < 0 {
		progress = 0
	} else if progress > len(db.Cadence) {
		return time.Now().Add(time.Hour * 24 * 365 * 10)
	}
	return db.lastTS(user, q).Add(time.Duration(db.Cadence[progress]))
}

func (db db) Question(q string) Question {
	return db.Knowledge.Questions[q]
}

func (db db) LastAnswer(user, q string) Answer {
	for _, v := range db.Knowledge.Answers {
		if v.Q == q && v.Author == user {
			return v
		}
	}
	return Answer{}
}

func (db db) Answer(a string) Answer {
	return db.Knowledge.Answers[a]
}

func (db db) PushAnswer(user, q, a string, pass bool) error {
	uuid := uuid.New().String()
	db.Knowledge.Answers[uuid] = Answer{
		Q:      q,
		A:      a,
		TS:     time.Now().UnixNano(),
		Author: user,
	}
	db.Users[user].History[q] = append(db.Users[user].History[q], History{
		A:    uuid,
		Pass: pass,
	})
	return nil
}

func (db db) lastTS(user, q string) time.Time {
	max := int64(0)
	for _, v := range db.Users[user].History[q] {
		if v.TS > max {
			max = v.TS
		}
	}
	return time.Unix(0, max)
}

func (d duration) MarshalYAML() (interface{}, error) {
	log.Println("marshalling duration", time.Duration(d))
	return time.Duration(d).String(), nil
}

func (d *duration) UnmarshalYAML(unmarshal func(interface{}) error) error {
	var s string
	if err := unmarshal(&s); err != nil {
		return err
	}
	count := ""
	var ttl time.Duration
	for i := range s {
		if s[i] < '0' || s[i] > '9' {
			n, err := strconv.Atoi(count)
			if err != nil {
				return err
			}
			count += s[i : i+1]
			switch s[i] {
			case 'w':
				count = fmt.Sprintf("%dh", n*24*7)
			case 'd':
				count = fmt.Sprintf("%dh", n*24)
			}
			d, err := time.ParseDuration(count)
			if err != nil {
				return err
			}
			ttl += d
			count = ""
		} else {
			count += s[i : i+1]
		}
	}
	if count != "" {
		return errors.New(count)
	}
	*d = duration(ttl)
	return nil
}