package main

import (
	"context"
	"database/sql"
	_ "embed"
	"encoding/json"
	"fmt"
	"maps"
	"math/rand"
	"slices"
	"strings"
	"time"

	"github.com/google/uuid"
)

type Games struct {
	db DB
}

func NewGames(ctx context.Context, db DB) (Games, error) {
	err := db.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS users (
			uuid TEXT,
			updated DATETIME,
			name TEXT
		);
		CREATE TABLE IF NOT EXISTS games (
			uuid TEXT,
			updated DATETIME,
			name TEXT,
			completed DATETIME
		);
		CREATE TABLE IF NOT EXISTS players (
			user_uuid TEXT,
			game_uuid TEXT,
			updated DATETIME
		);
		CREATE TABLE IF NOT EXISTS events (
			game_uuid TEXT,
			timestamp DATETIME,
			payload TEXT
		);
	`)
	return Games{db: db}, err
}

func (games Games) GamesForUser(ctx context.Context, id string) ([]string, error) {
	result := []string{}
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		var game string
		err := rows.Scan(&game)
		result = append(result, game)
		return err
	}, `
		SELECT players.game_uuid
		FROM players
		WHERE players.user_uuid=?
	`, id)
	return result, err
}

func (games Games) UpdateUserName(ctx context.Context, id, name string) error {
	var n int
	if err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&n)
	}, `SELECT COUNT(uuid) FROM users WHERE uuid=?`, id); err != nil {
		return err
	}
	if n > 0 {
		return games.db.Exec(ctx, `UPDATE users SET name=? WHERE uuid=?`, name, id)
	}
	return games.db.Exec(ctx, `INSERT INTO users (uuid, name) VALUES (?, ?)`, id, name)
}

//go:embed adjectives.txt
var namesAdjectives string

//go:embed animals.txt
var namesAnimals string

func (games Games) UserName(ctx context.Context, id string) (string, error) {
	result := ""
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&result)
	}, `
		SELECT users.name
		FROM users
		WHERE users.uuid=?
	`, id)
	if result == "" {
		adjectives := strings.Fields(namesAdjectives)
		animals := strings.Split(namesAnimals, "\n")
		animals = slices.DeleteFunc(animals, func(s string) bool { return s == "" })
		name := strings.Title(fmt.Sprintf("%s %s", adjectives[rand.Intn(len(adjectives))], animals[rand.Intn(len(animals))]))
		if err := games.UpdateUserName(ctx, id, name); err != nil {
			return "", err
		}
		return games.UserName(ctx, id)
	}
	return result, err
}

func (games Games) UserByName(ctx context.Context, gid, name string) (string, error) {
	result := ""
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&result)
	}, `
		SELECT users.uuid
      FROM players
      JOIN users ON players.user_uuid=users.uuid
		WHERE players.game_uuid=? AND users.name=?
	`, gid, name)
	return result, err
}

func (a KillWord) Empty() bool {
	return a == (KillWord{})
}

func (a Assignment) Empty() bool {
	return len(a.Public) == 0 && len(a.Private) == 0
}

func (s PlayerState) Empty() bool {
	return len(s.Kills) == 0 && s.KillWords.Empty()
}

func (s PlayerState) Points() int {
	points := 0
	for _, kill := range s.Kills {
		points += kill.KillWord.Points
	}
	return points
}

func (games Games) GameName(ctx context.Context, id string) (string, error) {
	var result string
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&result)
	}, `
		SELECT
			games.name
		FROM
			games
		WHERE games.uuid=?
		ORDER BY games.updated DESC
		LIMIT 1
	`, id)
	return result, err
}

func (games Games) GameByName(ctx context.Context, name string) (string, error) {
	var result string
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&result)
	}, `
		SELECT
			games.uuid
		FROM
			games
		WHERE games.name=?
		ORDER BY games.updated DESC
		LIMIT 1
	`, name)
	return result, err
}

type (
	GameState struct {
		Started   bool
		Completed time.Time
		Players   map[string]PlayerState
	}

	PlayerState struct {
		Kills     []Kill
		KillWords KillWords
	}

	Kill struct {
		Timestamp time.Time
		Victim    string
		KillWord  KillWord
	}

	KillWords struct {
		Global KillWord

		Assigned time.Time
		Assignee string

		Assignment Assignment
	}

	Assignment struct {
		Public  []KillWord
		Private []KillWord
	}

	KillWord struct {
		Word   string
		Points int
	}

	EventType int

	EventPlayerJoin struct {
		Type      EventType
		Timestamp time.Time
		ID        string
	}
	EventPlayerLeave struct {
		Type      EventType
		Timestamp time.Time
		ID        string
	}
	EventGameComplete struct {
		Type      EventType
		Timestamp time.Time
	}
	EventAssignmentRotation struct {
		Type         EventType
		Timestamp    time.Time
		Killer       string
		Victim       string
		KillWord     KillWord
		AllKillWords AllKillWords
	}
	AllKillWords map[string]KillWords
)

const (
	PlayerJoin EventType = iota + 1
	PlayerLeave
	GameComplete
	AssignmentRotation
)

type Event interface{ event() }

func (EventPlayerJoin) event()         {}
func (EventPlayerLeave) event()        {}
func (EventGameComplete) event()       {}
func (EventAssignmentRotation) event() {}

func EventWithTime(event Event, t time.Time) Event {
	switch e := event.(type) {
	case EventPlayerJoin:
		e.Timestamp = t
		event = e
	case EventPlayerLeave:
		e.Timestamp = t
		event = e
	case EventGameComplete:
		e.Timestamp = t
		event = e
	case EventAssignmentRotation:
		e.Timestamp = t
		event = e
	}
	return event
}

func (games Games) GameEvents(ctx context.Context, id string, since time.Time) ([]Event, error) {
	var results []Event
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		var timestamp time.Time
		var b []byte
		if err := rows.Scan(&timestamp, &b); err != nil {
			return err
		}
		event, err := parseEvent(b, timestamp)
		results = append(results, event)
		return err
	}, `
		SELECT
			timestamp,
			payload
		FROM events
		WHERE game_uuid=? and timestamp>?
		ORDER BY timestamp ASC
	`, id, since)
	return results, err
}

func parseEvent(b []byte, timestamp time.Time) (Event, error) {
	var peek struct {
		Type EventType
	}
	if err := json.Unmarshal(b, &peek); err != nil {
		return nil, err
	}
	switch peek.Type {
	case PlayerJoin:
		var v EventPlayerJoin
		err := json.Unmarshal(b, &v)
		return EventWithTime(v, timestamp), err
	case PlayerLeave:
		var v EventPlayerLeave
		err := json.Unmarshal(b, &v)
		return EventWithTime(v, timestamp), err
	case GameComplete:
		var v EventGameComplete
		err := json.Unmarshal(b, &v)
		return EventWithTime(v, timestamp), err
	case AssignmentRotation:
		var v EventAssignmentRotation
		err := json.Unmarshal(b, &v)
		return EventWithTime(v, timestamp), err
	}
	return nil, fmt.Errorf("unknown event type %d: %s", peek.Type, b)
}

func (games Games) GameState(ctx context.Context, id string) (GameState, error) {
	result := GameState{Players: map[string]PlayerState{}}

	events, err := games.GameEvents(ctx, id, time.Time{})
	if err != nil {
		return result, err
	}

	for _, event := range events {
		switch event.(type) {
		case EventPlayerJoin:
			playerJoin := event.(EventPlayerJoin)
			result.Players[playerJoin.ID] = PlayerState{}
		case EventPlayerLeave:
			playerLeave := event.(EventPlayerLeave)
			delete(result.Players, playerLeave.ID)
		case EventGameComplete:
			gameComplete := event.(EventGameComplete)
			result.Completed = gameComplete.Timestamp
		case EventAssignmentRotation:
			result.Started = true
			assignmentRotation := event.(EventAssignmentRotation)

			if killer, ok := result.Players[assignmentRotation.Killer]; !ok {
			} else if _, ok := result.Players[assignmentRotation.Victim]; !ok {
			} else {
				killer.Kills = append(killer.Kills, Kill{
					Timestamp: assignmentRotation.Timestamp,
					Victim:    assignmentRotation.Victim,
					KillWord:  assignmentRotation.KillWord,
				})
				result.Players[assignmentRotation.Killer] = killer
			}

			for k, v := range result.Players {
				v.KillWords = KillWords{}
				result.Players[k] = v
			}

			for k, v := range assignmentRotation.AllKillWords {
				player := result.Players[k]
				player.KillWords = v
				result.Players[k] = player
			}
		default:
			return GameState{}, fmt.Errorf("unknown event type %T", event)
		}
	}

	return result, err
}

func (games Games) CreateGame(ctx context.Context, name string) (string, error) {
	var exists string
	if err := games.db.Query(ctx,
		func(rows *sql.Rows) error {
			return rows.Scan(&exists)
		},
		`
			SELECT uuid
			FROM games
			WHERE name=? AND completed IS NULL
		`, name); err != nil {
		return "", err
	} else if exists != "" {
		return exists, nil
	}

	id := uuid.New().String()
	return id, games.db.Exec(ctx, `
		INSERT INTO games (
			uuid,
			updated,
			name
		) VALUES (?, ?, ?)
	`, id, time.Now(), name)
}

func (games Games) CreateEventPlayerJoin(ctx context.Context, id string, player string) error {
	if _, err := games.UserName(ctx, player); err != nil {
		return err
	}
	if err := games.db.Exec(ctx, `
		INSERT INTO players (
			game_uuid,
			user_uuid
		) VALUES (?, ?);
	`, id, player); err != nil {
		return err
	}
	return games.createEvent(ctx, id, EventPlayerJoin{Type: PlayerJoin, ID: player})
}

func (games Games) CreateEventPlayerLeave(ctx context.Context, id string, player string) error {
	return games.createEvent(ctx, id, EventPlayerLeave{Type: PlayerLeave, ID: player})
}

func (games Games) CreateEventAssignmentRotation(ctx context.Context, id string, killer, victim, word string, points int) error {
	state, err := games.GameState(ctx, id)
	if err != nil {
		return err
	}

	event := EventAssignmentRotation{
		Type:   AssignmentRotation,
		Killer: killer,
		Victim: victim,
		KillWord: KillWord{
			Word:   word,
			Points: points,
		},
	}

	prevAllKillWords := make(AllKillWords)
	for k, v := range state.Players {
		prevAllKillWords[k] = v.KillWords
	}

	event.AllKillWords = prevAllKillWords.ShuffleAssignees(killer, victim, word)
	event.AllKillWords = event.AllKillWords.FillKillWords()

	return games.createEvent(ctx, id, event)
}

func (words KillWords) Empty() bool {
	return words.Global == (KillWord{}) && words.Assigned.IsZero() && words.Assignee == "" && words.Assignment.Empty()
}

func (words KillWords) Privates() []KillWord {
	a := slices.Clone(words.Assignment.Private)
	slices.SortFunc(a, func(a, b KillWord) int {
		return strings.Compare(a.Word, b.Word)
	})
	return a
}

func (words KillWords) Publics() []KillWord {
	a := slices.Clone(words.Assignment.Public)
	slices.SortFunc(a, func(a, b KillWord) int {
		return strings.Compare(a.Word, b.Word)
	})
	return a
}

func (prev AllKillWords) ShuffleAssignees(killer, victim, word string) AllKillWords {
	m := prev.withoutAssignees()

	if _, ok := prev[killer]; !ok {
	} else if victimState, ok := prev[victim]; !ok {
	} else if killer != victimState.Assignee { // if victim was targeting killer, just randomize
		m.assign(killer, victimState.Assignee)
	}

	for !func() bool {
		allKillWords := maps.Clone(m)
		unassigned := allKillWords.unassigned()
		pop := func() string {
			result := unassigned[0]
			unassigned = unassigned[1:]
			return result
		}

		for k, v := range allKillWords {
			if v.Assignee != "" {
				continue
			}
			v.Assignee = pop()
			if k == v.Assignee || prev[k].Assignee == v.Assignee {
				return false
			}
			allKillWords[k] = v
		}

		if len(unassigned) > 0 {
			panic(unassigned)
		}

		m = allKillWords
		return true
	}() {
	}

	return m
}

func (m AllKillWords) assign(killer, victim string) {
	v := m[killer]
	v.Assignee = victim
	m[killer] = v
}

func (m AllKillWords) withoutAssignees() AllKillWords {
	now := time.Now()
	result := make(AllKillWords)
	for k := range m {
		result[k] = KillWords{
			Global:     m[k].Global,
			Assigned:   now,
			Assignee:   "",
			Assignment: m[k].Assignment,
		}
	}
	return result
}

func (m AllKillWords) unassigned() []string {
	var result []string
	for k := range m {
		if !slices.Contains(m.assigned(), k) {
			result = append(result, k)
		}
	}
	for i := range result {
		j := rand.Intn(i + 1)
		result[i], result[j] = result[j], result[i]
	}
	return result
}

func (m AllKillWords) assigned() []string {
	var result []string
	for k := range m {
		v := m[k].Assignee
		if v == "" {
			continue
		}
		result = append(result, v)
	}
	return result
}

//go:embed holiday.txt
var wordsHoliday string

func (m AllKillWords) FillKillWords() AllKillWords {
	return m.fillKillWords(
		strings.Fields(wordsHoliday),
		1,
		strings.Fields(wordsHoliday), // TODO medium difficulty
		2,
		strings.Fields(wordsHoliday), // TODO hard difficulty
	)
}

func (m AllKillWords) fillKillWords(
	poolGlobal []string,
	nPublic int,
	poolPublic []string,
	nPrivate int,
	poolPrivate []string,
) AllKillWords {
	result := maps.Clone(m)
	m = result
	for k, v := range m {
		if v.Global.Word == "" {
			v.Global = KillWord{Word: m.unusedGlobal(poolGlobal), Points: -1}
			m[k] = v
		}
		if len(v.Assignment.Public) == 0 {
			v.Assignment.Public = []KillWord{}
			for i := 0; i < nPublic; i++ {
				v.Assignment.Public = append(v.Assignment.Public, KillWord{Word: m.unusedPublic(poolPublic), Points: 50})
				m[k] = v
			}
		}
		if len(v.Assignment.Private) == 0 {
			v.Assignment.Private = []KillWord{}
			for i := 0; i < nPrivate; i++ {
				v.Assignment.Private = append(v.Assignment.Private, KillWord{Word: m.unusedPrivate(poolPrivate), Points: 100})
				m[k] = v
			}
		}
	}
	return m
}

func (m AllKillWords) unusedGlobal(pool []string) string {
	inUse := func() []string {
		result := []string{}
		for _, killWords := range m {
			result = append(result, killWords.Global.Word)
		}
		return result
	}
	for {
		picked := pool[rand.Intn(len(pool))]
		if !slices.Contains(inUse(), picked) {
			return picked
		}
	}
}

func (m AllKillWords) unusedPrivate(pool []string) string {
	inUse := func() []string {
		result := []string{}
		for _, killWords := range m {
			for _, killWord := range killWords.Assignment.Private {
				result = append(result, killWord.Word)
			}
		}
		return result
	}
	for {
		picked := pool[rand.Intn(len(pool))]
		if !slices.Contains(inUse(), picked) {
			return picked
		}
	}
}

func (m AllKillWords) unusedPublic(pool []string) string {
	inUse := func() []string {
		result := []string{}
		for _, killWords := range m {
			for _, killWord := range killWords.Assignment.Public {
				result = append(result, killWord.Word)
			}
		}
		return result
	}
	for {
		picked := pool[rand.Intn(len(pool))]
		if !slices.Contains(inUse(), picked) {
			return picked
		}
	}
}

func (games Games) CreateEventGameComplete(ctx context.Context, id string) error {
	if err := games.db.Exec(ctx, `
		UPDATE games
		SET completed=?, updated=?
		WHERE uuid=?
	`, time.Now(), time.Now(), id); err != nil {
		return err
	}
	return games.createEvent(ctx, id, EventGameComplete{Type: GameComplete})
}

func (games Games) createEvent(ctx context.Context, id string, v any) error {
	payload, err := json.Marshal(v)
	if err != nil {
		panic(err)
	}

	return games.db.Exec(ctx, `
		INSERT INTO events (
			game_uuid,
			timestamp,
			payload
		) VALUES (?, ?, ?)
	`, id, time.Now(), payload)
}