package main

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"maps"
	"math/rand"
	"slices"
	"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) GameByName(ctx context.Context, uid, name string) (string, error) {
	var result string
	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		return rows.Scan(&result)
	}, `
		SELECT
			players.game_uuid
		FROM
			players
		JOIN games ON players.game_uuid=games.uuid
		WHERE players.user_uuid=? AND games.name=?
		ORDER BY games.updated DESC
		LIMIT 1
	`, uid, name)
	return result, err
}

type (
	GameState struct {
		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 string

		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
		ID   string
	}
	EventPlayerLeave struct {
		Type EventType
		ID   string
	}
	EventGameComplete struct {
		Type EventType
	}
	EventAssignmentRotation struct {
		Type      EventType
		Killer    string
		Victim    string
		KillWord  KillWord
		KillWords map[string]KillWords
	}
)

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

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

	err := games.db.Query(ctx, func(rows *sql.Rows) error {
		var timestamp time.Time
		var payload []byte
		if err := rows.Scan(&timestamp, &payload); err != nil {
			return err
		}

		var peek struct {
			Type EventType
		}
		if err := json.Unmarshal(payload, &peek); err != nil {
			return err
		}

		switch peek.Type {
		case PlayerJoin:
			var playerJoin EventPlayerJoin
			if err := json.Unmarshal(payload, &playerJoin); err != nil {
				return err
			}
			result.Players[playerJoin.ID] = PlayerState{}
			return nil
		case PlayerLeave:
			var playerLeave EventPlayerLeave
			if err := json.Unmarshal(payload, &playerLeave); err != nil {
				return err
			}
			delete(result.Players, playerLeave.ID)
			return nil
		case GameComplete:
			var gameComplete EventGameComplete
			if err := json.Unmarshal(payload, &gameComplete); err != nil {
				return err
			}
			result.Completed = timestamp
			return nil
		case AssignmentRotation:
			var assignmentRotation EventAssignmentRotation
			if err := json.Unmarshal(payload, &assignmentRotation); err != nil {
				return err
			}

			if killer, ok := result.Players[assignmentRotation.Killer]; !ok {
			} else if _, ok := result.Players[assignmentRotation.Victim]; !ok {
			} else {
				killer.Kills = append(killer.Kills, Kill{
					Timestamp: 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.KillWords {
				player := result.Players[k]
				player.KillWords = v
				result.Players[k] = player
			}
			return nil
		default:
			return fmt.Errorf("unknown event type %d: %s", peek.Type, payload)
		}

		return nil
	}, `
		SELECT timestamp, payload
		FROM events
		WHERE game_uuid=?
	`, id)

	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.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
	}
	now := time.Now()

	event := EventAssignmentRotation{
		Type:   AssignmentRotation,
		Killer: killer,
		Victim: victim,
		KillWord: KillWord{
			Word:   word,
			Points: points,
		},
		KillWords: map[string]KillWords{},
	}

	toAssign := []string{}
	doNotAssign := map[string]string{}

	for k, v := range state.Players {
		v := v.KillWords
		toAssign = append(toAssign, k)
		doNotAssign[k] = v.Assignee

		event.KillWords[k] = KillWords{
			Global:     v.Global,
			Assigned:   now,
			Assignee:   "",
			Assignment: v.Assignment,
		}
	}

	if killerState, ok := state.Players[killer]; !ok {
	} else if victimState, ok := state.Players[victim]; !ok {
	} else {
		event.KillWords[killer] = KillWords{
			Global:     killerState.KillWords.Global,
			Assigned:   now,
			Assignee:   victimState.KillWords.Assignee,
			Assignment: killerState.KillWords.Assignment,
		}
		toAssign = slices.DeleteFunc(toAssign, func(s string) bool { return s == event.KillWords[killer].Assignee })
	}

	for !func() bool {
		toAssign := slices.Clone(toAssign)
		doNotAssign := maps.Clone(doNotAssign)
		eventKillWords := maps.Clone(event.KillWords)

		for i := range toAssign {
			j := rand.Intn(i + 1)
			toAssign[i], toAssign[j] = toAssign[j], toAssign[i]
		}
		for k, v := range eventKillWords {
			if k == toAssign[0] || doNotAssign[k] == toAssign[0] {
				return false
			}
			eventKillWords[k] = KillWords{
				Global:     v.Global,
				Assigned:   now,
				Assignee:   toAssign[0],
				Assignment: v.Assignment,
			}
			toAssign = toAssign[1:]
		}

		event.KillWords = eventKillWords
		return true
	}() {
	}

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

func (games Games) CreateEventGameComplete(ctx context.Context, id string) error {
	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)
}