package main

import (
	"errors"
	"fmt"
	"log"
	"math"
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

func getEnter(c *gin.Context) {
	tm.Render(c, "enter", gin.H{})
}

func postEnter(c *gin.Context) {
	current := getSessionUser(c)
	if current == nil {
		c.Redirect(http.StatusFound, "/login")
		return
	}

	// Parse form
	a1h := strings.TrimSpace(c.PostForm("a1"))
	a2h := strings.TrimSpace(c.PostForm("a2"))
	b1h := strings.TrimSpace(c.PostForm("b1"))
	b2h := strings.TrimSpace(c.PostForm("b2"))
	scoreA := atoiSafe(c.PostForm("scoreA"))
	scoreB := atoiSafe(c.PostForm("scoreB"))

	// Require a winner
	if scoreA == scoreB {
		SaveForm(c)
		SetMessage(c, "There must be a winner")
		c.Redirect(http.StatusSeeOther, "/enter")
		return
	}

	// Resolve players
	resolveUser := func(handle string) (*User, error) {
		if handle == "" {
			return nil, nil
		}
		u, err := findUserByHandle(handle)
		if err != nil {
			SaveForm(c)
			SetMessage(c, fmt.Sprintf(`Player "%v" does not exist`, handle))
			c.Redirect(http.StatusSeeOther, "/enter")
			return nil, err
		}
		return u, nil
	}

	var a1, a2, b1, b2 *User

	// Always ensure A1 exists, fallback to current if empty
	var err error
	if a1, err = resolveUser(a1h); err != nil {
		return
	}
	if a2, err = resolveUser(a2h); err != nil {
		return
	}
	if b1, err = resolveUser(b1h); err != nil {
		return
	}
	if b2, err = resolveUser(b2h); err != nil {
		return
	}

	// Check for at least one player on each side
	if b1 == nil && b2 == nil || a1 == nil && a2 == nil {
		SaveForm(c)
		SetMessage(c, "There must be at least one player on each side")
		c.Redirect(http.StatusSeeOther, "/enter")
		return
	}

	// Check for duplicate users
	seen := map[uint]bool{}
	users := []*User{a1, a2, b1, b2}
	for i, u := range users {
		if u != nil {
			if seen[u.ID] {
				SaveForm(c)
				SetMessage(c, fmt.Sprintf(`Player "%v" cannot play twice in one game`, users[i].Username))
				c.Redirect(http.StatusSeeOther, "/enter")
				return
			}
			seen[u.ID] = true
		}
	}

	// Create game
	g := Game{
		ScoreA: scoreA,
		ScoreB: scoreB,
	}
	if err := db.Create(&g).Error; err != nil {
		c.String(http.StatusInternalServerError, "game create error")
		return
	}

	var players []Player
	var playerbuf []float64
	for i, user := range users {
		if user != nil {
			var side string
			if i > 1 {
				side = "B"
			} else {
				side = "A"
			}
			players = append(players, Player{u: user, side: side, dElo: 0})
			playerbuf = append(playerbuf, user.Elo)
		}

	}

	team1 := NewTeam(players[:len(players)/2], g.ScoreA)
	team2 := NewTeam(players[len(players)/2:], g.ScoreB)

	// Set new elo for all players
	GetNewElo([]*Team{team1, team2})

	var winningSide string
	if g.ScoreA > g.ScoreB {
		winningSide = "A"
	} else {
		winningSide = "B"
	}

	for i, p := range players {
		db.Save(p.u)
		p.dElo = players[i].u.Elo - playerbuf[i]

		var updateString string
		if p.side == winningSide {
			updateString = "win_count"
		} else {
			updateString = "loss_count"

		}
		var expr = gorm.Expr(updateString+" + ?", 1)

		// Update win or loss
		err = db.Model(&User{}).
			Where("id = ?", p.u.ID).
			UpdateColumn(updateString, expr).UpdateColumn("game_count", gorm.Expr("game_count + ?", 1)).Error
		if err != nil {
			fmt.Println(err)
		}

		if err := db.Create(&GameUser{GameID: g.ID, UserID: p.u.ID, Side: p.side, DeltaElo: p.dElo}).Error; err != nil {
			c.String(http.StatusInternalServerError, "failed to assign player")
			return
		}
	}

	c.Redirect(http.StatusFound, "/history")
}

func getIndex(c *gin.Context) {
	if u := getSessionUser(c); u != nil {
		c.Redirect(302, "/enter")
		return
	}
	getLogin(c)
}

func roundFloat(val float64, precision uint) float64 {
	ratio := math.Pow(10, float64(precision))
	return math.Round(val*ratio) / ratio
}

func getHistory(c *gin.Context) {
	// Load recent games
	var games []Game
	db.Order("created_at desc").Find(&games)

	type UserElo struct {
		User
		DeltaElo float64
	}

	type GRow struct {
		Game
		PlayersA  []UserElo
		PlayersB  []UserElo
		WinnerIsA bool
	}
	var rows []GRow
	for _, g := range games {
		var gps []GameUser
		db.Model(&GameUser{}).Preload("User").Where("game_id = ?", g.ID).Find(&gps)
		var a, b []UserElo
		for _, gp := range gps {
			if gp.Side == "A" {
				a = append(a, UserElo{gp.User, roundFloat(gp.DeltaElo, 2)})
			} else {
				b = append(b, UserElo{gp.User, roundFloat(gp.DeltaElo, 2)})
			}
		}
		rows = append(rows, GRow{Game: g, PlayersA: a, PlayersB: b, WinnerIsA: g.ScoreA > g.ScoreB})

		log.Printf("%+v", rows[0].PlayersA[0].Username)
	}
	tm.Render(c, "history", gin.H{"Games": rows})
}

func getLeaderboard(c *gin.Context) {
	var users []User
	if err := db.Order("elo DESC").Find(&users).Error; err != nil {
		c.String(http.StatusInternalServerError, "Error: %v", err)
		return
	}

	tm.Render(c, "leaderboard", gin.H{
		"Users": users,
	})
}

func getUserView(c *gin.Context) {
	slug := c.Param("userSlug")
	u, err := userBySlug(slug)
	if err != nil {
		c.String(404, "user not found")
		return
	}

	// Check if own user
	var own bool
	if slug == u.Slug {
		own = true
	}

	tm.Render(c, "user", gin.H{"User": u, "Own": own})
}

func getMe(c *gin.Context) {
	u := getSessionUser(c)
	tm.Render(c, "user", gin.H{"User": u, "Own": true})
}

func postMe(c *gin.Context) {
	cu := getSessionUser(c)
	if cu == nil {
		c.Redirect(302, "/login")
		return
	}
	newU := strings.TrimSpace(c.PostForm("username"))
	if newU == "" || newU == cu.Username {
		c.Redirect(302, "/me")
		return
	}

	// Update username and slug
	cu.Username = newU
	cu.Slug = slugify(newU)
	if err := ensureUniqueUsernameAndSlug(cu); err != nil {
		log.Println("unique username error:", err)
	}
	if err := db.Save(cu).Error; err != nil {
		log.Println("save user:", err)
	}
	c.Redirect(302, "/me")
}

func getLogin(c *gin.Context) {
	tm.Render(c, "login", gin.H{})
}

func postLogin(c *gin.Context) {
	email := strings.ToLower(strings.TrimSpace(c.PostForm("email")))
	if email == "" {
		c.Redirect(302, "/login")
		return
	}

	// ensure user exists
	var u User
	tx := db.Where("email = ?", email).First(&u)
	if errors.Is(tx.Error, gorm.ErrRecordNotFound) {
		u = User{Email: email, Username: defaultUsername()}
		if err := ensureUniqueUsernameAndSlug(&u); err != nil {
			log.Println(err)
		}
		if err := db.Create(&u).Error; err != nil {
			log.Println("create user:", err)
		}
	}

	// create token valid 30 days
	token := mustRandToken(24)
	lt := LoginToken{Token: token, Email: email, ExpiresAt: now().Add(30 * 24 * time.Hour)}
	if err := db.Create(&lt).Error; err != nil {
		log.Println("create token:", err)
	}

	link := strings.TrimRight(baseURL, "/") + "/magic?token=" + token
	log.Printf("[MAGIC LINK] %s for %s (valid until %s)\n", link, email, lt.ExpiresAt.Format(time.RFC3339))

	tm.Render(c, "sent", gin.H{"Email": email})
}

func getMagic(c *gin.Context) {
	token := c.Query("token")
	if token == "" {
		c.Redirect(302, "/login")
		return
	}
	var lt LoginToken
	if err := db.Where("token = ? AND expires_at > ?", token, now()).First(&lt).Error; err != nil {
		c.String(400, "Invalid or expired token")
		return
	}
	// find or create user by email again (in case)
	u, err := userByEmail(lt.Email)
	if err != nil {
		c.String(500, "user lookup error")
		return
	}

	// create session
	sessTok := mustRandToken(24)
	if err := db.Create(&Session{Token: sessTok, UserID: u.ID}).Error; err != nil {
		c.String(500, "session error")
		return
	}
	setSessionCookie(c, sessTok)

	c.Redirect(302, "/enter")
}