package game

import (
	"errors"

	"git.sunturtle.xyz/studio/shotgun/player"
	"git.sunturtle.xyz/studio/shotgun/serve"
)

type Game struct {
	RNG    RNG
	PP     [2]Player
	Shells []bool
	Round  uint
	Group  uint
	Turn   uint
	HP     int8
	Damage int8
	Reveal bool
	Prev   *bool

	// Backing storage for shells.
	ShellArray [8]bool
}

// NewGame creates a new game started at round 1.
func NewGame() *Game {
	g := &Game{
		RNG: NewRNG(),
	}
	g.StartRound()
	return g
}

// StartRound starts the next round of a game.
func (g *Game) StartRound() {
	g.HP = int8(g.RNG.Intn(3) + 2)
	g.PP[0].StartRound(g.HP)
	g.PP[1].StartRound(g.HP)
	g.Round++
	g.Group = 0
	g.StartGroup()
}

// StartGroup starts the next shell group of a round.
func (g *Game) StartGroup() {
	items := g.RNG.Intn(4) + 1
	g.PP[0].StartGroup(&g.RNG, items)
	g.PP[1].StartGroup(&g.RNG, items)
	shells := g.RNG.Intn(6) + 2
	for i := 0; i < shells/2; i++ {
		g.ShellArray[i] = true
	}
	for i := shells / 2; i < shells; i++ {
		g.ShellArray[i] = false
	}
	g.Shells = g.ShellArray[:shells]
	ShuffleSlice(&g.RNG, g.Shells)
	g.Group++
	g.Turn = 0
	g.Prev = nil
	g.NextTurn()
}

// NextTurn advances the turn.
func (g *Game) NextTurn() {
	g.Turn++
	g.Damage = 1
	g.Reveal = false
	cur := g.CurrentPlayer()
	skip := cur.Cuffs == CuffedSkip
	cur.Cuffs = cur.Cuffs.NextState()
	if skip {
		g.NextTurn()
	}
}

// CurrentPlayer gets the index of the current player, either 0 or 1.
func (g *Game) CurrentPlayer() *Player {
	return &g.PP[g.Turn%2]
}

// Opponent returns the player who is not the current player.
func (g *Game) Opponent() *Player {
	return &g.PP[g.Turn%2^1]
}

// Apply uses an item by index for the current player.
// This may cause the group to end.
// Returns ErrWrongTurn if id does not correspond to the current player.
func (g *Game) Apply(id player.ID, item int) error {
	cur := g.CurrentPlayer()
	if cur.ID != id {
		return ErrWrongTurn
	}
	if item < 0 || item >= len(cur.Items) {
		return errors.New("item index out of bounds")
	}
	if cur.Items[item].Apply(g) {
		cur.Items[item] = ItemNone
	}
	return nil
}

// PopShell removes a shell from the shotgun.
// This may cause the shotgun to be empty, but does not start the next group
// if so.
func (g *Game) PopShell() bool {
	g.Prev = &g.Shells[0]
	g.Shells = g.Shells[1:]
	return *g.Prev
}

// Peek returns the current turn's shell if it is revealed for the player with
// the given ID, or nil otherwise.
func (g *Game) Peek(id player.ID) *bool {
	if len(g.Shells) == 0 || id != g.CurrentPlayer().ID || !g.Reveal {
		return nil
	}
	return &g.Shells[0]
}

// Empty returns whether the shotgun is empty.
func (g *Game) Empty() bool {
	return len(g.Shells) == 0
}

// Winner returns the player who won, or nil if the round is not over.
func (g *Game) Winner() *Player {
	if g.PP[0].HP <= 0 {
		return &g.PP[1]
	}
	if g.PP[1].HP <= 0 {
		return &g.PP[0]
	}
	return nil
}

// Shoot fires the shotgun, at the opponent if self is false and at the current
// player if self is true. Afterward, the round may be over, or the shotgun may
// be empty.
// Returns ErrWrongTurn if id does not correspond to the current player.
func (g *Game) Shoot(id player.ID, self bool) error {
	cur := g.CurrentPlayer()
	if cur.ID != id {
		return ErrWrongTurn
	}
	target := g.Opponent()
	if self {
		target = g.CurrentPlayer()
	}
	live := g.PopShell()
	if live {
		target.HP -= g.Damage
		g.NextTurn()
	} else if !self {
		g.NextTurn()
	}
	return nil
}

// DTO returns the current game state as viewed by the given player.
func (g *Game) DTO(id player.ID) serve.Game {
	return serve.Game{
		Players: [2]serve.Player{
			g.PP[0].DTO(),
			g.PP[1].DTO(),
		},
		Round:    g.Round,
		Damage:   g.Damage,
		Shell:    g.Peek(id),
		Previous: g.Prev,
	}
}

// ShellCounts returns the number of live and blank shells.
func (g *Game) ShellCounts() serve.ShellCounts {
	var counts serve.ShellCounts
	for _, s := range g.Shells {
		if s {
			counts.Live++
		} else {
			counts.Blank++
		}
	}
	return counts
}

var ErrWrongTurn = errors.New("not your turn")