CardSimEngine/cardsim/player.go

package cardsim

import "math/rand"

// Player stores all gameplay state for one player at a specific point in time.
// Game-specific data is stored in Stats.
//
// Player is a generic type -- see https://go.dev/blog/intro-generics for more
// information on how these work. Think of "Player" as a "type of type" --
// when you create one, you tell it what kind of data it needs to keep for
// the simulation itself, and each Player that works with a different kind of
// data is a different kind of Player and the compiler will help you with that.
// This is the same idea as "slice of something" or "map from something to
// something" -- different kinds of Players are different from each other and
// "know" what type of data they use, so the compiler can tell you if you're
// using the wrong type.
//
// Generic types have to use a placeholder to represent the type (or types --
// consider maps, which have both keys and values) that will be more specific
// when the type is actually used. They're called "type parameters", like
// function parameters, because they're the same kind of idea. A function puts
// its parameters into variables so you can write a function that works with
// whatever data it gets; a generic type takes type parameters and represents
// them with type placeholders so you can write a *type* that works with
// whatever specific other types it gets.
//
// Just like function parameters have a type that says what kind of data the
// function works with, type parameters have a "type constraint" that says what
// kind of types the generic type works with. Go already has a familiar way
// to express the idea of "what a type has to do": `interface`. In Go, type
// constraints are just interfaces.
//
// But wait, why use generics at all? Can't we just use an interface in the
// normal way instead of doing this thing? Well, yes, we could, but then the
// compiler doesn't know that the "real types" for things matching these
// interfaces all have to actually be the same type. The compiler will stop
// you from putting an `Orange` into a `[]Apple`, but it wouldn't stop you from
// putting a `Fruit` into a `[]Fruit` because, well, of course it wouldn't,
// they're the same type.
//
// Different simulation games made with `cardsim` are different. Rules made for
// simulating the economy of a kobold colony and mine wouldn't work at all with
// data for a simulation about three flocks of otter-gryphons having a
// territory conflict over a river full of fish. By using generics, the compiler
// can recognize functions and data and types intended for different simulation
// games and prevent you from using the wrong one, when it wouldn't be able to
// if all this stuff was written for "some simulation game, don't care what".
//
// Generic interfaces (like `Card[C]`, `Rule[C]`, `InfoPanel[C]`, and more)
// don't mean you have to write generics of your own. It's exactly the opposite!
// Because the interface has this extra type in it, you only need to implement
// the specific kind of interface that works with your game. There's more detail
// on this in the comment on `Rule[C]`.
type Player[C StatsCollection] struct {
	// Stats stores simulation-specific state.
	Stats C

	// Name stores the player's name.
	Name string

	// Rand is a source of randomness that other components can use.
	Rand rand.Rand

	Deck       *Deck[C]
	Hand       []Card[C]
	TurnNumber int
	State      GameState

	// HandLimit is number of cards to draw to at the start of each turn.
	// If the player has more cards than this already, none will be drawn,
	// but the player will keep them all.
	//
	// If this is 0 or less and the player has no cards in hand, no permanent
	// actions available, and must take an action, the game ends in stalemate.
	HandLimit int

	// ActionsPerTurn is what ActionsRemaining resets to at the start of each
	// turn. If this is 0 or less at the start of a turn, the game ends in
	// stalemate. Activating a card or permanent action spends an action, but
	// the card or action itself can counter this by changing the player's
	// ActionsRemaining by giving the action back -- or force the turn to
	// progress immediately to simulation by setting it to 0.
	ActionsPerTurn   int
	ActionsRemaining int

	// PermanentActions are an "extra hand" of cards that are not discarded when used.
	PermanentActions []Card[C]

	// InfoPanels lists informational views available to the player. The Prompt
	// is the InfoPanel shown before the main action menu.
	InfoPanels []InfoPanel[C]
	Prompt     InfoPanel[C]

	// Rules are the simulation rules executed every turn after the player has
	// run out of remaining actions. See `RuleCollection`'s documentation for
	// more information about how rule execution works.
	Rules *RuleCollection[C]

	// Temporary messages are shown *before* the Prompt. They're cleared just
	// before executing rules for the turn, so rules adding to TemporaryMessages
	// are creating messages that will show up for the next turn. Temporary
	// panels are cleared out at the same time as temporary messages; when
	// available, they are listed separately from standard panels (before them).
	TemporaryMessages []Message
	TemporaryPanels   []InfoPanel[C]

	// DebugLevel stores how verbose the game should be about errors. If this
	// is greater than 0, invisible stats will usually be shown to the player
	// (this is up to individual info panels, though). If this is -1 or lower,
	// warning messages will not be displayed.
	DebugLevel int
}

// GameState represents various states a player's Game can be in.
type GameState int

const (
	// The game has not started.
	GameUninitialized = GameState(iota)

	// The game is ready to play.
	GameActive

	// The game is over and the player has lost.
	GameLost

	// The game is over and the player has won.
	GameWon

	// The game is over because of an error.
	GameCrashed

	// The game is over because the player cannot take any actions.
	GameStalled
)

// Over returns whether this state represents a game that is over.
func (g GameState) Over() bool {
	return g == GameLost || g == GameWon || g == GameCrashed || g == GameStalled
}