package ai

import (
	"fmt"
	"math/rand/v2"

	"github.com/greyson/super-auto-pets-board-game/internal/game"
)

// ctx is per-decision scratch state: the view, the memory, and caches shared
// by every candidate evaluated in the same decision.
type ctx struct {
	v       *game.View
	m       *Memory
	me      *game.PlayerView
	oppSeat int
	pools   map[int][]game.Card // unseen cards per tier, for hidden-card guesses
	simID   int
}

func newCtx(v *game.View, m *Memory) *ctx {
	cx := &ctx{v: v, m: m, me: &v.Players[v.YouSeat], oppSeat: m.Opp.Seat, pools: map[int][]game.Card{}}
	if cx.oppSeat == cx.me.Seat || cx.oppSeat < 0 {
		// Memory hasn't observed yet (shouldn't happen in practice).
		for _, p := range v.Players {
			if p.Seat != v.YouSeat {
				cx.oppSeat = p.Seat
			}
		}
	}
	return cx
}

func (cx *ctx) nextSimID() string {
	cx.simID++
	return fmt.Sprintf("sim-%d", cx.simID)
}

// unseenPool lists the printed cards of a tier that the bot cannot account
// for anywhere it can see — its own deck, the opponent model, the shop row.
// Hidden opponent cards are drawn from this pool, so the bot's guesses
// respect card counting without peeking at the real decks.
func (cx *ctx) unseenPool(tier int) []game.Card {
	if pool, ok := cx.pools[tier]; ok {
		return pool
	}
	seen := map[string]int{}
	note := func(c game.Card) {
		if c.Tier == tier {
			seen[c.Name]++
		}
	}
	for _, c := range cx.me.Deck {
		note(c)
	}
	for _, c := range cx.m.Opp.Known {
		note(c)
	}
	for _, c := range cx.v.ShopRow {
		note(c)
	}
	var pool []game.Card
	for _, c := range game.TierContents(tier) {
		if seen[c.Name] > 0 {
			seen[c.Name]--
			continue
		}
		pool = append(pool, c)
	}
	cx.pools[tier] = pool
	return pool
}

// sampleOppDeck instantiates one concrete guess at the opponent's deck:
// known cards as-is, hidden cards drawn from the unseen pool of their tier
// (or their named template, when a pick was later revealed).
func (cx *ctx) sampleOppDeck() []game.Card {
	deck := append([]game.Card(nil), cx.m.Opp.Known...)
	for _, h := range cx.m.Opp.Hidden {
		var c game.Card
		if t, ok := templateByName(h.Name); ok {
			c = t
		} else if pool := cx.unseenPool(h.Tier); len(pool) > 0 {
			c = pool[rand.IntN(len(pool))]
		} else {
			continue // tier exhausted and fully accounted for; nothing to guess
		}
		c.ID = cx.nextSimID()
		deck = append(deck, c)
	}
	return deck
}

// oppArrangements produces n independent guesses of what the opponent will
// field: each is a sampled deck put in a plausible order by the same
// heuristic the bot itself uses, with enough noise that the bot prepares for
// a range of opponent plans rather than assuming one. The first guess is the
// noise-free "book" ordering.
func (cx *ctx) oppArrangements(n int) [][]game.Card {
	out := make([][]game.Card, 0, n)
	for i := range n {
		temp := 0.8
		if i == 0 {
			temp = 0
		}
		out = append(out, heuristicOrder(cx.sampleOppDeck(), temp))
	}
	return out
}