// The alliance / shared-vision mask -- the spine's fourth phase.
//
// Early in every strategic turn, before anything else in the turn can read it, the driver
// walks the server's player vector and rebuilds one word on each player's turn record from
// scratch. The word is a bitmask of "whose vision this player shares this turn": the player's
// own bit, plus every member of the player's alliance when it is in one.
//
// Two things about it are worth stating in the header because both are places a
// reimplementation goes quietly wrong.
//
//  1. The bit is the player's POSITION IN THE PLAYER VECTOR, not the player's own index
//     field. Every other per-player index in the tail -- the turn-results array, the battle
//     tally, the archive key -- uses the index field, and this one does not. The shift count
//     in the original is the loop induction variable; the index field is never loaded in this
//     phase.
//  2. The mask is rebuilt, not accumulated. The word is cleared first, so nothing survives
//     from the previous turn.
//
// The word is not itself a save leaf. It reaches the wire only because the last phase of the
// post-combat tail copies the whole turn record into the per-turn statistics archive, which
// IS on the wire -- so this phase is checkable against bytes the original wrote.
#pragma once

#include <cstddef>
#include <cstdint>
#include <vector>

#include "mars/stream/shapes.h"

namespace sots::app {

// The value the original uses for "this player is in no alliance".
constexpr std::int32_t kNoAlliance = -1;

// One player's mask. `vectorIndex` is the player's position in the server's player vector.
//
// Above 31 players the original's shift wraps -- x86 masks a variable shift count to five
// bits -- so bit (index % 32) would be set. No save in the corpus has more than eight
// players and that path is untested; it is reproduced rather than "fixed" because the point
// of this file is to be the original, not to be correct.
std::int32_t AllianceMask(const mars::stream::shapes::Player& p, std::size_t vectorIndex);

// The whole phase: every player's mask, in vector order.
std::vector<std::int32_t> RebuildAllianceMasks(
    const std::vector<mars::stream::shapes::PlayerEntry>& players);

}  // namespace sots::app