sots-engine/src/game/sim/research.cpp

#include "game/sim/research.h"

#include <algorithm>
#include <cmath>
#include <cstddef>
#include <cstdint>

#include "game/sim/numeric.h"

namespace sots::sim {

bool RollEdgeAvailable(const EdgeAvailability& edge, Species species, TreeBuildMode mode,
                       IRandom& rng) {
    if (mode == TreeBuildMode::Everything) return true;
    const float p = edge.Chance(species);
    if (!(p > 0.f)) return false;
    if (mode == TreeBuildMode::NoRoll) return true;
    if (p >= 1.f) return true;
    return rng.NextFloat() <= p;
}

double TechCostMultiplier(int applicableBonusTechsOwned) {
    const double m = 1.0 - 0.25 * std::max(0, applicableBonusTechsOwned);
    return std::max(0.25, m);
}

int TechCost(int baseCost, double multiplier) {
    if (baseCost == kNoResearchCost) return kNoResearchCost;
    return std::max(1, Ftol(static_cast<double>(baseCost) * multiplier));
}

namespace {
// The image's copies of two float literals, widened to double: the per-turn decay
// fraction and the "completed early" threshold. Both are (double)0.05f and (double)0.8f,
// not the exact decimals, and both sit on a truncation/compare boundary where the
// difference is observable.
constexpr double kDecayFraction = 0.05000000074505806;   // (double)0.05f
constexpr double kEarlyCompletionRatio = 0.800000011920929;  // (double)0.8f

// 32-bit signed multiply then truncating division by 100, exactly as the original does it
// (it wraps rather than widening, which only matters for a cost near INT_MAX).
int scale_percent(int cost, unsigned percent) {
    const std::int32_t p = static_cast<std::int32_t>(static_cast<std::uint32_t>(cost) * percent);
    return static_cast<int>(p / 100);
}
}  // namespace

int ResearchSpendFloor(int cost) { return std::max(0, scale_percent(cost, 50u)); }

int ResearchSpendCeiling(int cost) {
    return std::max(ResearchSpendFloor(cost), scale_percent(cost, 150u));
}

float ResearchCompletionOdds(int progress, int lo, int hi) {
    return static_cast<float>(static_cast<double>(progress - lo) / static_cast<double>(hi));
}

ResearchStepResult ApplyResearchPoints(ResearchNode& node, int points, Species owner, IRandom& rng) {
    ResearchStepResult r;
    const int cost = node.cost;
    const int lo = ResearchSpendFloor(cost);
    const int hi = ResearchSpendCeiling(cost);

    r.wasCompleteBefore = cost <= node.progress;
    // Signed min with no floor at zero: the original clamps neither side.
    r.spent = std::min(points, hi - node.progress);
    r.overbudget = points - r.spent;
    node.progress += r.spent;
    const bool nowComplete = cost <= node.progress;

    if (node.progress < hi) {
        if (r.spent == 0) {
            r.odds = 0.f;
            r.roll = 1.f;
        } else {
            r.odds = ResearchCompletionOdds(node.progress, lo, hi);
            r.roll = rng.NextFloat();
            // Zuul draw a second time and keep the lower (better) roll.
            if (owner == Species::Zuul) r.roll = std::min(r.roll, rng.NextFloat());
        }
    } else {
        r.odds = 1.f;
        r.roll = 0.f;
    }

    if (r.odds < r.roll) {
        if (!r.wasCompleteBefore && nowComplete) {
            r.overbudgetEvent = true;
            node.flag = TechFlag::OverBudgetNotified;
        }
        return r;
    }

    r.completed = true;
    // The ratio is itself narrowed to float32 before the comparison.
    const float ratio = static_cast<float>(static_cast<double>(node.progress) / static_cast<double>(cost));
    if (static_cast<double>(ratio) < kEarlyCompletionRatio) {
        r.completedEarly = true;
        node.flag = TechFlag::CompletedEarly;
    }
    node.state = TechState::Researched;
    return r;
}

int DecayResearchProgress(int progress, int cost) {
    return std::max(0, progress - Ftol(static_cast<double>(cost) * kDecayFraction));
}

void DecayAllResearch(std::vector<ResearchNode>& nodes) {
    for (ResearchNode& n : nodes) {
        // The original's guard is `progress != 0`, so a negative progress decays too.
        if (n.state == TechState::Available && n.progress != 0) {
            n.progress = DecayResearchProgress(n.progress, n.cost);
        }
    }
}

ResearchTurnResult ProcessResearchTurn(std::vector<ResearchNode>& nodes,
                                       const std::vector<ResearchAllocEntry>& alloc, Species owner,
                                       IRandom& rng) {
    ResearchTurnResult out;
    out.steps.reserve(alloc.size());
    for (const ResearchAllocEntry& e : alloc) {
        if (e.nodeIndex < 0 || static_cast<std::size_t>(e.nodeIndex) >= nodes.size()) continue;
        ResearchStepResult s = ApplyResearchPoints(nodes[e.nodeIndex], e.points, owner, rng);
        out.overbudget += s.overbudget;
        out.steps.push_back(s);
    }
    DecayAllResearch(nodes);
    return out;
}

bool RollLabAccident(int oddsPercent, IRandom& rng) {
    const int roll = static_cast<int>(rng.NextIntInclusive(100));
    return roll < oddsPercent;
}

int LabAccidentLossPercent(double minLoss, double maxLoss, IRandom& rng) {
    const double f = Clamp01(static_cast<double>(rng.NextFloat()) * (maxLoss - minLoss) + minLoss);
    return static_cast<int>(std::ceil(f * 100.0));
}

}  // namespace sots::sim