// SPDX-License-Identifier: LGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// The conditions `crafter-debug wait` and `pause --when` take: comparisons of
// watch paths with literals and with each other, combined with && || ! and
// parentheses.
//
//     fort1.core.hp <= 0
//     scene == "Game" && !debug.paused
//     bodies[3].pos.y < -10 || (lives == 0 && score > highScore)
//
// A lone operand tests truthiness: true, a nonzero number, a non-empty
// string, array or object. Numbers compare by value, strings in byte order;
// == and != work on any two values, and ordering a string against a number
// is an error rather than false, so a typo in a condition is reported
// instead of waiting forever. Parsed once when it arrives, evaluated on the
// Pump thread every frame.
export module Crafter.Debug:Condition;
import std;
import Crafter.Debug.Core;

export namespace Crafter::Debug {
    class ConditionError : public std::runtime_error {
    public:
        std::size_t offset;
        ConditionError(std::size_t offset, std::string_view what);
    };

    class Condition {
    public:
        // Throws ConditionError, with the offset of the problem.
        static Condition Parse(std::string_view text);

        // Looks a path up: a value, or why there is none.
        using Resolver = std::function<std::expected<Value, std::string>(std::string_view path)>;
        // True or false, or why it cannot be decided (an unknown path, or
        // operands that cannot be ordered).
        std::expected<bool, std::string> Evaluate(const Resolver& resolve) const;

        const std::string& Text() const { return text; }
        // The paths the condition reads, in order of appearance.
        std::span<const std::string> Paths() const { return paths; }

        struct Node;

    private:
        std::string text;
        std::shared_ptr<const Node> root;
        std::vector<std::string> paths;
    };
}