const std = @import("std");
const tree = @import("tree.zig");
const Arena = @import("arena.zig").Arena;
const embed = @import("kernel_embed");

/// Copy the embedded kernel into an arena, returning the new root index.
/// This allows the kernel to be used in App nodes alongside application terms.
pub fn loadKernel(arena: *Arena) !u32 {
    var mapping = try arena.allocator.alloc(u32, embed.kernel_nodes.len);
    defer arena.allocator.free(mapping);

    for (embed.kernel_nodes, 0..) |node, i| {
        const idx: u32 = @intCast(i);
        mapping[idx] = switch (node) {
            .leaf => try arena.alloc(.leaf),
            .stem => |s| try arena.alloc(.{ .stem = .{ .child = mapping[s.child] } }),
            .fork => |f| try arena.alloc(.{ .fork = .{ .left = mapping[f.left], .right = mapping[f.right] } }),
        };
    }

    return mapping[embed.kernel_root];
}