const std = @import("std");

// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *std.Build) !void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard optimization options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
    // set a preferred release mode, allowing the user to decide how to optimize.
    const optimize = b.standardOptimizeOption(.{});

    // We will also create a module for our other entry point, 'main.zig'.
    const exe_mod = b.createModule(.{
        // `root_source_file` is the Zig "entry point" of the module. If a module
        // only contains e.g. external object files, you can make this `null`.
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });

    // This creates another `std.Build.Step.Compile`, but this one builds an executable
    // rather than a static library.
    const exe = b.addExecutable(.{
        .name = "interpreter",
        .root_module = exe_mod,
    });

    // This declares intent for the executable to be installed into the
    // standard location when the user invokes the "install" step (the default
    // step when running `zig build`).
    b.installArtifact(exe);

    // This is needed for better lsp errors
    const exe_check = b.addExecutable(.{
        .name = "interpreter-lsp",
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });

    const check = b.step("check", "Check if foo compiles");
    check.dependOn(&exe_check.step);

    // This *creates* a Run step in the build graph, to be executed when another
    // step is evaluated that depends on it. The next line below will establish
    // such a dependency.
    const run_cmd = b.addRunArtifact(exe);

    // By making the run step depend on the install step, it will be run from the
    // installation directory rather than directly from within the cache directory.
    // This is not necessary, however, if the application depends on other installed
    // files, this ensures they will be present and in the expected location.
    run_cmd.step.dependOn(b.getInstallStep());

    // This allows the user to pass arguments to the application in the build
    // command itself, like this: `zig build run -- arg1 arg2 etc`
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    // This creates a build step. It will be visible in the `zig build --help` menu,
    // and can be selected like this: `zig build run`
    // This will evaluate the `run` step rather than the default, which is "install".
    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);

    const exe_unit_tests = b.addTest(.{
        .root_module = exe_mod,
    });

    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);

    // Similar to creating the run step earlier, this exposes a `test` step to
    // the `zig build --help` menu, providing a way for the user to request
    // running the unit tests.
    const test_step = b.step("test", "Run unit tests");
    test_step.dependOn(&run_exe_unit_tests.step);

    // Example step - used for testing againt all the example programs
    const examples_step = b.step("examples", "Run examples");
    examples_step.dependOn(&exe.step);

    const examples_dir = "examples";
    var dir = std.fs.cwd().openDir(examples_dir, .{ .iterate = true }) catch |err| {
        std.debug.print("Failed to open examples directory: {}\n", .{err});
        return;
    };
    defer dir.close();

    var iter = dir.iterate();
    while (try iter.next()) |entry| {
        if (entry.kind == .file) {
            const example_path = b.fmt("{s}/{s}", .{ examples_dir, entry.name });
            const run_example = b.addSystemCommand(&.{ "zig", "build", "run", "--", example_path });
            run_example.setName(b.fmt("{s}", .{example_path}));
            run_example.expectExitCode(0);
            examples_step.dependOn(&run_example.step);
        }
    }
}