// SPDX-FileCopyrightText: © 2026 Jeffrey C. Ollie <jeff@ocjtech.us>
// SPDX-License-Identifier: MIT

const std = @import("std");

/// The book the tests read: a Project Gutenberg edition of *On the Origin of
/// Species*. It is fetched during `zig build test` rather than committed, since
/// it is several hundred kilobytes of binary that never changes with the code.
///
/// Gutenberg regenerates these files from time to time, so this hash will
/// eventually stop matching. When that happens, check the new file over and
/// update the hash — the tests are written to survive the book changing.
const testdata_url = "https://www.gutenberg.org/cache/epub/2009/pg2009-images.mobi";
const testdata_sha256 = "44a8f228aa0f0f9ceae098885bbf1cc2db6ee79c22c3e4993f86a16daf6cafe7";

/// Download the test book and hand back the path it landed in. The build graph
/// only reaches this when something depends on it, so a plain `zig build` stays
/// offline, and the result is cached between runs.
fn testDataPath(b: *std.Build, tls_module: *std.Build.Module) std.Build.LazyPath {
    const fetch = b.addExecutable(.{
        .name = "fetch",
        .root_module = b.createModule(.{
            .root_source_file = b.path("tools/fetch.zig"),
            // A build-time tool, so it always targets the machine doing the
            // building rather than whatever the library is cross-compiled for.
            .target = b.graph.host,
            .optimize = .ReleaseSafe,
            .imports = &.{
                .{ .name = "tls", .module = tls_module },
            },
        }),
    });

    const run = b.addRunArtifact(fetch);
    run.addArg(testdata_url);
    run.addArg(testdata_sha256);
    return run.addOutputFileArg("CharlesDarwin.mobi");
}

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});
    const mod = b.addModule("mobi", .{
        .root_source_file = b.path("src/root.zig"),
        .target = target,
        .optimize = optimize,
    });

    const exe = b.addExecutable(.{
        .name = "mobi",
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/main.zig"),
            .target = target,
            .optimize = optimize,
            .imports = &.{
                .{ .name = "mobi", .module = mod },
            },
        }),
    });

    b.installArtifact(exe);

    const run_step = b.step("run", "Run the app");

    const run_cmd = b.addRunArtifact(exe);
    run_step.dependOn(&run_cmd.step);

    run_cmd.step.dependOn(b.getInstallStep());

    run_cmd.addPassthruArgs();

    // A separate module for the tests, so that the fetched book is visible to
    // `@embedFile` there without becoming part of the published module and
    // dragging the download into every dependent's build.
    const test_mod = b.createModule(.{
        .root_source_file = b.path("src/root.zig"),
        .target = target,
        .optimize = optimize,
    });
    const tls_module = b.dependency("tls", .{}).module("tls");
    test_mod.addAnonymousImport("testdata", .{ .root_source_file = testDataPath(b, tls_module) });

    const mod_tests = b.addTest(.{
        .root_module = test_mod,
    });

    const run_mod_tests = b.addRunArtifact(mod_tests);

    const exe_tests = b.addTest(.{
        .root_module = exe.root_module,
    });

    const run_exe_tests = b.addRunArtifact(exe_tests);

    const test_step = b.step("test", "Run tests");
    test_step.dependOn(&run_mod_tests.step);
    test_step.dependOn(&run_exe_tests.step);
}