const builtin = @import("builtin");
const std = @import("std");
const Builder = std.build.Builder;
const tests = @import("test/tests.zig");
const BufMap = std.BufMap;
const warn = std.debug.warn;
const mem = std.mem;
const ArrayList = std.ArrayList;
const io = std.io;
const fs = std.fs;
const InstallDirectoryOptions = std.build.InstallDirectoryOptions;
const assert = std.debug.assert;

const zig_version = std.builtin.Version{ .major = 0, .minor = 6, .patch = 0 };

pub fn build(b: *Builder) !void {
    b.setPreferredReleaseMode(.ReleaseFast);
    const mode = b.standardReleaseOptions();
    const target = b.standardTargetOptions(.{});

    var docgen_exe = b.addExecutable("docgen", "doc/docgen.zig");

    const rel_zig_exe = try fs.path.relative(b.allocator, b.build_root, b.zig_exe);
    const langref_out_path = fs.path.join(
        b.allocator,
        &[_][]const u8{ b.cache_root, "langref.html" },
    ) catch unreachable;
    var docgen_cmd = docgen_exe.run();
    docgen_cmd.addArgs(&[_][]const u8{
        rel_zig_exe,
        "doc" ++ fs.path.sep_str ++ "langref.html.in",
        langref_out_path,
    });
    docgen_cmd.step.dependOn(&docgen_exe.step);

    const docs_step = b.step("docs", "Build documentation");
    docs_step.dependOn(&docgen_cmd.step);

    const test_step = b.step("test", "Run all the tests");

    var test_stage2 = b.addTest("src/test.zig");
    test_stage2.setBuildMode(mode);
    test_stage2.addPackagePath("stage2_tests", "test/stage2/test.zig");

    const fmt_build_zig = b.addFmt(&[_][]const u8{"build.zig"});

    const skip_release = b.option(bool, "skip-release", "Main test suite skips release builds") orelse false;
    const skip_release_small = b.option(bool, "skip-release-small", "Main test suite skips release-small builds") orelse skip_release;
    const skip_release_fast = b.option(bool, "skip-release-fast", "Main test suite skips release-fast builds") orelse skip_release;
    const skip_release_safe = b.option(bool, "skip-release-safe", "Main test suite skips release-safe builds") orelse skip_release;
    const skip_non_native = b.option(bool, "skip-non-native", "Main test suite skips non-native builds") orelse false;
    const skip_libc = b.option(bool, "skip-libc", "Main test suite skips tests that link libc") orelse false;
    const skip_compile_errors = b.option(bool, "skip-compile-errors", "Main test suite skips compile error tests") orelse false;

    const only_install_lib_files = b.option(bool, "lib-files-only", "Only install library files") orelse false;
    const enable_llvm = b.option(bool, "enable-llvm", "Build self-hosted compiler with LLVM backend enabled") orelse false;
    const config_h_path_option = b.option([]const u8, "config_h", "Path to the generated config.h");

    b.installDirectory(InstallDirectoryOptions{
        .source_dir = "lib",
        .install_dir = .Lib,
        .install_subdir = "zig",
        .exclude_extensions = &[_][]const u8{
            "test.zig",
            "README.md",
            ".z.0",
            ".z.9",
            ".gz",
            "rfc1951.txt",
        },
    });

    if (only_install_lib_files)
        return;

    const tracy = b.option([]const u8, "tracy", "Enable Tracy integration. Supply path to Tracy source");
    const link_libc = b.option(bool, "force-link-libc", "Force self-hosted compiler to link libc") orelse enable_llvm;

    var exe = b.addExecutable("zig", "src/main.zig");
    exe.install();
    exe.setBuildMode(mode);
    exe.setTarget(target);
    test_step.dependOn(&exe.step);
    b.default_step.dependOn(&exe.step);

    exe.addBuildOption(bool, "have_llvm", enable_llvm);
    if (enable_llvm) {
        const config_h_text = if (config_h_path_option) |config_h_path|
            try std.fs.cwd().readFileAlloc(b.allocator, toNativePathSep(b, config_h_path), max_config_h_bytes)
        else
            try findAndReadConfigH(b);

        var ctx = parseConfigH(b, config_h_text);
        ctx.llvm = try findLLVM(b, ctx.llvm_config_exe);

        try configureStage2(b, exe, ctx, tracy != null);
    }
    if (link_libc) {
        exe.linkLibC();
        test_stage2.linkLibC();
    }

    const log_scopes = b.option([]const []const u8, "log", "Which log scopes to enable") orelse &[0][]const u8{};
    const zir_dumps = b.option([]const []const u8, "dump-zir", "Which functions to dump ZIR for before codegen") orelse &[0][]const u8{};

    const opt_version_string = b.option([]const u8, "version-string", "Override Zig version string. Default is to find out with git.");
    const version = if (opt_version_string) |version| version else v: {
        const version_string = b.fmt("{}.{}.{}", .{ zig_version.major, zig_version.minor, zig_version.patch });

        var code: u8 = undefined;
        const git_sha_untrimmed = b.execAllowFail(&[_][]const u8{
            "git",    "-C",          b.build_root,     "name-rev", "HEAD",
            "--tags", "--name-only", "--no-undefined", "--always",
        }, &code, .Ignore) catch {
            break :v version_string;
        };
        const git_sha_trimmed = mem.trim(u8, git_sha_untrimmed, " \n\r");
        // Detect dirty changes.
        const diff_untrimmed = b.execAllowFail(&[_][]const u8{
            "git", "-C", b.build_root, "diff", "HEAD",
        }, &code, .Ignore) catch |err| {
            std.debug.print("Error executing git diff: {}", .{err});
            std.process.exit(1);
        };
        const trimmed_diff = mem.trim(u8, diff_untrimmed, " \n\r");
        const dirty_suffix = if (trimmed_diff.len == 0) "" else s: {
            const dirty_hash = std.hash.Wyhash.hash(0, trimmed_diff);
            break :s b.fmt("dirty{x}", .{@truncate(u32, dirty_hash)});
        };

        // This will look like e.g. "0.6.0^0" for a tag commit.
        if (mem.endsWith(u8, git_sha_trimmed, "^0")) {
            const git_ver_string = git_sha_trimmed[0 .. git_sha_trimmed.len - 2];
            if (!mem.eql(u8, git_ver_string, version_string)) {
                std.debug.print("Expected git tag '{}', found '{}'", .{ version_string, git_ver_string });
                std.process.exit(1);
            }
            break :v b.fmt("{}{}", .{ version_string, dirty_suffix });
        } else {
            break :v b.fmt("{}+{}{}", .{ version_string, git_sha_trimmed, dirty_suffix });
        }
    };
    exe.addBuildOption([]const u8, "version", version);

    exe.addBuildOption([]const []const u8, "log_scopes", log_scopes);
    exe.addBuildOption([]const []const u8, "zir_dumps", zir_dumps);
    exe.addBuildOption(bool, "enable_tracy", tracy != null);
    exe.addBuildOption(bool, "is_stage1", false);
    if (tracy) |tracy_path| {
        const client_cpp = fs.path.join(
            b.allocator,
            &[_][]const u8{ tracy_path, "TracyClient.cpp" },
        ) catch unreachable;
        exe.addIncludeDir(tracy_path);
        exe.addCSourceFile(client_cpp, &[_][]const u8{ "-DTRACY_ENABLE=1", "-fno-sanitize=undefined" });
        if (!enable_llvm) {
            exe.linkSystemLibraryName("c++");
        }
        exe.linkLibC();
    }

    const test_filter = b.option([]const u8, "test-filter", "Skip tests that do not match filter");

    const is_wine_enabled = b.option(bool, "enable-wine", "Use Wine to run cross compiled Windows tests") orelse false;
    const is_qemu_enabled = b.option(bool, "enable-qemu", "Use QEMU to run cross compiled foreign architecture tests") orelse false;
    const is_wasmtime_enabled = b.option(bool, "enable-wasmtime", "Use Wasmtime to enable and run WASI libstd tests") orelse false;
    const glibc_multi_dir = b.option([]const u8, "enable-foreign-glibc", "Provide directory with glibc installations to run cross compiled tests that link glibc");

    test_stage2.addBuildOption(bool, "is_stage1", false);
    test_stage2.addBuildOption(bool, "have_llvm", enable_llvm);
    test_stage2.addBuildOption(bool, "enable_qemu", is_qemu_enabled);
    test_stage2.addBuildOption(bool, "enable_wine", is_wine_enabled);
    test_stage2.addBuildOption(bool, "enable_wasmtime", is_wasmtime_enabled);
    test_stage2.addBuildOption(?[]const u8, "glibc_multi_install_dir", glibc_multi_dir);
    test_stage2.addBuildOption([]const u8, "version", version);

    const test_stage2_step = b.step("test-stage2", "Run the stage2 compiler tests");
    test_stage2_step.dependOn(&test_stage2.step);
    test_step.dependOn(test_stage2_step);

    var chosen_modes: [4]builtin.Mode = undefined;
    var chosen_mode_index: usize = 0;
    chosen_modes[chosen_mode_index] = builtin.Mode.Debug;
    chosen_mode_index += 1;
    if (!skip_release_safe) {
        chosen_modes[chosen_mode_index] = builtin.Mode.ReleaseSafe;
        chosen_mode_index += 1;
    }
    if (!skip_release_fast) {
        chosen_modes[chosen_mode_index] = builtin.Mode.ReleaseFast;
        chosen_mode_index += 1;
    }
    if (!skip_release_small) {
        chosen_modes[chosen_mode_index] = builtin.Mode.ReleaseSmall;
        chosen_mode_index += 1;
    }
    const modes = chosen_modes[0..chosen_mode_index];

    // run stage1 `zig fmt` on this build.zig file just to make sure it works
    test_step.dependOn(&fmt_build_zig.step);
    const fmt_step = b.step("test-fmt", "Run zig fmt against build.zig to make sure it works");
    fmt_step.dependOn(&fmt_build_zig.step);

    // TODO for the moment, skip wasm32-wasi until bugs are sorted out.
    test_step.dependOn(tests.addPkgTests(b, test_filter, "test/stage1/behavior.zig", "behavior", "Run the behavior tests", modes, false, skip_non_native, skip_libc, is_wine_enabled, is_qemu_enabled, is_wasmtime_enabled, glibc_multi_dir));

    test_step.dependOn(tests.addPkgTests(b, test_filter, "lib/std/std.zig", "std", "Run the standard library tests", modes, false, skip_non_native, skip_libc, is_wine_enabled, is_qemu_enabled, is_wasmtime_enabled, glibc_multi_dir));

    test_step.dependOn(tests.addPkgTests(b, test_filter, "lib/std/special/compiler_rt.zig", "compiler-rt", "Run the compiler_rt tests", modes, true, skip_non_native, true, is_wine_enabled, is_qemu_enabled, is_wasmtime_enabled, glibc_multi_dir));

    test_step.dependOn(tests.addCompareOutputTests(b, test_filter, modes));
    test_step.dependOn(tests.addStandaloneTests(b, test_filter, modes));
    test_step.dependOn(tests.addStackTraceTests(b, test_filter, modes));
    test_step.dependOn(tests.addCliTests(b, test_filter, modes));
    test_step.dependOn(tests.addAssembleAndLinkTests(b, test_filter, modes));
    test_step.dependOn(tests.addRuntimeSafetyTests(b, test_filter, modes));
    test_step.dependOn(tests.addTranslateCTests(b, test_filter));
    test_step.dependOn(tests.addRunTranslatedCTests(b, test_filter));
    // tests for this feature are disabled until we have the self-hosted compiler available
    // test_step.dependOn(tests.addGenHTests(b, test_filter));
    if (!skip_compile_errors) {
        test_step.dependOn(tests.addCompileErrorTests(b, test_filter, modes));
    }
    test_step.dependOn(docs_step);
}

fn dependOnLib(b: *Builder, lib_exe_obj: anytype, dep: LibraryDep) void {
    for (dep.libdirs.items) |lib_dir| {
        lib_exe_obj.addLibPath(lib_dir);
    }
    const lib_dir = fs.path.join(
        b.allocator,
        &[_][]const u8{ dep.prefix, "lib" },
    ) catch unreachable;
    for (dep.system_libs.items) |lib| {
        const static_bare_name = if (mem.eql(u8, lib, "curses"))
            @as([]const u8, "libncurses.a")
        else
            b.fmt("lib{}.a", .{lib});
        const static_lib_name = fs.path.join(
            b.allocator,
            &[_][]const u8{ lib_dir, static_bare_name },
        ) catch unreachable;
        const have_static = fileExists(static_lib_name) catch unreachable;
        if (have_static) {
            lib_exe_obj.addObjectFile(static_lib_name);
        } else {
            lib_exe_obj.linkSystemLibrary(lib);
        }
    }
    for (dep.libs.items) |lib| {
        lib_exe_obj.addObjectFile(lib);
    }
    for (dep.includes.items) |include_path| {
        lib_exe_obj.addIncludeDir(include_path);
    }
}

fn fileExists(filename: []const u8) !bool {
    fs.cwd().access(filename, .{}) catch |err| switch (err) {
        error.FileNotFound => return false,
        else => return err,
    };
    return true;
}

fn addCppLib(b: *Builder, lib_exe_obj: anytype, cmake_binary_dir: []const u8, lib_name: []const u8) void {
    lib_exe_obj.addObjectFile(fs.path.join(b.allocator, &[_][]const u8{
        cmake_binary_dir,
        "zigcpp",
        b.fmt("{}{}{}", .{ lib_exe_obj.target.libPrefix(), lib_name, lib_exe_obj.target.staticLibSuffix() }),
    }) catch unreachable);
}

const LibraryDep = struct {
    prefix: []const u8,
    libdirs: ArrayList([]const u8),
    libs: ArrayList([]const u8),
    system_libs: ArrayList([]const u8),
    includes: ArrayList([]const u8),
};

fn findLLVM(b: *Builder, llvm_config_exe: []const u8) !LibraryDep {
    const shared_mode = try b.exec(&[_][]const u8{ llvm_config_exe, "--shared-mode" });
    const is_static = mem.startsWith(u8, shared_mode, "static");
    const libs_output = if (is_static)
        try b.exec(&[_][]const u8{
            llvm_config_exe,
            "--libfiles",
            "--system-libs",
        })
    else
        try b.exec(&[_][]const u8{
            llvm_config_exe,
            "--libs",
        });
    const includes_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--includedir" });
    const libdir_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--libdir" });
    const prefix_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--prefix" });

    var result = LibraryDep{
        .prefix = mem.tokenize(prefix_output, " \r\n").next().?,
        .libs = ArrayList([]const u8).init(b.allocator),
        .system_libs = ArrayList([]const u8).init(b.allocator),
        .includes = ArrayList([]const u8).init(b.allocator),
        .libdirs = ArrayList([]const u8).init(b.allocator),
    };
    {
        var it = mem.tokenize(libs_output, " \r\n");
        while (it.next()) |lib_arg| {
            if (mem.startsWith(u8, lib_arg, "-l")) {
                try result.system_libs.append(lib_arg[2..]);
            } else {
                if (fs.path.isAbsolute(lib_arg)) {
                    try result.libs.append(lib_arg);
                } else {
                    var lib_arg_copy = lib_arg;
                    if (mem.endsWith(u8, lib_arg, ".lib")) {
                        lib_arg_copy = lib_arg[0 .. lib_arg.len - 4];
                    }
                    try result.system_libs.append(lib_arg_copy);
                }
            }
        }
    }
    {
        var it = mem.tokenize(includes_output, " \r\n");
        while (it.next()) |include_arg| {
            if (mem.startsWith(u8, include_arg, "-I")) {
                try result.includes.append(include_arg[2..]);
            } else {
                try result.includes.append(include_arg);
            }
        }
    }
    {
        var it = mem.tokenize(libdir_output, " \r\n");
        while (it.next()) |libdir| {
            if (mem.startsWith(u8, libdir, "-L")) {
                try result.libdirs.append(libdir[2..]);
            } else {
                try result.libdirs.append(libdir);
            }
        }
    }
    return result;
}

fn configureStage2(b: *Builder, exe: anytype, ctx: Context, need_cpp_includes: bool) !void {
    exe.addIncludeDir("src");
    exe.addIncludeDir(ctx.cmake_binary_dir);
    addCppLib(b, exe, ctx.cmake_binary_dir, "zigcpp");
    assert(ctx.lld_include_dir.len != 0);
    exe.addIncludeDir(ctx.lld_include_dir);
    {
        var it = mem.tokenize(ctx.lld_libraries, ";");
        while (it.next()) |lib| {
            exe.addObjectFile(lib);
        }
    }
    {
        var it = mem.tokenize(ctx.clang_libraries, ";");
        while (it.next()) |lib| {
            exe.addObjectFile(lib);
        }
    }
    dependOnLib(b, exe, ctx.llvm);

    // Boy, it sure would be nice to simply linkSystemLibrary("c++") and rely on zig's
    // ability to provide libc++ right? Well thanks to C++ not having a stable ABI this
    // will cause linker errors. It would work in the situation when `zig cc` is used to
    // build LLVM, Clang, and LLD, however when depending on them as system libraries, system
    // libc++ must be used.
    const cross_compile = false; // TODO
    if (cross_compile) {
        // In this case we assume that zig cc was used to build the LLVM, Clang, LLD dependencies.
        exe.linkSystemLibrary("c++");
    } else {
        if (exe.target.getOsTag() == .linux) {
            // First we try to static link against gcc libstdc++. If that doesn't work,
            // we fall back to -lc++ and cross our fingers.
            addCxxKnownPath(b, ctx, exe, "libstdc++.a", "", need_cpp_includes) catch |err| switch (err) {
                error.RequiredLibraryNotFound => {
                    exe.linkSystemLibrary("c++");
                },
                else => |e| return e,
            };

            exe.linkSystemLibrary("pthread");
        } else if (exe.target.isFreeBSD()) {
            try addCxxKnownPath(b, ctx, exe, "libc++.a", null, need_cpp_includes);
            exe.linkSystemLibrary("pthread");
        } else if (exe.target.isDarwin()) {
            if (addCxxKnownPath(b, ctx, exe, "libgcc_eh.a", "", need_cpp_includes)) {
                // Compiler is GCC.
                try addCxxKnownPath(b, ctx, exe, "libstdc++.a", null, need_cpp_includes);
                exe.linkSystemLibrary("pthread");
                // TODO LLD cannot perform this link.
                // See https://github.com/ziglang/zig/issues/1535
                exe.enableSystemLinkerHack();
            } else |err| switch (err) {
                error.RequiredLibraryNotFound => {
                    // System compiler, not gcc.
                    exe.linkSystemLibrary("c++");
                },
                else => |e| return e,
            }
        }

        if (ctx.dia_guids_lib.len != 0) {
            exe.addObjectFile(ctx.dia_guids_lib);
        }
    }
}

fn addCxxKnownPath(
    b: *Builder,
    ctx: Context,
    exe: anytype,
    objname: []const u8,
    errtxt: ?[]const u8,
    need_cpp_includes: bool,
) !void {
    const path_padded = try b.exec(&[_][]const u8{
        ctx.cxx_compiler,
        b.fmt("-print-file-name={}", .{objname}),
    });
    const path_unpadded = mem.tokenize(path_padded, "\r\n").next().?;
    if (mem.eql(u8, path_unpadded, objname)) {
        if (errtxt) |msg| {
            warn("{}", .{msg});
        } else {
            warn("Unable to determine path to {}\n", .{objname});
        }
        return error.RequiredLibraryNotFound;
    }
    exe.addObjectFile(path_unpadded);

    // TODO a way to integrate with system c++ include files here
    // cc -E -Wp,-v -xc++ /dev/null
    if (need_cpp_includes) {
        // I used these temporarily for testing something but we obviously need a
        // more general purpose solution here.
        //exe.addIncludeDir("/nix/store/b3zsk4ihlpiimv3vff86bb5bxghgdzb9-gcc-9.2.0/lib/gcc/x86_64-unknown-linux-gnu/9.2.0/../../../../include/c++/9.2.0");
        //exe.addIncludeDir("/nix/store/b3zsk4ihlpiimv3vff86bb5bxghgdzb9-gcc-9.2.0/lib/gcc/x86_64-unknown-linux-gnu/9.2.0/../../../../include/c++/9.2.0/x86_64-unknown-linux-gnu");
        //exe.addIncludeDir("/nix/store/b3zsk4ihlpiimv3vff86bb5bxghgdzb9-gcc-9.2.0/lib/gcc/x86_64-unknown-linux-gnu/9.2.0/../../../../include/c++/9.2.0/backward");
    }
}

const Context = struct {
    cmake_binary_dir: []const u8,
    cxx_compiler: []const u8,
    llvm_config_exe: []const u8,
    lld_include_dir: []const u8,
    lld_libraries: []const u8,
    clang_libraries: []const u8,
    dia_guids_lib: []const u8,
    llvm: LibraryDep,
};

const max_config_h_bytes = 1 * 1024 * 1024;

fn findAndReadConfigH(b: *Builder) ![]const u8 {
    var check_dir = fs.path.dirname(b.zig_exe).?;
    while (true) {
        var dir = try fs.cwd().openDir(check_dir, .{});
        defer dir.close();

        const config_h_text = dir.readFileAlloc(b.allocator, "config.h", max_config_h_bytes) catch |err| switch (err) {
            error.FileNotFound => {
                const new_check_dir = fs.path.dirname(check_dir);
                if (new_check_dir == null or mem.eql(u8, new_check_dir.?, check_dir)) {
                    std.debug.warn("Unable to find config.h file relative to Zig executable.\n", .{});
                    std.debug.warn("`zig build` must be run using a Zig executable within the source tree.\n", .{});
                    std.process.exit(1);
                }
                check_dir = new_check_dir.?;
                continue;
            },
            else => |e| return e,
        };
        return config_h_text;
    } else unreachable; // TODO should not need `else unreachable`.
}

fn parseConfigH(b: *Builder, config_h_text: []const u8) Context {
    var ctx: Context = .{
        .cmake_binary_dir = undefined,
        .cxx_compiler = undefined,
        .llvm_config_exe = undefined,
        .lld_include_dir = undefined,
        .lld_libraries = undefined,
        .clang_libraries = undefined,
        .dia_guids_lib = undefined,
        .llvm = undefined,
    };

    const mappings = [_]struct { prefix: []const u8, field: []const u8 }{
        .{
            .prefix = "#define ZIG_CMAKE_BINARY_DIR ",
            .field = "cmake_binary_dir",
        },
        .{
            .prefix = "#define ZIG_CXX_COMPILER ",
            .field = "cxx_compiler",
        },
        .{
            .prefix = "#define ZIG_LLD_INCLUDE_PATH ",
            .field = "lld_include_dir",
        },
        .{
            .prefix = "#define ZIG_LLD_LIBRARIES ",
            .field = "lld_libraries",
        },
        .{
            .prefix = "#define ZIG_CLANG_LIBRARIES ",
            .field = "clang_libraries",
        },
        .{
            .prefix = "#define ZIG_LLVM_CONFIG_EXE ",
            .field = "llvm_config_exe",
        },
        .{
            .prefix = "#define ZIG_DIA_GUIDS_LIB ",
            .field = "dia_guids_lib",
        },
    };

    var lines_it = mem.tokenize(config_h_text, "\r\n");
    while (lines_it.next()) |line| {
        inline for (mappings) |mapping| {
            if (mem.startsWith(u8, line, mapping.prefix)) {
                var it = mem.split(line, "\"");
                _ = it.next().?; // skip the stuff before the quote
                const quoted = it.next().?; // the stuff inside the quote
                @field(ctx, mapping.field) = toNativePathSep(b, quoted);
            }
        }
    }
    return ctx;
}

fn toNativePathSep(b: *Builder, s: []const u8) []u8 {
    const duplicated = mem.dupe(b.allocator, u8, s) catch unreachable;
    for (duplicated) |*byte| switch (byte.*) {
        '/' => byte.* = fs.path.sep,
        else => {},
    };
    return duplicated;
}