const std = @import("std");
const builtin = @import("builtin");

// 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(.{});

    // Create a module for lambda.zig
    const lambda_module = b.createModule(.{
        .root_source_file = b.path("src/lambda.zig"),
        .target = target,
        .optimize = optimize,
    });

    const lib = b.addLibrary(.{
        .name = "lambda-zig",
        .linkage = .static,
        .root_module = lambda_module,
    });

    // Export the module for other packages to use
    _ = b.addModule("lambda_runtime", .{
        .root_source_file = b.path("src/lambda.zig"),
        .target = target,
        .optimize = optimize,
    });

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

    // Creates a step for unit testing. This only builds the test executable
    // but does not run it.
    const test_module = b.createModule(.{
        .root_source_file = b.path("src/lambda.zig"),
        .target = target,
        .optimize = optimize,
    });

    const main_tests = b.addTest(.{
        .name = "test",
        .root_module = test_module,
    });

    const run_main_tests = b.addRunArtifact(main_tests);

    // Build the lambda-build CLI to ensure it compiles
    // This catches dependency version mismatches between tools/build and the main project
    const lambda_build_dep = b.dependency("lambda_build", .{
        .target = b.graph.host,
        .optimize = optimize,
    });
    const lambda_build_exe = lambda_build_dep.artifact("lambda-build");

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

    // Create executable module
    const exe_module = b.createModule(.{
        .root_source_file = b.path("src/sample-main.zig"),
        .target = target,
        .optimize = optimize,
    });

    const exe = b.addExecutable(.{
        .name = "custom",
        .root_module = exe_module,
    });

    b.installArtifact(exe);
    try configureBuildInternal(b, exe);
}

/// Internal version of configureBuild for lambda-zig's own build.
///
/// Both this and configureBuild do the same thing, but resolve the lambda_build
/// dependency differently:
///
/// - Here: we call `b.dependency("lambda_build", ...)` directly since `b` is
///   lambda-zig's own Build context, which has lambda_build in its build.zig.zon
///
/// - configureBuild: consumers pass in their lambda_zig dependency, and we use
///   `lambda_zig_dep.builder.dependency("lambda_build", ...)` to resolve it from
///   lambda-zig's build.zig.zon rather than the consumer's
///
/// This avoids requiring consumers to declare lambda_build as a transitive
/// dependency in their own build.zig.zon.
fn configureBuildInternal(b: *std.Build, exe: *std.Build.Step.Compile) !void {
    // When called from lambda-zig's own build, use local dependency
    const lambda_build_dep = b.dependency("lambda_build", .{
        .target = b.graph.host,
        .optimize = .ReleaseSafe,
    });
    try @import("lambdabuild.zig").configureBuild(b, lambda_build_dep, exe);
}

/// Configure Lambda build steps for a Zig project.
///
/// This function adds build steps and options for packaging and deploying
/// Lambda functions to AWS. The `lambda_zig_dep` parameter must be the
/// dependency object obtained from `b.dependency("lambda_zig", ...)`.
///
/// ## Build Steps
///
/// The following build steps are added:
///
/// - `awslambda_package`: Package the executable into a Lambda deployment zip
/// - `awslambda_iam`: Create or verify the IAM role for the Lambda function
/// - `awslambda_deploy`: Deploy the function to AWS Lambda (depends on package)
/// - `awslambda_run`: Invoke the deployed function (depends on deploy)
///
/// ## Build Options
///
/// The following options are added to the build:
///
/// - `-Dfunction-name=[string]`: Name of the Lambda function (default: "zig-fn")
/// - `-Dregion=[string]`: AWS region for deployment and invocation
/// - `-Dprofile=[string]`: AWS profile to use for credentials
/// - `-Drole-name=[string]`: IAM role name (default: "lambda_basic_execution")
/// - `-Dpayload=[string]`: JSON payload for invocation (default: "{}")
///
/// ## Example
///
/// ```zig
/// const lambda_zig = @import("lambda_zig");
///
/// pub fn build(b: *std.Build) !void {
///     const target = b.standardTargetOptions(.{});
///     const optimize = b.standardOptimizeOption(.{});
///
///     const lambda_zig_dep = b.dependency("lambda_zig", .{
///         .target = target,
///         .optimize = optimize,
///     });
///
///     const exe = b.addExecutable(.{ ... });
///     b.installArtifact(exe);
///
///     try lambda_zig.configureBuild(b, lambda_zig_dep, exe);
/// }
/// ```
pub fn configureBuild(b: *std.Build, lambda_zig_dep: *std.Build.Dependency, exe: *std.Build.Step.Compile) !void {
    // Get lambda_build from the lambda_zig dependency's Build context
    const lambda_build_dep = lambda_zig_dep.builder.dependency("lambda_build", .{
        .target = b.graph.host,
        .optimize = .ReleaseSafe,
    });
    try @import("lambdabuild.zig").configureBuild(b, lambda_build_dep, exe);
}