[Client] Add support for zig client library

clients/zig/.gitignore

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+.zig-cache/*
+zig-out/*

clients/zig/Makefile

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+
+
+.PHONY: test coverage run run-ex build-ex
+
+
+test: test-cac test-expt
+
+test-cac:
+	zig test -I../../headers -lc  src/cac.zig ../../target/debug/libcac_client.so
+
+test-expt:
+	zig test -I../../headers -lc  src/expt.zig ../../target/debug/libexperimentation_client.so
+
+
+run-ex: build-ex
+	./zig-out/bin/cli
+
+build-ex:
+	zig build
+

clients/zig/README.md

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+### Pauli
+
+A zig based client SDK for [`superposition`](https://github.com/juspay/superposition) service.
+
+### Pre-requisites
+
+-   As this client leverages `build.zig.zon` file for managing dependencies. Your zig version should atleast satisfy the minimum version mentioned in the `build.zig.zon` file.
+-   You should have `superposition` service running on your local machine or on a remote server. (This is optional in the initial development phase, but might be required for testing)
+-   The build steps consist of the following steps:
+    -   Pulling the superposition repository, this implies that you have `git` installed on your machine and you have access to the repository.
+    -   This is followed by the build stage of `superposition`. (required to get the shared library) `rust` and `cargo` should be installed on your machine for this stage to complete.
+
+### Get Started
+
+-   To get started with the client, create your own zig project:
+    ```bash
+    mkdir my_project
+    cd my_project
+    zig init-exe
+    ```
+-   To install the client as a dependency run the following command:
+    ```bash
+    zig fetch --save <url/path>
+    ```
+    Here, the URL can be the place where the zig client is hosted or the path to the client on your local machine.
+    The url/path should allow the zig build system to discover the `build.zig.zon` file and the paths included within it.

clients/zig/build.zig

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+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 {
+    const target = b.standardTargetOptions(.{});
+
+    const optimize = b.standardOptimizeOption(.{});
+
+    const superposition = buildSuperpositionClient(b);
+
+    const lib = b.addStaticLibrary(.{
+        .name = "pauli",
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    lib.step.dependOn(&superposition.step);
+
+    linkBindingsDebug(b, lib);
+
+    b.installArtifact(lib);
+
+    // Tests section
+
+    const test_step = b.step("test", "Run unit tests");
+
+    // Root Tests
+
+    const lib_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    lib_unit_tests.step.dependOn(&superposition.step);
+
+    linkBindingsDebug(b, lib_unit_tests);
+
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+    test_step.dependOn(&run_lib_unit_tests.step);
+
+    const module = b.addModule("pauli", .{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    module.linkLibrary(lib);
+
+    module.addIncludePath(b.path("superposition/headers"));
+    module.addLibraryPath(b.path("superposition/target/release"));
+
+    module.linkSystemLibrary("c", .{});
+
+    module.linkSystemLibrary("cac_client", .{});
+    module.linkSystemLibrary("experimentation_client", .{});
+}
+
+fn linkBindingsDebug(b: *std.Build, c: *std.Build.Step.Compile) void {
+    c.addIncludePath(b.path("superposition/headers"));
+    c.addLibraryPath(b.path("superposition/target/release"));
+
+    c.linkLibC();
+    c.linkSystemLibrary("cac_client");
+    c.linkSystemLibrary("experimentation_client");
+}
+
+fn buildSuperpositionClient(b: *std.Build) *std.Build.Step.Run {
+    const repository = b.addSystemCommand(&.{
+        "sh", "-c", std.fmt.comptimePrint(
+            \\if [ ! -d superposition ]; then
+            \\   git clone https://github.com/juspay/superposition.git
+            \\fi
+        , .{}),
+    });
+
+    const rust_build = b.addSystemCommand(&.{ "cargo", "build", "--release" });
+
+    rust_build.setCwd(b.path("superposition"));
+
+    rust_build.step.dependOn(&repository.step);
+
+    return rust_build;
+}

clients/zig/build.zig.zon

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+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = "pauli",
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        "README.md",
+    },
+}

clients/zig/example/.gitignore

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+.zig-cache/*
+zig-out/*

clients/zig/example/build.zig

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+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(.{});
+
+    const package = b.dependency("pauli", .{
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const module = package.module("pauli");
+
+    const exe = b.addExecutable(.{
+        .name = "example",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    exe.root_module.addImport("pauli", module);
+
+    // 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 *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_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    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);
+}

clients/zig/example/build.zig.zon

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+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = "example",
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        .pauli = .{
+            .url = "../",
+            .hash = "12206eb33ebbd1b0936dcb84d44460da9a863150e60e2432cef3ddf3fb6fd75a2f09",
+        },
+    },
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}

clients/zig/example/src/main.zig

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+const cac_client = @import("pauli").cac;
+const std = @import("std");
+
+pub fn main() !void {
+    var logging_alloc = std.heap.loggingAllocator(std.heap.page_allocator);
+    const alloc = logging_alloc.allocator();
+
+    const setup_config = cac_client.SetupConfig{ .tenant = "public", .update_frequency = 10, .hostname = "http://localhost:8080" };
+
+    const client = try cac_client.Client.init(setup_config);
+
+    std.log.info("Client Initialized", .{});
+
+    const input = [_][]const u8{"test"};
+
+    const config = struct { test_2: u8 };
+
+    const output_1 = try client.getDefaultConfig(config, alloc, &input);
+    std.log.info("Output: {}", .{output_1});
+}