From 8c08b67be3bcc7a0dd19cc43cebb58ede2e12ed5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20DOUIN?= <clement.douin@posteo.net>
Date: Sat, 23 Nov 2024 14:06:32 +0100
Subject: [PATCH] refactor cross systems structure

---
 .github/workflows/pre-release.yml |  6 +++---
 cross-systems.nix                 | 31 ++++++++++++++++++++------
 default.nix                       | 36 +++++++++++++++----------------
 3 files changed, 46 insertions(+), 27 deletions(-)

diff --git a/.github/workflows/pre-release.yml b/.github/workflows/pre-release.yml
index 814056c5..d1b38a28 100644
--- a/.github/workflows/pre-release.yml
+++ b/.github/workflows/pre-release.yml
@@ -11,15 +11,15 @@ jobs:
       matrix:
         include:
           - os: ubuntu-latest
-            target:
+            target: x86_64-unknown-linux-musl
           - os: ubuntu-latest
             target: aarch64-unknown-linux-musl
           - os: ubuntu-latest
             target: x86_64-pc-windows-gnu
           - os: macos-13
-            target:
+            target: x86_64-apple-darwin
           - os: macos-14
-            target:
+            target: aarch64-apple-darwin
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
diff --git a/cross-systems.nix b/cross-systems.nix
index eda5a252..7416a4e3 100644
--- a/cross-systems.nix
+++ b/cross-systems.nix
@@ -1,11 +1,30 @@
+# The first level represents the build platform system, and the second
+# level represents the build platform triple config.
+
 {
-  aarch64-unknown-linux-musl = {
-    runner = { qemu, ... }: "${qemu}/bin/qemu-aarch64 ./himalaya";
+  x86_64-linux = {
+    x86_64-unknown-linux-musl = { };
+
+    aarch64-unknown-linux-musl = {
+      runner = { qemu, ... }: "${qemu}/bin/qemu-aarch64 ./himalaya";
+    };
+
+    x86_64-pc-windows-gnu = {
+      runner = { wine, ... }:
+        let wine64 = wine.override { wineBuild = "wine64"; };
+        in "${wine64}/bin/wine64 ./himalaya.exe";
+    };
   };
 
-  x86_64-pc-windows-gnu = {
-    runner = { wine, ... }:
-      let wine64 = wine.override { wineBuild = "wine64"; };
-      in "${wine64}/bin/wine64 ./himalaya.exe";
+  aarch64-linux = {
+    x86_64-unknown-linux-musl = { };
+  };
+
+  x86_64-darwin = {
+    x86_64-apple-darwin = { };
+  };
+
+  aarch64-darwin = {
+    aarch64-apple-darwin = { };
   };
 }  
diff --git a/default.nix b/default.nix
index 0fe3a3ed..617c6b10 100644
--- a/default.nix
+++ b/default.nix
@@ -1,43 +1,43 @@
-# https://nixos.org/manual/nixpkgs/stable/#sec-cross-usage
-{ crossSystem ? null }:
+{ target ? null }:
 
 let
-  crossBuildEnabled = crossSystem != null && crossSystem != "";
+  pkgs = import <nixpkgs> { };
+  crossPkgs = if isNull target then pkgs else import <nixpkgs> { crossSystem.config = target; };
   crossSystems = import ./cross-systems.nix;
 
-  buildPkgs = import <nixpkgs> { };
-  hostPkgs = if crossBuildEnabled then import <nixpkgs> { inherit crossSystem; } else buildPkgs;
+  inherit (crossPkgs.stdenv) buildPlatform hostPlatform;
 
-  inherit (hostPkgs.stdenv) buildPlatform hostPlatform;
+  crossSystem = crossSystems.${buildPlatform.system}.${hostPlatform.config}
+    or throw ("Platform not supported: " + hostPlatform.config);
 
-  runner = if crossBuildEnabled then crossSystems.${hostPlatform.config}.runner buildPkgs else "./himalaya";
+  runner = crossSystem.runner or (_: "./himalaya") pkgs;
 
   fenix = import (fetchTarball "https://github.com/soywod/fenix/archive/main.tar.gz") { };
 
   mkToolchain = import ./rust-toolchain.nix fenix;
 
   rustToolchain = mkToolchain.fromTarget {
-    pkgs = hostPkgs;
+    pkgs = crossPkgs;
     targetSystem = buildPlatform.config;
   };
 
-  rustPlatform = hostPkgs.makeRustPlatform {
+  rustPlatform = crossPkgs.makeRustPlatform {
     rustc = rustToolchain;
     cargo = rustToolchain;
   };
 
   himalaya = import ./package.nix {
     inherit rustPlatform;
-    lib = hostPkgs.lib;
-    fetchFromGitHub = hostPkgs.fetchFromGitHub;
-    pkg-config = hostPkgs.pkg-config;
-    darwin = hostPkgs.darwin;
+    lib = crossPkgs.lib;
+    fetchFromGitHub = crossPkgs.fetchFromGitHub;
+    pkg-config = crossPkgs.pkg-config;
+    darwin = crossPkgs.darwin;
     installShellFiles = false;
     installShellCompletions = false;
     installManPages = false;
-    notmuch = hostPkgs.notmuch;
-    gpgme = hostPkgs.gpgme;
-    stdenv = hostPkgs.stdenv;
+    notmuch = crossPkgs.notmuch;
+    gpgme = crossPkgs.gpgme;
+    stdenv = crossPkgs.stdenv;
   };
 in
 
@@ -59,10 +59,10 @@ himalaya.overrideAttrs (drv: {
     tar -czf himalaya.tgz himalaya* share
     mv himalaya.tgz ../
 
-    ${hostPkgs.zip}/bin/zip -r himalaya.zip himalaya* share
+    ${crossPkgs.zip}/bin/zip -r himalaya.zip himalaya* share
     mv himalaya.zip ../
   '';
-  src = hostPkgs.nix-gitignore.gitignoreSource [ ] ./.;
+  src = crossPkgs.nix-gitignore.gitignoreSource [ ] ./.;
   cargoDeps = rustPlatform.importCargoLock {
     lockFile = ./Cargo.lock;
     allowBuiltinFetchGit = true;