nixos-config/resolve-jobs.nix

# Compatibility function to allow flakes to be used by
# non-flake-enabled Nix versions. Given a source tree containing a
# 'flake.nix' and 'flake.lock' file, it fetches the flake inputs and
# calls the flake's 'outputs' function. It then returns an attrset
# containing 'defaultNix' (to be used in 'default.nix'), 'shellNix'
# (to be used in 'shell.nix').

{ ... }:

let

  flake_compat = src:
    let

      lockFilePath = src + "/flake.lock";

      lockFile = builtins.fromJSON (builtins.readFile lockFilePath);

      fetchTree =
        info:
        if info.type == "github" then
          {
            outPath =
              fetchTarball
                ({ url = "https://api.${info.host or "github.com"}/repos/${info.owner}/${info.repo}/tarball/${info.rev}"; }
                  // (if info ? narHash then { sha256 = info.narHash; } else { })
                );
            rev = info.rev;
            shortRev = builtins.substring 0 7 info.rev;
            lastModified = info.lastModified;
            lastModifiedDate = formatSecondsSinceEpoch info.lastModified;
            narHash = info.narHash;
          }
        else if info.type == "git" then
          {
            outPath =
              builtins.fetchGit
                ({ url = info.url; }
                // (if info ? rev then { inherit (info) rev; } else { })
                // (if info ? ref then { inherit (info) ref; } else { })
                // (if info ? submodules then { inherit (info) submodules; } else { })
                );
            lastModified = info.lastModified;
            lastModifiedDate = formatSecondsSinceEpoch info.lastModified;
            narHash = info.narHash;
          } // (if info ? rev then {
            rev = info.rev;
            shortRev = builtins.substring 0 7 info.rev;
          } else { })
        else if info.type == "path" then
          {
            outPath = builtins.path { path = info.path; };
            narHash = info.narHash;
          }
        else if info.type == "tarball" then
          {
            outPath =
              fetchTarball
                ({ inherit (info) url; }
                  // (if info ? narHash then { sha256 = info.narHash; } else { })
                );
          }
        else if info.type == "gitlab" then
          {
            inherit (info) rev narHash lastModified;
            outPath =
              fetchTarball
                ({ url = "https://${info.host or "gitlab.com"}/api/v4/projects/${info.owner}%2F${info.repo}/repository/archive.tar.gz?sha=${info.rev}"; }
                  // (if info ? narHash then { sha256 = info.narHash; } else { })
                );
            shortRev = builtins.substring 0 7 info.rev;
          }
        else
        # FIXME: add Mercurial, tarball inputs.
          throw "flake input has unsupported input type '${info.type}'";

      callFlake4 = flakeSrc: locks:
        let
          flake = import (flakeSrc + "/flake.nix");

          inputs = builtins.mapAttrs
            (n: v:
              if v.flake or true
              then callFlake4 (fetchTree (v.locked // v.info)) v.inputs
              else fetchTree (v.locked // v.info))
            locks;

          outputs = flakeSrc // (flake.outputs (inputs // { self = outputs; }));
        in
        assert flake.edition == 201909;
        outputs;

      callLocklessFlake = flakeSrc:
        let
          flake = import (flakeSrc + "/flake.nix");
          outputs = flakeSrc // (flake.outputs ({ self = outputs; }));
        in
        outputs;

      rootSrc =
        let
          # Try to clean the source tree by using fetchGit, if this source
          # tree is a valid git repository.
          tryFetchGit = src:
            if isGit && !isShallow
            then
              let res = builtins.fetchGit src;
              in if res.rev == "0000000000000000000000000000000000000000" then removeAttrs res [ "rev" "shortRev" ] else res
            else { outPath = src; };
          # NB git worktrees have a file for .git, so we don't check the type of .git
          isGit = builtins.pathExists (src + "/.git");
          isShallow = builtins.pathExists (src + "/.git/shallow");

        in
        { lastModified = 0; lastModifiedDate = formatSecondsSinceEpoch 0; }
        // (if src ? outPath then src else tryFetchGit src);

      # Format number of seconds in the Unix epoch as %Y%m%d%H%M%S.
      formatSecondsSinceEpoch = t:
        let
          rem = x: y: x - x / y * y;
          days = t / 86400;
          secondsInDay = rem t 86400;
          hours = secondsInDay / 3600;
          minutes = (rem secondsInDay 3600) / 60;
          seconds = rem t 60;

          # Courtesy of https://stackoverflow.com/a/32158604.
          z = days + 719468;
          era = (if z >= 0 then z else z - 146096) / 146097;
          doe = z - era * 146097;
          yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
          y = yoe + era * 400;
          doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
          mp = (5 * doy + 2) / 153;
          d = doy - (153 * mp + 2) / 5 + 1;
          m = mp + (if mp < 10 then 3 else -9);
          y' = y + (if m <= 2 then 1 else 0);

          pad = s: if builtins.stringLength s < 2 then "0" + s else s;
        in
        "${toString y'}${pad (toString m)}${pad (toString d)}${pad (toString hours)}${pad (toString minutes)}${pad (toString seconds)}";

      allNodes =
        builtins.mapAttrs
          (key: node:
            let
              sourceInfo =
                if key == lockFile.root
                then rootSrc
                else fetchTree (node.info or { } // removeAttrs node.locked [ "dir" ]);

              subdir = if key == lockFile.root then "" else node.locked.dir or "";

              flake = import (sourceInfo + (if subdir != "" then "/" else "") + subdir + "/flake.nix");

              inputs = builtins.mapAttrs
                (inputName: inputSpec: allNodes.${resolveInput inputSpec})
                (node.inputs or { });

              # Resolve a input spec into a node name. An input spec is
              # either a node name, or a 'follows' path from the root
              # node.
              resolveInput = inputSpec:
                if builtins.isList inputSpec
                then getInputByPath lockFile.root inputSpec
                else inputSpec;

              # Follow an input path (e.g. ["dwarffs" "nixpkgs"]) from the
              # root node, returning the final node.
              getInputByPath = nodeName: path:
                if path == [ ]
                then nodeName
                else
                  getInputByPath
                    # Since this could be a 'follows' input, call resolveInput.
                    (resolveInput lockFile.nodes.${nodeName}.inputs.${builtins.head path})
                    (builtins.tail path);

              outputs = flake.outputs (inputs // { self = result; });

              result = outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; };
            in
            if node.flake or true then
              assert builtins.isFunction flake.outputs;
              result
            else
              sourceInfo
          )
          lockFile.nodes;

      result =
        if !(builtins.pathExists lockFilePath)
        then callLocklessFlake rootSrc
        else if lockFile.version == 4
        then callFlake4 rootSrc (lockFile.inputs)
        else if lockFile.version >= 5 && lockFile.version <= 7
        then allNodes.${lockFile.root}
        else throw "lock file '${lockFilePath}' has unsupported version ${toString lockFile.version}";
    in
    result.hydraJobs;



  prs = builtins.fromJSON (builtins.readFile <prs>);
  srcs = builtins.mapAttrs
    (n: value:
      builtins.fetchgit {
        url = "https://github.com/${value.base.repo.owner}/${value.base.repo.name}";
        ref = "pulls/${n}/head";
      }
    )
    prs;
in
builtins.mapAttrs (_: flake_compat) srcs