sources.nix

# Functions for copying sources to the Nix store.
{ lib }:

let
  inherit (builtins)
    hasContext
    match
    readDir
    split
    storeDir
    tryEval
    ;
  inherit (lib)
    filter
    getAttr
    isString
    pathExists
    readFile
    ;
in
rec {

  # Returns the type of a path: regular (for file), symlink, or directory
  pathType = p: getAttr (baseNameOf p) (readDir (dirOf p));

  # Returns true if the path exists and is a directory, false otherwise
  pathIsDirectory = p: if pathExists p then (pathType p) == "directory" else false;

  # Returns true if the path exists and is a regular file, false otherwise
  pathIsRegularFile = p: if pathExists p then (pathType p) == "regular" else false;

  # Bring in a path as a source, filtering out all Subversion and CVS
  # directories, as well as backup files (*~).
  cleanSourceFilter = name: type: let baseName = baseNameOf (toString name); in ! (
    # Filter out version control software files/directories
    (baseName == ".git" || type == "directory" && (baseName == ".svn" || baseName == "CVS" || baseName == ".hg")) ||
    # Filter out editor backup / swap files.
    lib.hasSuffix "~" baseName ||
    match "^\\.sw[a-z]$" baseName != null ||
    match "^\\..*\\.sw[a-z]$" baseName != null ||

    # Filter out generates files.
    lib.hasSuffix ".o" baseName ||
    lib.hasSuffix ".so" baseName ||
    # Filter out nix-build result symlinks
    (type == "symlink" && lib.hasPrefix "result" baseName)
  );

  # Filters a source tree removing version control files and directories using cleanSourceWith
  #
  # Example:
  #          cleanSource ./.
  cleanSource = src: cleanSourceWith { filter = cleanSourceFilter; inherit src; };

  # Like `builtins.filterSource`, except it will compose with itself,
  # allowing you to chain multiple calls together without any
  # intermediate copies being put in the nix store.
  #
  #     lib.cleanSourceWith {
  #       filter = f;
  #       src = lib.cleanSourceWith {
  #         filter = g;
  #         src = ./.;
  #       };
  #     }
  #     # Succeeds!
  #
  #     builtins.filterSource f (builtins.filterSource g ./.)
  #     # Fails!
  #
  # Parameters:
  #
  #   src:      A path or cleanSourceWith result to filter and/or rename.
  #
  #   filter:   A function (path -> type -> bool)
  #             Optional with default value: constant true (include everything)
  #             The function will be combined with the && operator such
  #             that src.filter is called lazily.
  #             For implementing a filter, see
  #             https://nixos.org/nix/manual/#builtin-filterSource
  #
  #   name:     Optional name to use as part of the store path.
  #             This defaults to `src.name` or otherwise `"source"`.
  #
  cleanSourceWith = { filter ? _path: _type: true, src, name ? null }:
    let
      isFiltered = src ? _isLibCleanSourceWith;
      origSrc = if isFiltered then src.origSrc else src;
      filter' = if isFiltered then name: type: filter name type && src.filter name type else filter;
      name' = if name != null then name else if isFiltered then src.name else "source";
    in {
      inherit origSrc;
      filter = filter';
      outPath = builtins.path { filter = filter'; path = origSrc; name = name'; };
      _isLibCleanSourceWith = true;
      name = name';
    };

  # Filter sources by a list of regular expressions.
  #
  # E.g. `src = sourceByRegex ./my-subproject [".*\.py$" "^database.sql$"]`
  sourceByRegex = src: regexes:
    let
      isFiltered = src ? _isLibCleanSourceWith;
      origSrc = if isFiltered then src.origSrc else src;
    in lib.cleanSourceWith {
      filter = (path: type:
        let relPath = lib.removePrefix (toString origSrc + "/") (toString path);
        in lib.any (re: match re relPath != null) regexes);
      inherit src;
    };

  # Get all files ending with the specified suffices from the given
  # directory or its descendants.  E.g. `sourceFilesBySuffices ./dir
  # [".xml" ".c"]'.
  sourceFilesBySuffices = path: exts:
    let filter = name: type:
      let base = baseNameOf (toString name);
      in type == "directory" || lib.any (ext: lib.hasSuffix ext base) exts;
    in cleanSourceWith { inherit filter; src = path; };

  pathIsGitRepo = path: (tryEval (commitIdFromGitRepo path)).success;

  # Get the commit id of a git repo
  # Example: commitIdFromGitRepo <nixpkgs/.git>
  commitIdFromGitRepo =
    let readCommitFromFile = file: path:
        let fileName       = toString path + "/" + file;
            packedRefsName = toString path + "/packed-refs";
            absolutePath   = base: path:
              if lib.hasPrefix "/" path
              then path
              else toString (/. + "${base}/${path}");
        in if pathIsRegularFile path
           # Resolve git worktrees. See gitrepository-layout(5)
           then
             let m   = match "^gitdir: (.*)$" (lib.fileContents path);
             in if m == null
                then throw ("File contains no gitdir reference: " + path)
                else
                  let gitDir     = absolutePath (dirOf path) (lib.head m);
                      commonDir' = if pathIsRegularFile "${gitDir}/commondir"
                                   then lib.fileContents "${gitDir}/commondir"
                                   else gitDir;
                      commonDir  = absolutePath gitDir commonDir';
                      refFile    = lib.removePrefix "${commonDir}/" "${gitDir}/${file}";
                  in readCommitFromFile refFile commonDir

           else if pathIsRegularFile fileName
           # Sometimes git stores the commitId directly in the file but
           # sometimes it stores something like: «ref: refs/heads/branch-name»
           then
             let fileContent = lib.fileContents fileName;
                 matchRef    = match "^ref: (.*)$" fileContent;
             in if  matchRef == null
                then fileContent
                else readCommitFromFile (lib.head matchRef) path

           else if pathIsRegularFile packedRefsName
           # Sometimes, the file isn't there at all and has been packed away in the
           # packed-refs file, so we have to grep through it:
           then
             let fileContent = readFile packedRefsName;
                 matchRef = match "([a-z0-9]+) ${file}";
                 isRef = s: isString s && (matchRef s) != null;
                 # there is a bug in libstdc++ leading to stackoverflow for long strings:
                 # https://github.com/NixOS/nix/issues/2147#issuecomment-659868795
                 refs = filter isRef (split "\n" fileContent);
             in if refs == []
                then throw ("Could not find " + file + " in " + packedRefsName)
                else lib.head (matchRef (lib.head refs))

           else throw ("Not a .git directory: " + path);
    in readCommitFromFile "HEAD";

  pathHasContext = builtins.hasContext or (lib.hasPrefix storeDir);

  canCleanSource = src: src ? _isLibCleanSourceWith || !(pathHasContext (toString src));
}