# Functions for copying sources to the Nix store.
{lib}:
# Tested in lib/tests/sources.sh
let
  inherit
    (builtins)
    hasContext
    match
    readDir
    split
    storeDir
    tryEval
    ;
  inherit
    (lib)
    boolToString
    filter
    getAttr
    isString
    pathExists
    readFile
    ;

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

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

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

  /*
   A basic filter for `cleanSourceWith` that removes
   directories of version control system, backup files (*~)
   and some generated 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)
      ||
      # Filter out sockets and other types of files we can't have in the store.
      (type == "unknown")
    );

  /*
   Filters a source tree removing version control files and directories using cleanSourceFilter.
   
   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.
   
   Example:
       lib.cleanSourceWith {
         filter = f;
         src = lib.cleanSourceWith {
           filter = g;
           src = ./.;
         };
       }
       # Succeeds!
   
       builtins.filterSource f (builtins.filterSource g ./.)
       # Fails!
   
   */
  cleanSourceWith = {
    # A path or cleanSourceWith result to filter and/or rename.
    src,
    # 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
    # Type: A function (path -> type -> bool)
    filter ? _path: _type: true,
    # Optional name to use as part of the store path.
    # This defaults to `src.name` or otherwise `"source"`.
    name ? null,
  }: let
    orig = toSourceAttributes src;
  in
    fromSourceAttributes {
      inherit (orig) origSrc;
      filter = path: type: filter path type && orig.filter path type;
      name =
        if name != null
        then name
        else orig.name;
    };

  /*
   Add logging to a source, for troubleshooting the filtering behavior.
   Type:
     sources.trace :: sourceLike -> Source
   */
  trace =
    # Source to debug. The returned source will behave like this source, but also log its filter invocations.
    src: let
      attrs = toSourceAttributes src;
    in
      fromSourceAttributes (
        attrs
        // {
          filter = path: type: let
            r = attrs.filter path type;
          in
            builtins.trace "${attrs.name}.filter ${path} = ${boolToString r}" r;
        }
      )
      // {
        satisfiesSubpathInvariant = src ? satisfiesSubpathInvariant && src.satisfiesSubpathInvariant;
      };

  /*
   Filter sources by a list of regular expressions.
   
   Example: 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
   source directory or its descendants, omitting files that do not match
   any suffix. The result of the example below will include files like
   `./dir/module.c` and `./dir/subdir/doc.xml` if present.
   
   Type: sourceLike -> [String] -> Source
   
   Example:
     sourceFilesBySuffices ./. [ ".xml" ".c" ]
   */
  sourceFilesBySuffices =
    # Path or source containing the files to be returned
    src:
    # A list of file suffix strings
    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;};

  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 "${gitDir}/commondir"
            else gitDir;
          commonDir' = lib.removeSuffix "/" commonDir'';
          commonDir = absolutePath gitDir commonDir';
          refFile = lib.removePrefix "${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));

  # -------------------------------------------------------------------------- #
  # Internal functions
  #

  # toSourceAttributes : sourceLike -> SourceAttrs
  #
  # Convert any source-like object into a simple, singular representation.
  # We don't expose this representation in order to avoid having a fifth path-
  # like class of objects in the wild.
  # (Existing ones being: paths, strings, sources and x//{outPath})
  # So instead of exposing internals, we build a library of combinator functions.
  toSourceAttributes = src: let
    isFiltered = src ? _isLibCleanSourceWith;
  in {
    # The original path
    origSrc =
      if isFiltered
      then src.origSrc
      else src;
    filter =
      if isFiltered
      then src.filter
      else _: _: true;
    name =
      if isFiltered
      then src.name
      else "source";
  };

  # fromSourceAttributes : SourceAttrs -> Source
  #
  # Inverse of toSourceAttributes for Source objects.
  fromSourceAttributes = {
    origSrc,
    filter,
    name,
  }: {
    _isLibCleanSourceWith = true;
    inherit origSrc filter name;
    outPath = builtins.path {
      inherit filter name;
      path = origSrc;
    };
  };
in {
  inherit
    pathType
    pathIsDirectory
    pathIsRegularFile
    pathIsGitRepo
    commitIdFromGitRepo
    cleanSource
    cleanSourceWith
    cleanSourceFilter
    pathHasContext
    canCleanSource
    sourceByRegex
    sourceFilesBySuffices
    trace
    ;
}