path: root/pkgs/development/tools/poetry2nix/poetry2nix/pep508.nix

{ lib, stdenv }: python:

let

  # Like builtins.substring but with stop being offset instead of length
  substr = start: stop: s: builtins.substring start (stop - start) s;

  # Strip leading/trailing whitespace from string
  stripStr = s: lib.elemAt (builtins.split "^ *" (lib.elemAt (builtins.split " *$" s) 0)) 2;

  findSubExpressionsFun = acc: c: (
    if c == "(" then (
      let
        posNew = acc.pos + 1;
        isOpen = acc.openP == 0;
        startPos = if isOpen then posNew else acc.startPos;
      in
        acc // {
          inherit startPos;
          exprs = acc.exprs ++ [ (substr acc.exprPos (acc.pos - 1) acc.expr) ];
          pos = posNew;
          openP = acc.openP + 1;
        }
    ) else if c == ")" then (
      let
        openP = acc.openP - 1;
        exprs = findSubExpressions (substr acc.startPos acc.pos acc.expr);
      in
        acc // {
          inherit openP;
          pos = acc.pos + 1;
          exprs = if openP == 0 then acc.exprs ++ [ exprs ] else acc.exprs;
          exprPos = if openP == 0 then acc.pos + 1 else acc.exprPos;
        }
    ) else acc // { pos = acc.pos + 1; }
  );

  # Make a tree out of expression groups (parens)
  findSubExpressions = expr: let
    acc = builtins.foldl' findSubExpressionsFun {
      exprs = [];
      expr = expr;
      pos = 0;
      openP = 0;
      exprPos = 0;
      startPos = 0;
    } (lib.stringToCharacters expr);
    tailExpr = (substr acc.exprPos acc.pos expr);
    tailExprs = if tailExpr != "" then [ tailExpr ] else [];
  in
    acc.exprs ++ tailExprs;

  parseExpressions = exprs: let
    splitCond = (
      s: builtins.map
        (x: stripStr (if builtins.typeOf x == "list" then (builtins.elemAt x 0) else x))
        (builtins.split " (and|or) " (s + " "))
    );

    mapfn = expr: (
      if (builtins.match "^ ?$" expr != null) then null  # Filter empty
      else if (builtins.elem expr [ "and" "or" ]) then {
        type = "bool";
        value = expr;
      }
      else {
        type = "expr";
        value = expr;
      }
    );

    parse = expr: builtins.filter (x: x != null) (builtins.map mapfn (splitCond expr));

  in
    builtins.foldl' (
      acc: v: acc ++ (
        if builtins.typeOf v == "string" then parse v else [ (parseExpressions v) ]
      )
    ) [] exprs;

  # Transform individual expressions to structured expressions
  # This function also performs variable substitution, replacing environment markers with their explicit values
  transformExpressions = exprs: let
    variables = {
      os_name = "posix"; # TODO: Check other platforms
      sys_platform = (
        if stdenv.isLinux then "linux"
        else if stdenv.isDarwin then "darwin"
        else throw "Unsupported platform"
      );
      platform_machine = stdenv.platform.kernelArch;
      platform_python_implementation = "CPython"; # Only CPython supported for now
      platform_release = ""; # Field not reproducible
      platform_system = (
        if stdenv.isLinux then "Linux"
        else if stdenv.isDarwin then "Darwin"
        else throw "Unsupported platform"
      );
      platform_version = ""; # Field not reproducible
      python_version = python.passthru.pythonVersion;
      python_full_version = python.version;
      implementation_name = "cpython"; # Only cpython supported for now
      implementation_version = python.version;
      extra = "";
    };

    substituteVar = value: if builtins.hasAttr value variables then (builtins.toJSON variables."${value}") else value;

    processVar = value: builtins.foldl' (acc: v: v acc) value [
      stripStr
      substituteVar
    ];

  in
    if builtins.typeOf exprs == "set" then (
      if exprs.type == "expr" then (
        let
          mVal = ''[a-zA-Z0-9\'"_\. ]+'';
          mOp = "in|[!=<>]+";
          e = stripStr exprs.value;
          m = builtins.map stripStr (builtins.match ''^(${mVal}) *(${mOp}) *(${mVal})$'' e);
        in
          {
            type = "expr";
            value = {
              op = builtins.elemAt m 1;
              values = [
                (processVar (builtins.elemAt m 0))
                (processVar (builtins.elemAt m 2))
              ];
            };
          }
      ) else exprs
    ) else builtins.map transformExpressions exprs;

  # Recursively eval all expressions
  evalExpressions = exprs: let
    unmarshal = v: (
      # TODO: Handle single quoted values
      if v == "True" then true
      else if v == "False" then false
      else builtins.fromJSON v
    );
    hasElem = needle: haystack: builtins.elem needle (builtins.filter (x: builtins.typeOf x == "string") (builtins.split " " haystack));
    # TODO: Implement all operators
    op = {
      "<=" = x: y: (unmarshal x) <= (unmarshal y);
      "<" = x: y: (unmarshal x) < (unmarshal y);
      "!=" = x: y: x != y;
      "==" = x: y: x == y;
      ">=" = x: y: (unmarshal x) >= (unmarshal y);
      ">" = x: y: (unmarshal x) > (unmarshal y);
      "~=" = null;
      "===" = null;
      "in" = x: y: let
        values = builtins.filter (x: builtins.typeOf x == "string") (builtins.split " " (unmarshal y));
      in
        builtins.elem (unmarshal x) values;
    };
  in
    if builtins.typeOf exprs == "set" then (
      if exprs.type == "expr" then (
        let
          expr = exprs;
          result = (op."${expr.value.op}") (builtins.elemAt expr.value.values 0) (builtins.elemAt expr.value.values 1);
        in
          {
            type = "value";
            value = result;
          }
      ) else exprs
    ) else builtins.map evalExpressions exprs;

  # Now that we have performed an eval all that's left to do is to concat the graph into a single bool
  reduceExpressions = exprs: let
    cond = {
      "and" = x: y: x && y;
      "or" = x: y: x || y;
    };
    reduceExpressionsFun = acc: v: (
      if builtins.typeOf v == "set" then (
        if v.type == "value" then (
          acc // {
            value = cond."${acc.cond}" acc.value v.value;
          }
        ) else if v.type == "bool" then (
          acc // {
            cond = v.value;
          }
        ) else throw "Unsupported type"
      ) else if builtins.typeOf v == "list" then (
        let
          ret = builtins.foldl' reduceExpressionsFun {
            value = true;
            cond = "and";
          } v;
        in
          acc // {
            value = cond."${acc.cond}" acc.value ret.value;
          }
      ) else throw "Unsupported type"
    );
  in
    (
      builtins.foldl' reduceExpressionsFun {
        value = true;
        cond = "and";
      } exprs
    ).value;

in
e: builtins.foldl' (acc: v: v acc) e [
  findSubExpressions
  parseExpressions
  transformExpressions
  evalExpressions
  reduceExpressions
]