/**
 * @name Unresolved import
 * @description An unresolved import may result in reduced coverage and accuracy of analysis.
 * @kind problem
 * @problem.severity info
 * @id py/import-failure
 */

import python

ImportExpr alternative_import(ImportExpr ie) {
  exists(Alias thisalias, Alias otheralias |
    (thisalias.getValue() = ie or thisalias.getValue().(ImportMember).getModule() = ie) and
    (otheralias.getValue() = result or otheralias.getValue().(ImportMember).getModule() = result) and
    (
      exists(If i | i.getBody().contains(ie) and i.getOrelse().contains(result))
      or
      exists(If i | i.getBody().contains(result) and i.getOrelse().contains(ie))
      or
      exists(Try t | t.getBody().contains(ie) and t.getAHandler().contains(result))
      or
      exists(Try t | t.getBody().contains(result) and t.getAHandler().contains(ie))
    )
  )
}

string os_specific_import(ImportExpr ie) {
  exists(string name | name = ie.getImportedModuleName() |
    name.matches("org.python.%") and result = "java"
    or
    name.matches("java.%") and result = "java"
    or
    name.matches("Carbon.%") and result = "darwin"
    or
    result = "win32" and
    (
      name = "_winapi" or
      name = "_win32api" or
      name = "_winreg" or
      name = "nt" or
      name.matches("win32%") or
      name = "ntpath"
    )
    or
    result = "linux2" and
    (name = "posix" or name = "posixpath")
    or
    result = "unsupported" and
    (name = "__pypy__" or name = "ce" or name.matches("riscos%"))
  )
}

string get_os() { py_flags_versioned("sys.platform", result, major_version().toString()) }

predicate ok_to_fail(ImportExpr ie) {
  alternative_import(ie).refersTo(_)
  or
  os_specific_import(ie) != get_os()
}

class VersionTest extends ControlFlowNode {
  VersionTest() {
    exists(string name |
      name.matches("%version%") and
      this.(CompareNode).getAChild+().pointsTo(Module::named("sys").attr(name))
    )
  }

  override string toString() { result = "VersionTest" }
}

/** A guard on the version of the Python interpreter */
class VersionGuard extends ConditionBlock {
  VersionGuard() { this.getLastNode() instanceof VersionTest }
}

from ImportExpr ie
where
  not ie.refersTo(_) and
  exists(Context c | c.appliesTo(ie.getAFlowNode())) and
  not ok_to_fail(ie) and
  not exists(VersionGuard guard | guard.controls(ie.getAFlowNode().getBasicBlock(), _))
select ie, "Unable to resolve import of '" + ie.getImportedModuleName() + "'."