import python
private import semmle.python.objects.TObject
private import semmle.python.objects.ObjectInternal
private import semmle.python.pointsto.PointsTo
private import semmle.python.pointsto.PointsToContext
private import semmle.python.pointsto.MRO
private import semmle.python.types.Builtins

abstract class SequenceObjectInternal extends ObjectInternal {
  /** Gets the `n`th item of this sequence, if one exists. */
  abstract ObjectInternal getItem(int n);

  override boolean booleanValue() {
    this.length() = 0 and result = false
    or
    this.length() != 0 and result = true
  }

  override boolean isDescriptor() { result = false }

  pragma[noinline]
  override predicate descriptorGetClass(ObjectInternal cls, ObjectInternal value, CfgOrigin origin) {
    none()
  }

  pragma[noinline]
  override predicate descriptorGetInstance(
    ObjectInternal instance, ObjectInternal value, CfgOrigin origin
  ) {
    none()
  }

  pragma[noinline]
  override predicate binds(ObjectInternal instance, string name, ObjectInternal descriptor) {
    none()
  }

  override string getName() { none() }

  override predicate contextSensitiveCallee() { none() }

  override ObjectInternal getIterNext() { result = this.getItem(_) }
}

abstract class TupleObjectInternal extends SequenceObjectInternal {
  override string toString() { result = "(" + this.contents(0) + ")" }

  private string contents(int n) {
    n < 4 and n = this.length() and result = ""
    or
    n = 3 and this.length() > 3 and result = (this.length() - 3).toString() + " more..."
    or
    result = this.item(n) + ", " + this.contents(n + 1)
  }

  private string item(int n) {
    result = bounded_toString(this.getItem(n))
    or
    n in [0 .. this.length() - 1] and
    not exists(this.getItem(n)) and
    result = "?"
  }

  /** Gets the class declaration for this object, if it is a declared class. */
  override ClassDecl getClassDeclaration() { none() }

  /** True if this "object" is a class. */
  override boolean isClass() { result = false }

  override ObjectInternal getClass() { result = ObjectInternal::builtin("tuple") }

  /**
   * True if this "object" can be meaningfully analyzed for
   * truth or false in comparisons. For example, `None` or `int` can be, but `int()`
   * or an unknown string cannot.
   */
  override predicate notTestableForEquality() { none() }

  /**
   * Holds if `obj` is the result of calling `this` and `origin` is
   * the origin of `obj`.
   */
  override predicate callResult(ObjectInternal obj, CfgOrigin origin) { none() }

  /**
   * Holds if `obj` is the result of calling `this` and `origin` is
   * the origin of `obj` with callee context `callee`.
   */
  override predicate callResult(PointsToContext callee, ObjectInternal obj, CfgOrigin origin) {
    none()
  }

  override int intValue() { none() }

  override string strValue() { none() }

  override predicate calleeAndOffset(Function scope, int paramOffset) { none() }

  pragma[noinline]
  override predicate attribute(string name, ObjectInternal value, CfgOrigin origin) { none() }

  pragma[noinline]
  override predicate attributesUnknown() { none() }

  override predicate subscriptUnknown() { none() }
}

/** A tuple built-in to the interpreter, including the empty tuple. */
class BuiltinTupleObjectInternal extends TBuiltinTuple, TupleObjectInternal {
  override predicate introducedAt(ControlFlowNode node, PointsToContext context) { none() }

  override Builtin getBuiltin() { this = TBuiltinTuple(result) }

  override ControlFlowNode getOrigin() { none() }

  override ObjectInternal getItem(int n) { result.getBuiltin() = this.getBuiltin().getItem(n) }

  override int length() {
    exists(Builtin b |
      b = this.getBuiltin() and
      result = count(int n | exists(b.getItem(n)))
    )
  }

  override predicate useOriginAsLegacyObject() { none() }

  override predicate isNotSubscriptedType() { any() }
}

/** A tuple declared by a tuple expression in the Python source code */
class PythonTupleObjectInternal extends TPythonTuple, TupleObjectInternal {
  override predicate introducedAt(ControlFlowNode node, PointsToContext context) {
    this = TPythonTuple(node, context)
  }

  override Builtin getBuiltin() { none() }

  override ControlFlowNode getOrigin() { this = TPythonTuple(result, _) }

  override ObjectInternal getItem(int n) {
    exists(TupleNode t, PointsToContext context |
      this = TPythonTuple(t, context) and
      PointsToInternal::pointsTo(t.getElement(n), context, result, _)
    )
  }

  override int length() {
    exists(TupleNode t |
      this = TPythonTuple(t, _) and
      result = count(int n | exists(t.getElement(n)))
    )
  }

  override predicate useOriginAsLegacyObject() { none() }

  override predicate isNotSubscriptedType() { any() }
}

/** A tuple created by a `*` parameter */
class VarargsTupleObjectInternal extends TVarargsTuple, TupleObjectInternal {
  override predicate introducedAt(ControlFlowNode node, PointsToContext context) { none() }

  override Builtin getBuiltin() { none() }

  override ControlFlowNode getOrigin() { none() }

  override ObjectInternal getItem(int n) {
    exists(CallNode call, PointsToContext context, int offset, int length |
      this = TVarargsTuple(call, context, offset, length) and
      n < length and
      InterProceduralPointsTo::positional_argument_points_to(call, offset + n, context, result, _)
    )
  }

  override int length() { this = TVarargsTuple(_, _, _, result) }

  override predicate useOriginAsLegacyObject() { any() }

  override predicate isNotSubscriptedType() { any() }
}

/**
 * The `sys.version_info` object. We treat this specially to prevent premature pruning and
 * false positives when we are unsure of the actual version of Python that the code is expecting.
 */
class SysVersionInfoObjectInternal extends TSysVersionInfo, SequenceObjectInternal {
  override string toString() { result = "sys.version_info" }

  override ObjectInternal getItem(int n) {
    n = 0 and result = TInt(major_version())
    or
    n = 1 and result = TInt(minor_version())
  }

  override predicate introducedAt(ControlFlowNode node, PointsToContext context) { none() }

  /** Gets the class declaration for this object, if it is a declared class. */
  override ClassDecl getClassDeclaration() {
    result = Builtin::special("sys").getMember("version_info").getClass()
  }

  /** True if this "object" is a class. */
  override boolean isClass() { result = false }

  override ObjectInternal getClass() { result.getBuiltin() = this.getClassDeclaration() }

  override predicate notTestableForEquality() { none() }

  /**
   * Gets the `Builtin` for this object, if any.
   * Objects (except unknown and undefined values) should attempt to return
   * exactly one result for either this method or `getOrigin()`.
   */
  override Builtin getBuiltin() { none() }

  /**
   * Gets a control flow node that represents the source origin of this
   * objects.
   */
  override ControlFlowNode getOrigin() { none() }

  /**
   * Holds if `obj` is the result of calling `this` and `origin` is
   * the origin of `obj`.
   */
  override predicate callResult(ObjectInternal obj, CfgOrigin origin) { none() }

  /**
   * Holds if `obj` is the result of calling `this` and `origin` is
   * the origin of `obj` with callee context `callee`.
   */
  override predicate callResult(PointsToContext callee, ObjectInternal obj, CfgOrigin origin) {
    none()
  }

  override int intValue() { none() }

  override string strValue() { none() }

  override predicate calleeAndOffset(Function scope, int paramOffset) { none() }

  override predicate attribute(string name, ObjectInternal value, CfgOrigin origin) { none() }

  override predicate attributesUnknown() { none() }

  override predicate subscriptUnknown() { none() }

  override int length() { result = 5 }

  override predicate functionAndOffset(CallableObjectInternal function, int offset) { none() }

  override predicate useOriginAsLegacyObject() { any() }

  override predicate isNotSubscriptedType() { any() }
}