"""
Unit tests for Pipeline orchestration framework.

Tests cover:
- Stage execution in sequence
- Result caching and retrieval
- Exception handling
- State reset functionality
"""

import pytest
from typing import Any

from src.pipeline.pipeline import (
    Stage,
    PipelineExecutor,
    LambdaStage,
    StageResult,
)


class AddStage(Stage):
    """Test stage that adds a value."""

    def __init__(self, name: str, value: int):
        super().__init__(name)
        self.value = value

    def execute(self, input_data: int) -> int:
        return input_data + self.value


class MultiplyStage(Stage):
    """Test stage that multiplies by a value."""

    def __init__(self, name: str, value: int):
        super().__init__(name)
        self.value = value

    def execute(self, input_data: int) -> int:
        return input_data * self.value


class FailingStage(Stage):
    """Test stage that always raises an exception."""

    def __init__(self, name: str, error_message: str = "Stage failed"):
        super().__init__(name)
        self.error_message = error_message

    def execute(self, input_data: Any) -> Any:
        raise RuntimeError(self.error_message)


class IdentityStage(Stage):
    """Test stage that returns input unchanged."""

    def execute(self, input_data: Any) -> Any:
        return input_data


class TestStage:
    """Test cases for Stage base class."""

    def test_stage_has_name(self):
        """Test that stage stores its name."""
        stage = AddStage("add_ten", 10)
        assert stage.name == "add_ten"

    def test_stage_repr(self):
        """Test stage string representation."""
        stage = AddStage("add_ten", 10)
        assert "AddStage" in repr(stage)
        assert "add_ten" in repr(stage)

    def test_subclass_must_implement_execute(self):
        """Test that Stage subclasses must implement execute."""
        # With abc.ABC, TypeError is raised at instantiation time
        with pytest.raises(TypeError, match="abstract"):
            Stage("test")  # type: ignore


class TestLambdaStage:
    """Test cases for LambdaStage convenience class."""

    def test_lambda_stage_executes_function(self):
        """Test that LambdaStage wraps and executes a function."""
        stage = LambdaStage("double", lambda x: x * 2)
        assert stage.execute(5) == 10

    def test_lambda_stage_with_string_function(self):
        """Test LambdaStage with string manipulation."""
        stage = LambdaStage("uppercase", lambda s: s.upper())
        assert stage.execute("hello") == "HELLO"


class TestPipelineExecutorCreation:
    """Test cases for PipelineExecutor creation and configuration."""

    def test_create_pipeline(self):
        """Test creating a new pipeline."""
        pipeline = PipelineExecutor("TestPipeline")
        assert pipeline.name == "TestPipeline"
        assert len(pipeline) == 0

    def test_add_stage(self):
        """Test adding a stage to the pipeline."""
        pipeline = PipelineExecutor()
        stage = AddStage("add_ten", 10)
        result = pipeline.add_stage(stage)

        assert len(pipeline) == 1
        assert result is pipeline  # Method chaining

    def test_add_multiple_stages(self):
        """Test adding multiple stages."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        assert len(pipeline) == 2

    def test_add_stage_raises_for_non_stage(self):
        """Test that adding non-Stage objects raises TypeError."""
        pipeline = PipelineExecutor()

        with pytest.raises(TypeError):
            pipeline.add_stage("not a stage")  # type: ignore

    def test_get_stage_names(self):
        """Test getting list of stage names."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        names = pipeline.get_stage_names()
        assert names == ["add_ten", "double"]

    def test_clear_stages(self):
        """Test clearing all stages."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.clear_stages()

        assert len(pipeline) == 0


class TestPipelineExecutorSequentialExecution:
    """Test cases for sequential stage execution."""

    def test_execute_single_stage(self):
        """Test executing a single stage."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))

        result = pipeline.execute(5)
        assert result == 15

    def test_execute_multiple_stages_in_order(self):
        """Test that stages execute in the correct order."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        # (5 + 10) * 2 = 30
        result = pipeline.execute(5)
        assert result == 30

    def test_execute_complex_pipeline(self):
        """Test a more complex multi-stage pipeline."""
        pipeline = PipelineExecutor("Complex")
        pipeline.add_stage(AddStage("add_five", 5))
        pipeline.add_stage(MultiplyStage("triple", 3))
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("halve", 0.5))

        # ((5 + 5) * 3 + 10) * 0.5 = (10 * 3 + 10) * 0.5 = 40 * 0.5 = 20
        result = pipeline.execute(5)
        assert result == 20.0

    def test_execute_with_string_data(self):
        """Test pipeline with string data transformation."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(LambdaStage("prefix", lambda s: ">> " + s))
        pipeline.add_stage(LambdaStage("suffix", lambda s: s + " <<"))

        result = pipeline.execute("hello")
        assert result == ">> hello <<"

    def test_execute_with_list_data(self):
        """Test pipeline with list data transformation."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(LambdaStage("append", lambda lst: lst + [3]))
        pipeline.add_stage(LambdaStage("extend", lambda lst: lst + [4, 5]))

        result = pipeline.execute([1, 2])
        assert result == [1, 2, 3, 4, 5]

    def test_execute_empty_pipeline_raises(self):
        """Test that executing an empty pipeline raises ValueError."""
        pipeline = PipelineExecutor()

        with pytest.raises(ValueError, match="no stages"):
            pipeline.execute(10)


class TestPipelineStageResultCaching:
    """Test cases for stage result caching and retrieval."""

    def test_get_stage_result(self):
        """Test retrieving a specific stage result."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        pipeline.execute(5)

        result = pipeline.get_stage_result("add_ten")
        assert result is not None
        assert result.stage_name == "add_ten"
        assert result.success is True
        assert result.output == 15

    def test_get_stage_result_for_nonexistent_stage(self):
        """Test getting result for non-existent stage."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.execute(5)

        result = pipeline.get_stage_result("nonexistent")
        assert result is None

    def test_get_all_results(self):
        """Test getting all stage results."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        pipeline.execute(5)

        results = pipeline.get_all_results()
        assert len(results) == 2
        assert "add_ten" in results
        assert "double" in results

    def test_get_final_output(self):
        """Test getting the final pipeline output."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        pipeline.execute(5)

        output = pipeline.get_final_output()
        assert output == 30

    def test_intermediate_stage_outputs(self):
        """Test that intermediate stage outputs are correct."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_five", 5))
        pipeline.add_stage(MultiplyStage("triple", 3))
        pipeline.add_stage(AddStage("add_ten", 10))

        pipeline.execute(5)

        # Input: 5
        # add_five: 5 + 5 = 10
        # triple: 10 * 3 = 30
        # add_ten: 30 + 10 = 40
        assert pipeline.get_stage_result("add_five").output == 10
        assert pipeline.get_stage_result("triple").output == 30
        assert pipeline.get_stage_result("add_ten").output == 40


class TestPipelineExceptionHandling:
    """Test cases for exception handling during execution."""

    def test_exception_stops_execution(self):
        """Test that an exception stops further stage execution."""
        executed_count = [0]

        class CountingStage(Stage):
            def execute(self, input_data):
                executed_count[0] += 1
                return input_data

        pipeline = PipelineExecutor()
        pipeline.add_stage(CountingStage("first"))
        pipeline.add_stage(FailingStage("fails"))
        pipeline.add_stage(CountingStage("never_runs"))

        pipeline.execute(10)

        # Only first stage and failing stage should have run
        assert executed_count[0] == 1

    def test_exception_is_caught(self):
        """Test that exceptions are caught and stored."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails", "Custom error"))
        pipeline.add_stage(MultiplyStage("double", 2))

        result = pipeline.execute(5)

        assert result is None  # Returns None on failure

    def test_get_last_exception(self):
        """Test retrieving the last exception."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails", "Test error"))

        pipeline.execute(5)

        exception = pipeline.get_last_exception()
        assert exception is not None
        assert isinstance(exception, RuntimeError)
        assert "Test error" in str(exception)

    def test_get_stopped_at_stage(self):
        """Test getting the stage where execution stopped."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails"))
        pipeline.add_stage(MultiplyStage("double", 2))

        pipeline.execute(5)

        stopped_at = pipeline.get_stopped_at_stage()
        assert stopped_at == "fails"

    def test_failed_stage_result(self):
        """Test that failed stage result has correct info."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails"))

        pipeline.execute(5)

        result = pipeline.get_stage_result("fails")
        assert result.success is False
        assert result.error is not None
        assert isinstance(result.error, RuntimeError)

    def test_is_completed_returns_false_on_failure(self):
        """Test that is_completed returns False after failure."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails"))

        pipeline.execute(5)

        assert pipeline.is_completed() is False

    def test_is_completed_returns_true_on_success(self):
        """Test that is_completed returns True after success."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))

        pipeline.execute(5)

        assert pipeline.is_completed() is True

    def test_first_stage_failure(self):
        """Test handling of failure in the first stage."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(FailingStage("first_fails"))
        pipeline.add_stage(AddStage("add_ten", 10))

        pipeline.execute(5)

        assert pipeline.get_stopped_at_stage() == "first_fails"
        assert pipeline.get_stage_result("add_ten") is None


class TestPipelineReset:
    """Test cases for pipeline state reset functionality."""

    def test_reset_clears_results(self):
        """Test that reset clears cached results."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        pipeline.execute(5)
        assert pipeline.get_all_results()

        pipeline.reset()
        assert not pipeline.get_all_results()

    def test_reset_clears_exception(self):
        """Test that reset clears exception state."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(FailingStage("fails"))

        pipeline.execute(5)
        assert pipeline.get_last_exception() is not None

        pipeline.reset()
        assert pipeline.get_last_exception() is None

    def test_reset_clears_stopped_at(self):
        """Test that reset clears stopped_at_stage."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(FailingStage("fails"))

        pipeline.execute(5)
        assert pipeline.get_stopped_at_stage() is not None

        pipeline.reset()
        assert pipeline.get_stopped_at_stage() is None

    def test_re_execute_after_reset(self):
        """Test that pipeline can be re-executed after reset."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))

        pipeline.execute(5)
        assert pipeline.get_final_output() == 15

        pipeline.reset()
        pipeline.execute(20)
        assert pipeline.get_final_output() == 30

    def test_re_execute_after_failure_and_reset(self):
        """Test re-execution after failure and reset."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(FailingStage("fails"))

        pipeline.execute(5)
        assert pipeline.is_completed() is False

        # Fix the pipeline by replacing the failing stage
        pipeline.reset()
        pipeline._stages = [pipeline._stages[0], MultiplyStage("double", 2)]

        pipeline.execute(5)
        assert pipeline.is_completed() is True
        assert pipeline.get_final_output() == 30


class TestPipelineRepr:
    """Test cases for string representations."""

    def test_pipeline_repr(self):
        """Test pipeline string representation."""
        pipeline = PipelineExecutor("TestPipeline")
        pipeline.add_stage(AddStage("add_ten", 10))
        pipeline.add_stage(MultiplyStage("double", 2))

        repr_str = repr(pipeline)
        assert "TestPipeline" in repr_str
        assert "2" in repr_str  # Stage count

    def test_stage_result_repr_success(self):
        """Test StageResult repr for success."""
        result = StageResult("test_stage", success=True, output=42)
        assert "test_stage" in repr(result)
        assert "success=True" in repr(result)

    def test_stage_result_repr_failure(self):
        """Test StageResult repr for failure."""
        error = RuntimeError("test error")
        result = StageResult("test_stage", success=False, error=error)
        assert "test_stage" in repr(result)
        assert "success=False" in repr(result)


class TestPipelineWithVariousDataTypes:
    """Test pipeline behavior with different data types."""

    def test_pipeline_with_dict(self):
        """Test pipeline transforming dictionaries."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(LambdaStage("add_key", lambda d: {**d, "y": 20}))
        pipeline.add_stage(LambdaStage("add_another", lambda d: {**d, "z": 30}))

        result = pipeline.execute({"x": 10})
        assert result == {"x": 10, "y": 20, "z": 30}

    def test_pipeline_with_identity_stages(self):
        """Test pipeline with stages that pass data through unchanged."""
        pipeline = PipelineExecutor()
        pipeline.add_stage(IdentityStage("first"))
        pipeline.add_stage(IdentityStage("second"))
        pipeline.add_stage(IdentityStage("third"))

        test_data = {"complex": "object"}
        result = pipeline.execute(test_data)

        assert result is test_data
        assert pipeline.is_completed() is True