"""
Pipeline orchestrator for the conversion process.

This module implements the pipeline pattern, coordinating the execution
of multiple stages in sequence to convert inputs to LaTeX.
"""

import time
import logging
from typing import List, Optional
from .interfaces import Stage, ConversionContext

logger = logging.getLogger(__name__)


class ConversionPipeline:
    """
    Orchestrates conversion through multiple stages.

    The pipeline executes stages in sequence, passing the context from
    one stage to the next. Each stage can read from and write to the
    shared context object.

    Example:
        >>> pipeline = (ConversionPipeline()
        ...     .add_stage(InputStage())
        ...     .add_stage(ValidationStage())
        ...     .add_stage(ConversionStage())
        ...     .add_stage(OutputStage()))
        >>> context = ConversionContext(input_type='mathml', mathml='<math>...</math>')
        >>> result = pipeline.process(context)
    """

    def __init__(self, enable_validation: bool = True, enable_timing: bool = True):
        """
        Initialize the pipeline.

        Args:
            enable_validation: Whether to validate stage preconditions before execution
            enable_timing: Whether to record stage execution times
        """
        self.stages: List[Stage] = []
        self.enable_validation = enable_validation
        self.enable_timing = enable_timing

    def add_stage(self, stage: Stage) -> 'ConversionPipeline':
        """
        Add a stage to the pipeline (fluent interface).

        Args:
            stage: The stage to add to the pipeline

        Returns:
            Self for method chaining

        Raises:
            TypeError: If stage is not an instance of Stage
        """
        if not isinstance(stage, Stage):
            raise TypeError(f"Stage must be instance of Stage, got {type(stage)}")

        self.stages.append(stage)
        logger.debug(f"Added stage: {stage.name}")
        return self

    def process(self, context: ConversionContext) -> ConversionContext:
        """
        Execute all stages in order.

        Args:
            context: The initial conversion context

        Returns:
            Updated conversion context after all stages

        Raises:
            ValueError: If any stage validation fails
            RuntimeError: If any stage processing fails
        """
        if not self.stages:
            raise RuntimeError("Pipeline has no stages configured")

        logger.info(f"Starting pipeline with {len(self.stages)} stages")
        pipeline_start_time = time.time()

        try:
            for stage in self.stages:
                context = self._execute_stage(stage, context)

            # Record total pipeline time
            pipeline_end_time = time.time()
            context.total_time = pipeline_end_time - pipeline_start_time

            logger.info(
                f"Pipeline completed successfully in {context.total_time:.4f}s "
                f"({len(self.stages)} stages)"
            )
            return context

        except Exception as e:
            logger.error(f"Pipeline failed: {e}", exc_info=True)
            raise

    def _execute_stage(self, stage: Stage, context: ConversionContext) -> ConversionContext:
        """
        Execute a single stage with validation and timing.

        Args:
            stage: The stage to execute
            context: The current context

        Returns:
            Updated context after stage execution

        Raises:
            ValueError: If stage validation fails
            RuntimeError: If stage execution fails
        """
        logger.debug(f"Executing stage: {stage.name}")

        # Validate preconditions if enabled
        if self.enable_validation:
            if not stage.validate_input(context):
                error_msg = f"Stage '{stage.name}' validation failed"
                logger.error(error_msg)
                raise ValueError(error_msg)

        # Execute stage with timing
        if self.enable_timing:
            stage_start_time = time.time()
            context = stage.process(context)
            stage_end_time = time.time()
            stage_time = stage_end_time - stage_start_time
            context.record_stage_time(stage.name, stage_time)
            logger.debug(f"Stage '{stage.name}' completed in {stage_time:.4f}s")
        else:
            context = stage.process(context)

        return context

    def clear(self) -> 'ConversionPipeline':
        """
        Remove all stages from the pipeline.

        Returns:
            Self for method chaining
        """
        self.stages.clear()
        logger.debug("Pipeline cleared")
        return self

    def get_stages(self) -> List[Stage]:
        """Get a copy of the stages list."""
        return self.stages.copy()

    def get_stage_count(self) -> int:
        """Get the number of stages in the pipeline."""
        return len(self.stages)

    def __repr__(self) -> str:
        """String representation for debugging."""
        stage_names = [stage.name for stage in self.stages]
        return f"ConversionPipeline(stages={stage_names})"

    def __str__(self) -> str:
        """Human-readable representation."""
        if not self.stages:
            return "ConversionPipeline (empty)"

        stage_list = "\n  ".join([f"{i+1}. {stage.name}" for i, stage in enumerate(self.stages)])
        return f"ConversionPipeline ({len(self.stages)} stages):\n  {stage_list}"