"""Tool execution engine."""

import argparse
import sys
from pathlib import Path
from typing import Optional

from .tool import load_tool, Tool, PromptStep, CodeStep
from .providers import call_provider, mock_provider


def substitute_variables(template: str, variables: dict) -> str:
    """
    Substitute {variable} placeholders in a template.

    Args:
        template: String with {var} placeholders
        variables: Dict of variable name -> value

    Returns:
        String with placeholders replaced
    """
    result = template
    for name, value in variables.items():
        result = result.replace(f"{{{name}}}", str(value) if value else "")
    return result


def execute_prompt_step(step: PromptStep, variables: dict, provider_override: str = None) -> tuple[str, bool]:
    """
    Execute a prompt step.

    Args:
        step: The prompt step to execute
        variables: Current variable values
        provider_override: Override the step's provider

    Returns:
        Tuple of (output_value, success)
    """
    # Build prompt with variable substitution
    prompt = substitute_variables(step.prompt, variables)

    # Call provider
    provider = provider_override or step.provider

    if provider.lower() == "mock":
        result = mock_provider(prompt)
    else:
        result = call_provider(provider, prompt)

    if not result.success:
        print(f"Error in prompt step: {result.error}", file=sys.stderr)
        return "", False

    return result.text, True


def execute_code_step(step: CodeStep, variables: dict) -> tuple[dict, bool]:
    """
    Execute a code step.

    Args:
        step: The code step to execute
        variables: Current variable values (available in code)

    Returns:
        Tuple of (output_vars_dict, success)
    """
    # Substitute variables in code (like {outputfile} -> actual value)
    code = substitute_variables(step.code, variables)

    # Create execution environment with variables
    local_vars = dict(variables)

    try:
        # Execute the code with substituted variables
        exec(code, {"__builtins__": __builtins__}, local_vars)

        # Support comma-separated output vars (e.g., "a, b, c")
        output_vars = [v.strip() for v in step.output_var.split(',')]
        outputs = {}
        for var in output_vars:
            outputs[var] = str(local_vars.get(var, ""))

        return outputs, True

    except Exception as e:
        print(f"Error in code step: {e}", file=sys.stderr)
        return {}, False


def run_tool(
    tool: Tool,
    input_text: str,
    custom_args: dict,
    provider_override: Optional[str] = None,
    dry_run: bool = False,
    show_prompt: bool = False,
    verbose: bool = False
) -> tuple[str, int]:
    """
    Execute a tool.

    Args:
        tool: Tool definition
        input_text: Input content
        custom_args: Custom argument values
        provider_override: Override all providers
        dry_run: Just show what would happen
        show_prompt: Show prompts in addition to output
        verbose: Show debug info

    Returns:
        Tuple of (output_text, exit_code)
    """
    # Initialize variables with input and arguments
    variables = {"input": input_text}

    # Add argument values (with defaults)
    for arg in tool.arguments:
        value = custom_args.get(arg.variable, arg.default)
        variables[arg.variable] = value

    if verbose:
        print(f"[verbose] Tool: {tool.name}", file=sys.stderr)
        print(f"[verbose] Variables: {list(variables.keys())}", file=sys.stderr)
        print(f"[verbose] Steps: {len(tool.steps)}", file=sys.stderr)

    # If no steps, just substitute output template
    if not tool.steps:
        output = substitute_variables(tool.output, variables)
        return output, 0

    # Execute each step
    for i, step in enumerate(tool.steps):
        if verbose:
            step_type = "PROMPT" if isinstance(step, PromptStep) else "CODE"
            print(f"[verbose] Step {i+1}: {step_type} -> {{{step.output_var}}}", file=sys.stderr)

        if isinstance(step, PromptStep):
            # Show prompt if requested
            if show_prompt or dry_run:
                prompt = substitute_variables(step.prompt, variables)
                print(f"=== PROMPT (Step {i+1}, provider={step.provider}) ===", file=sys.stderr)
                print(prompt, file=sys.stderr)
                print("=== END PROMPT ===", file=sys.stderr)

            if dry_run:
                variables[step.output_var] = f"[DRY RUN - would call {step.provider}]"
            else:
                output, success = execute_prompt_step(step, variables, provider_override)
                if not success:
                    return "", 2
                variables[step.output_var] = output

        elif isinstance(step, CodeStep):
            if verbose or dry_run:
                print(f"=== CODE (Step {i+1}) -> {{{step.output_var}}} ===", file=sys.stderr)
                print(step.code, file=sys.stderr)
                print("=== END CODE ===", file=sys.stderr)

            if dry_run:
                # Handle comma-separated output vars for dry run
                for var in [v.strip() for v in step.output_var.split(',')]:
                    variables[var] = "[DRY RUN - would execute code]"
            else:
                outputs, success = execute_code_step(step, variables)
                if not success:
                    return "", 1
                # Merge all output vars into variables
                variables.update(outputs)

    # Generate final output
    output = substitute_variables(tool.output, variables)

    return output, 0


def create_argument_parser(tool: Tool) -> argparse.ArgumentParser:
    """
    Create an argument parser for a tool.

    Args:
        tool: Tool definition

    Returns:
        Configured ArgumentParser
    """
    parser = argparse.ArgumentParser(
        prog=tool.name,
        description=tool.description or f"SmartTools: {tool.name}"
    )

    # Universal flags
    parser.add_argument("-i", "--input", dest="input_file",
                        help="Input file (reads from stdin if piped)")
    parser.add_argument("--stdin", action="store_true",
                        help="Read input interactively from stdin (type then Ctrl+D)")
    parser.add_argument("-o", "--output", dest="output_file",
                        help="Output file (writes to stdout if omitted)")
    parser.add_argument("--dry-run", action="store_true",
                        help="Show what would happen without executing")
    parser.add_argument("--show-prompt", action="store_true",
                        help="Show prompts in addition to output")
    parser.add_argument("-p", "--provider",
                        help="Override provider (e.g., --provider mock)")
    parser.add_argument("-v", "--verbose", action="store_true",
                        help="Show debug information")

    # Tool-specific flags from arguments
    for arg in tool.arguments:
        parser.add_argument(
            arg.flag,
            dest=arg.variable,
            default=arg.default,
            help=arg.description or f"{arg.variable} (default: {arg.default})"
        )

    return parser


def main():
    """Entry point for tool execution via wrapper script."""
    if len(sys.argv) < 2:
        print("Usage: python -m smarttools.runner <tool_name> [args...]", file=sys.stderr)
        sys.exit(1)

    tool_name = sys.argv[1]
    tool = load_tool(tool_name)

    if tool is None:
        print(f"Error: Tool '{tool_name}' not found", file=sys.stderr)
        sys.exit(1)

    # Parse remaining arguments
    parser = create_argument_parser(tool)
    args = parser.parse_args(sys.argv[2:])

    # Read input
    if args.input_file:
        # Read from file
        input_path = Path(args.input_file)
        if not input_path.exists():
            print(f"Error: Input file not found: {args.input_file}", file=sys.stderr)
            sys.exit(1)
        input_text = input_path.read_text()
    elif args.stdin:
        # Explicit interactive input requested
        print("Reading from stdin (Ctrl+D to end):", file=sys.stderr)
        input_text = sys.stdin.read()
    elif not sys.stdin.isatty():
        # Stdin is piped - read it
        input_text = sys.stdin.read()
    else:
        # No input provided - use empty string
        input_text = ""

    # Collect custom args
    custom_args = {}
    for arg in tool.arguments:
        value = getattr(args, arg.variable, None)
        if value is not None:
            custom_args[arg.variable] = value

    # Run tool
    output, exit_code = run_tool(
        tool=tool,
        input_text=input_text,
        custom_args=custom_args,
        provider_override=args.provider,
        dry_run=args.dry_run,
        show_prompt=args.show_prompt,
        verbose=args.verbose
    )

    # Write output
    if exit_code == 0 and output:
        if args.output_file:
            Path(args.output_file).write_text(output)
        else:
            print(output)

    sys.exit(exit_code)


if __name__ == "__main__":
    main()