"""Role-aware preset transformation.

PresetTransformer decodes base64 preset data, modifies role-specific
parameters, and re-encodes. Each supported plugin has its own decoder.

For MVP: the transformer is a stub — role variants currently share
the same default preset data. Full parameter modification will be
implemented in a future iteration.
"""

from __future__ import annotations

import base64
import json
import re


class PresetTransformer:
    """Transforms plugin preset data for a specific track role.

    Each supported plugin has a decoder that base64-decodes preset chunks,
    a modifier that tweaks role-specific parameters, and re-encodes.

    For MVP: all transforms return the default chunks unchanged.
    """

    @staticmethod
    def derive(plugin: str, default_chunks: list[str], role: str) -> list[str]:
        """Derive role-specific preset data from default chunks.

        Args:
            plugin: PLUGIN_REGISTRY key (e.g. "Serum_2", "Decapitator")
            default_chunks: Base64 preset chunks for the \"default\" role.
            role: Track role string (e.g. "bass", "lead", "drums").

        Returns:
            Modified preset chunks for the given role. For MVP, returns
            default_chunks unchanged since full parameter modification
            is not yet implemented.
        """
        transformer = _TRANSFORMERS.get(plugin)
        if transformer is not None:
            return transformer(default_chunks, role)
        return list(default_chunks)


# ---------------------------------------------------------------------------
# Per-plugin transformers (MVP stubs)
# ---------------------------------------------------------------------------


def _transform_serum(chunks: list[str], role: str) -> list[str]:
    """Transform Serum_2 preset for a specific role.

    Serum preset format: base64 → JSON. The processor component has:
      - processor.osc.type  (0=sine, 1=saw, 2=square, 3=triangle)
      - processor.filter.cutoff (Hz, float)
      - processor.fx (bypass bits)

    For MVP: returns default chunks unchanged.
    Future: bass→sine+low_cutoff, lead→saw+open_filter.
    """
    return list(chunks)


def _transform_decapitator(chunks: list[str], role: str) -> list[str]:
    """Transform Decapitator preset for a specific role.

    Decapitator format: base64 → key=value text. Modifiable params:
      - Drive (float 0-1)
      - Tone (float 0-1)
      - Style (A-E letter)

    For MVP: returns default chunks unchanged.
    Future: drums→high_drive+A_style, bass→low_drive+E_style.
    """
    return list(chunks)


def _transform_omnisphere(chunks: list[str], role: str) -> list[str]:
    """Transform Omnisphere preset for a specific role.

    Omnisphere format: base64 → SynthMaster text block. Modifiable params:
      - Atk (attack time)
      - Dec (decay time)
      - Filter Freq

    For MVP: returns default chunks unchanged.
    Future: pad→slow_attack+filter_mod, chords→faster_attack.
    """
    return list(chunks)


# ---------------------------------------------------------------------------
# Registry
# ---------------------------------------------------------------------------

_TRANSFORMERS: dict[str, object] = {
    "Serum_2": _transform_serum,
    "Decapitator": _transform_decapitator,
    "Omnisphere": _transform_omnisphere,
}
