"""Tensor mapping and URL parsing utilities.

Provides utilities for mapping tensor names between different formats,
parsing model URLs, and handling architecture-specific conversions.
Uses UK English spelling conventions throughout.
"""

from __future__ import annotations

import re
from typing import ClassVar

from helpers.models.quantisation import ModelSource, URLType


class TensorMapper:
    """Maps tensor names between HuggingFace and GGUF conventions.

    Provides flexible tensor name translation supporting direct mappings,
    layer-aware transformations, and architecture-specific overrides.
    Handles both simple renames and complex pattern-based conversions.
    """

    # Common direct mappings across architectures
    DIRECT_MAPPINGS: ClassVar[dict[str, str]] = {
        "model.embed_tokens.weight": "token_embd.weight",
        "model.norm.weight": "output_norm.weight",
        "lm_head.weight": "output.weight",
    }

    # Layer component patterns for transformer blocks
    LAYER_PATTERNS: ClassVar[dict[str, str]] = {
        "self_attn.q_proj.weight": "attn_q.weight",
        "self_attn.q_proj.bias": "attn_q.bias",
        "self_attn.k_proj.weight": "attn_k.weight",
        "self_attn.k_proj.bias": "attn_k.bias",
        "self_attn.v_proj.weight": "attn_v.weight",
        "self_attn.v_proj.bias": "attn_v.bias",
        "self_attn.o_proj": "attn_output.weight",
        "mlp.gate_proj": "ffn_gate.weight",
        "mlp.up_proj": "ffn_up.weight",
        "mlp.down_proj": "ffn_down.weight",
        "input_layernorm": "attn_norm.weight",
        "post_attention_layernorm": "ffn_norm.weight",
    }

    @classmethod
    def map_tensor_name(cls, original_name: str) -> str | None:
        """Map original tensor name to GGUF format.

        Translates HuggingFace tensor naming to GGUF format, handling embeddings,
        attention layers, feed-forward networks, and normalisation layers. Uses
        layer-aware mapping for transformer blocks whilst maintaining consistency
        across different model architectures.

        Returns:
            GGUF tensor name, or None if unmappable.
        """
        # Check direct mappings first
        if original_name in cls.DIRECT_MAPPINGS:
            return cls.DIRECT_MAPPINGS[original_name]

        # Handle layer-specific tensors
        if ".layers." in original_name:
            return cls._map_layer_tensor(original_name)

        # Return None for unmapped tensors
        return None

    @classmethod
    def _map_layer_tensor(cls, tensor_name: str) -> str | None:
        """Map layer-specific tensor names.

        Handles tensors within transformer layers, extracting layer indices
        and mapping component names to GGUF conventions. Supports attention
        projections, feed-forward networks, and normalisation layers.

        Returns:
            Mapped GGUF tensor name with layer index, or None if unmappable.
        """
        # Extract layer number
        parts = tensor_name.split(".")
        layer_idx = None
        for i, part in enumerate(parts):
            if part == "layers" and i + 1 < len(parts):
                layer_idx = parts[i + 1]
                break

        if layer_idx is None:
            return None

        # Check each pattern
        for pattern, replacement in cls.LAYER_PATTERNS.items():
            if pattern in tensor_name:
                return f"blk.{layer_idx}.{replacement}"

        return None


class URLParser:
    """Parses and validates model URLs from various sources.

    Handles HuggingFace URLs, Ollama-style GGUF references, and other
    model source formats. Extracts metadata including author, model name,
    and file patterns for appropriate download strategies.
    """

    @staticmethod
    def parse(url: str) -> ModelSource:
        """Parse URL and extract model source information.

        Analyses URL format to determine source type and extract relevant
        metadata for model download and processing. Supports both standard
        HuggingFace URLs and Ollama-style GGUF repository references.

        Returns:
            ModelSource with parsed metadata and appropriate source type.

        Raises:
            ValueError: If URL format is not recognised or supported.
        """
        if not url:
            msg = "URL cannot be empty"
            raise ValueError(msg)

        # Try Ollama-style GGUF URL first (hf.co/author/model:pattern)
        ollama_match = re.match(r"^hf\.co/([^:]+):(.+)$", url)
        if ollama_match:
            source_model = ollama_match.group(1)
            gguf_pattern = ollama_match.group(2)
            return URLParser._create_model_source(
                url,
                URLType.OLLAMA_GGUF,
                source_model,
                gguf_file_pattern=gguf_pattern,
                is_gguf_repo=True,
            )

        # Try regular HuggingFace URL
        hf_match = re.match(r"https://huggingface\.co/([^/]+/[^/?]+)", url)
        if hf_match:
            source_model = hf_match.group(1)
            return URLParser._create_model_source(
                url, URLType.HUGGINGFACE, source_model, is_gguf_repo=False
            )

        msg = (
            "Invalid URL format\n"
            "Supported formats:\n"
            "  - https://huggingface.co/username/model-name\n"
            "  - hf.co/username/model-name-GGUF:F16"
        )
        raise ValueError(msg)

    @staticmethod
    def _create_model_source(
        url: str,
        url_type: URLType,
        source_model: str,
        gguf_file_pattern: str | None = None,
        is_gguf_repo: bool = False,
    ) -> ModelSource:
        """Create ModelSource with parsed information.

        Constructs a ModelSource instance with extracted metadata, handling
        author/model name splitting and GGUF suffix removal for repository names.
        Ensures consistent naming conventions across different source types.

        Returns:
            Configured ModelSource instance with normalised metadata.
        """
        author, model_name = source_model.split("/", 1)

        # Strip -GGUF suffix for GGUF repos
        if is_gguf_repo and model_name.endswith("-GGUF"):
            model_name = model_name[:-5]

        return ModelSource(
            url=url,
            url_type=url_type,
            source_model=source_model,
            original_author=author,
            model_name=model_name,
            gguf_file_pattern=gguf_file_pattern,
            is_gguf_repo=is_gguf_repo,
        )