"""Configuration manager for Zynq Flasher GUI.

Handles loading and saving YAML configuration files.
All paths are stored relative to the config file's directory.
"""

from __future__ import annotations

import os
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any

import yaml


DEFAULT_CONFIG: dict[str, Any] = {
    "xilinx_path": "",
    "zynq_ip": "192.168.100.11",
    "zynq_part": "XC7Z100",
    "tftp_upload_name": "z7bin",
    "serial_port": "",
    "serial_baudrate": 115200,
    "bootloader_bit_path": "",
    "bootloader_elf_path": "",
    "bootloader_bin_path": "",
    "fsbl_elf_path": "",
    "flash_type": "qspi-x4-single",
    "flash_model": "s25fl256s1",
    "erase_all": False,
    "firmware_bin_path": "",
    "reboot_timeout": 30,
    "ping_timeout": 5,
    "ping_count": 3,
    "uart_delay": 3,
    "inter_step_delay": 2,
    "boot_wait_delay": 10,
    "step_timeouts": {
        "check_env": 120,
        "flash_erase": 120,
        "flash_program": 600,
        "bitstream": 60,
        "elf_download": 60,
        "tftp_reboot": 120,
    },
}


@dataclass
class Config:
    """Application configuration loaded from a YAML file.

    All file paths are stored as relative paths from the config file's
    directory and resolved to absolute paths when accessed.
    """

    xilinx_path: str = ""
    zynq_ip: str = "192.168.100.11"
    zynq_part: str = "XC7Z100"
    tftp_upload_name: str = "z7bin"
    serial_port: str = ""
    serial_baudrate: int = 115200
    bootloader_bit_path: str = ""
    bootloader_elf_path: str = ""
    bootloader_bin_path: str = ""
    fsbl_elf_path: str = ""
    flash_type: str = "qspi-x4-single"
    flash_model: str = "s25fl256s1"
    erase_all: bool = False
    firmware_bin_path: str = ""
    reboot_timeout: int = 30
    ping_timeout: int = 5
    ping_count: int = 3
    uart_delay: int = 3
    inter_step_delay: int = 2
    boot_wait_delay: int = 10
    step_timeouts: dict[str, int] = field(default_factory=lambda: {})

    # Internal: path to the config file on disk
    _config_path: Path = field(default=None, init=False, repr=False)

    @classmethod
    def from_file(cls, path: str | Path) -> Config:
        """Load configuration from a YAML file.

        Args:
            path: Path to the YAML configuration file.

        Returns:
            A Config instance populated with values from the file.

        Raises:
            FileNotFoundError: If the config file does not exist.
            yaml.YAMLError: If the file contains invalid YAML.
        """
        config_path = Path(path).resolve()
        if not config_path.exists():
            raise FileNotFoundError(f"Config file not found: {config_path}")

        with open(config_path, "r", encoding="utf-8") as f:
            data = yaml.safe_load(f) or {}

        config = cls()
        config._config_path = config_path
        config._apply_data(data)
        return config

    @classmethod
    def from_default(cls) -> Config:
        """Create a Config with default values (no file path).

        Returns:
            A Config instance with default values.
        """
        return cls()

    @classmethod
    def create_default(cls, path: str | Path) -> Config:
        """Create a default config file and return a Config instance.

        Args:
            path: Where to write the default config file.

        Returns:
            A Config instance loaded from the newly created file.
        """
        config_path = Path(path).resolve()
        config_path.parent.mkdir(parents=True, exist_ok=True)

        with open(config_path, "w", encoding="utf-8") as f:
            yaml.dump(DEFAULT_CONFIG, f, default_flow_style=False)

        return cls.from_file(config_path)

    def _apply_data(self, data: dict[str, Any]) -> None:
        """Apply configuration data from a dictionary.

        Args:
            data: Dictionary of configuration key-value pairs.
        """
        for key, value in data.items():
            if hasattr(self, key):
                setattr(self, key, value)

    def save(self) -> None:
        """Save the current configuration to the YAML file.

        Resolves all paths to be relative to the config file's directory.

        Raises:
            RuntimeError: If no config file path is set.
        """
        if self._config_path is None:
            raise RuntimeError("No config file path set; use from_file() or create_default()")

        data = self._to_dict()
        with open(self._config_path, "w", encoding="utf-8") as f:
            yaml.dump(data, f, default_flow_style=False)

    def _to_dict(self) -> dict[str, Any]:
        """Convert configuration to a dictionary with relative paths.

        Returns:
            Dictionary representation of the config.
        """
        data = {
            "xilinx_path": self.xilinx_path,
            "zynq_ip": self.zynq_ip,
            "tftp_upload_name": self.tftp_upload_name,
            "serial_port": self.serial_port,
            "serial_baudrate": self.serial_baudrate,
            "bootloader_bit_path": self._relative_path(self.bootloader_bit_path),
            "bootloader_elf_path": self._relative_path(self.bootloader_elf_path),
            "bootloader_bin_path": self._relative_path(self.bootloader_bin_path),
            "fsbl_elf_path": self._relative_path(self.fsbl_elf_path),
            "flash_type": self.flash_type,
            "flash_model": self.flash_model,
            "erase_all": self.erase_all,
            "firmware_bin_path": self._relative_path(self.firmware_bin_path),
            "reboot_timeout": self.reboot_timeout,
            "ping_timeout": self.ping_timeout,
            "ping_count": self.ping_count,
            "uart_delay": self.uart_delay,
            "inter_step_delay": self.inter_step_delay,
            "boot_wait_delay": self.boot_wait_delay,
            "step_timeouts": self.step_timeouts,
        }
        return data

    def _relative_path(self, path: str) -> str:
        """Convert an absolute path to a relative path from the config file.

        Args:
            path: Absolute path string.

        Returns:
            Relative path string, or the original if conversion fails.
        """
        if not path:
            return ""
        try:
            target = Path(path)
            if target.is_absolute():
                return str(target.relative_to(self._config_path.parent))
        except (ValueError, OSError):
            pass
        return path

    def resolve_path(self, relative_path: str) -> Path:
        """Resolve a relative config path to an absolute path.

        Args:
            relative_path: Path relative to the config file's directory.

        Returns:
            Absolute Path object.
        """
        if not relative_path:
            return Path()
        return (self._config_path.parent / relative_path).resolve()

    @property
    def config_path(self) -> Path | None:
        """Return the path to the config file on disk."""
        return self._config_path