from __future__ import annotations

# The following code is inspired from: https://github.com/ericcurtin/lm-pull/blob/main/lm-pull.py
import os
import shutil
import sys
import time
import urllib.request
from typing import Optional

import ramalama.console as console
from ramalama.common import perror
from ramalama.config import ActiveConfig
from ramalama.file import File
from ramalama.logger import logger
from ramalama.proxy_support import setup_proxy_support

# Setup proxy support on module import
setup_proxy_support()

HTTP_NOT_FOUND = 404
HTTP_RANGE_NOT_SATISFIABLE = 416  # "Range Not Satisfiable" error (file already downloaded)


class HttpClient:
    def __init__(self):
        pass

    def init(self, url, headers, output_file, show_progress, response_bytes=None):
        output_file_partial = None
        if output_file:
            output_file_partial = output_file + ".partial"

        self.file_size = self.set_resume_point(output_file_partial)
        self.urlopen(url, headers)
        self.total_to_download = int(self.response.getheader('content-length', 0))
        if response_bytes is not None:
            response_bytes.append(self.response.read())
        else:
            out = File()
            try:
                if not out.open(output_file_partial, "ab"):
                    raise IOError("Failed to open file")

                if out.lock():
                    raise IOError("Failed to exclusively lock file")

                self.now_downloaded = 0
                self.start_time = time.time()
                self.perform_download(out.file, show_progress)
            finally:
                del out  # Ensure file is closed before rename

        if output_file:
            if output_file_partial is None:
                raise RuntimeError(
                    "output_file is set but output_file_partial is None; temporary output file was never created"
                )
            os.rename(output_file_partial, output_file)

    def urlopen(self, url, headers):
        headers["Range"] = f"bytes={self.file_size}-"
        logger.debug(f"Running urlopen {url} with headers: {headers}")
        request = urllib.request.Request(url, headers=headers)
        self.response = urllib.request.urlopen(request)

        if self.response.status not in (200, 206):
            raise IOError(f"Request failed: {self.response.status}")

    def perform_download(self, file, show_progress):
        self.total_to_download += self.file_size
        self.now_downloaded = 0
        self.start_time = time.time()
        accumulated_size = 0
        last_update_time = time.time()
        try:
            while True:
                data = self.response.read(1024)
                if not data:
                    break

                size = file.write(data)
                if show_progress:
                    accumulated_size += size
                    if time.time() - last_update_time >= 0.1:
                        self.update_progress(accumulated_size)
                        accumulated_size = 0
                        last_update_time = time.time()

            if show_progress:
                if accumulated_size > 0:
                    self.update_progress(accumulated_size)
        finally:
            if show_progress:
                # Output a newline after the progress bar
                perror("")

    def human_readable_time(self, seconds):
        hrs = int(seconds) // 3600
        mins = (int(seconds) % 3600) // 60
        secs = int(seconds) % 60
        width = 10
        if hrs > 0:
            return f"{hrs}h {mins:02}m {secs:02}s".rjust(width)
        elif mins > 0:
            return f"{mins}m {secs:02}s".rjust(width)
        else:
            return f"{secs}s".rjust(width)

    def human_readable_size(self, size):
        width = 10
        for unit in ["B", "KB", "MB", "GB", "TB"]:
            if size < 1024:
                return f"{size:.2f} {unit}".rjust(width)

            size /= 1024

        return f"{size:.2f} PB".rjust(width)

    def get_terminal_width(self):
        return shutil.get_terminal_size().columns

    def generate_progress_prefix(self, percentage):
        return f"{percentage}% |".rjust(6)

    def generate_progress_suffix(self, now_downloaded_plus_file_size, speed, estimated_time):
        return f"{self.human_readable_size(now_downloaded_plus_file_size)}/{self.human_readable_size(self.total_to_download)}{self.human_readable_size(speed)}/s{self.human_readable_time(estimated_time)}"  # noqa: E501

    def calculate_progress_bar_width(self, progress_prefix, progress_suffix):
        progress_bar_width = self.get_terminal_width() - len(progress_prefix) - len(progress_suffix) - 3
        if progress_bar_width < 1:
            progress_bar_width = 1

        return progress_bar_width

    def generate_progress_bar(self, progress_bar_width, percentage):
        pos = (percentage * progress_bar_width) // 100
        progress_bar = ""
        for i in range(progress_bar_width):
            progress_bar += "█" if i < pos else " "

        return progress_bar

    def set_resume_point(self, output_file):
        if output_file and os.path.exists(output_file):
            return os.path.getsize(output_file)

        return 0

    def print_progress(self, progress_prefix, progress_bar, progress_suffix):
        perror(f"\r{progress_prefix}{progress_bar}| {progress_suffix}", end="")

    def update_progress(self, chunk_size):
        self.now_downloaded += chunk_size
        now_downloaded_plus_file_size = self.now_downloaded + self.file_size
        percentage = (now_downloaded_plus_file_size * 100) // self.total_to_download if self.total_to_download else 100
        progress_prefix = self.generate_progress_prefix(percentage)
        speed = self.calculate_speed(self.now_downloaded, self.start_time)
        tim = (self.total_to_download - self.now_downloaded) // speed
        progress_suffix = self.generate_progress_suffix(now_downloaded_plus_file_size, speed, tim)
        progress_bar_width = self.calculate_progress_bar_width(progress_prefix, progress_suffix)
        progress_bar = self.generate_progress_bar(progress_bar_width, percentage)
        self.print_progress(progress_prefix, progress_bar, progress_suffix)

    def calculate_speed(self, now_downloaded, start_time):
        now = time.time()
        elapsed_seconds = now - start_time
        return now_downloaded / elapsed_seconds


def download_file(url: str, dest_path: str, headers: Optional[dict[str, str]] = None, show_progress: bool = True):
    """
    Downloads a file from a given URL to a specified destination path.

    Args:
        url (str): The URL to download from.
        dest_path (str): The path to save the downloaded file.
        headers (dict): Optional headers to include in the request.
        show_progress (bool): Whether to show a progress bar during download.

    Raises:
        RuntimeError: If the download fails after multiple attempts.
    """
    headers = headers or {}

    # If not running in a TTY, disable progress to prevent CI pollution
    if not sys.stdout.isatty():
        show_progress = False

    http_client = HttpClient()
    max_retries = ActiveConfig().http_client.max_retries
    retries = 0

    while retries <= max_retries:
        try:
            # Initialize HTTP client for the request
            http_client.init(url=url, headers=headers, output_file=dest_path, show_progress=show_progress)
            return  # Exit function if successful

        except KeyboardInterrupt:
            perror("\nDownload interrupted by user. Exiting cleanly.")
            raise

        except urllib.error.HTTPError as e:
            if e.code in [HTTP_RANGE_NOT_SATISFIABLE, HTTP_NOT_FOUND]:
                raise e
            retries += 1

        except urllib.error.URLError as e:
            console.error(f"Network Error: {e.reason}")
            retries += 1

        except TimeoutError:
            retries += 1
            console.warning(f"TimeoutError: The server took too long to respond. Retrying {retries}/{max_retries} ...")

        except RuntimeError as e:  # Catch network-related errors from HttpClient
            retries += 1
            console.warning(f"{e}. Retrying {retries}/{max_retries} ...")

        except IOError as e:
            retries += 1
            console.warning(f"I/O Error: {e}. Retrying {retries}/{max_retries} ...")

        except Exception as e:
            console.error(f"Unexpected error: {str(e)}")
            raise e

        if retries > max_retries:
            error_message = (
                "\nDownload failed after multiple attempts.\n"
                "Possible causes:\n"
                "- Internet connection issue\n"
                "- Server is down or unresponsive\n"
                "- Firewall or proxy blocking the request\n"
            )
            raise ConnectionError(error_message)

        time.sleep(
            min(ActiveConfig().http_client.max_retry_delay, 2 ** (retries - 1) * 0.1)
        )  # Exponential backoff (0.1s, 0.2s, 0.4s... max_retry_delay)
