from __future__ import annotations

import argparse
import threading
import tkinter as tk
from tkinter import messagebox
from collections.abc import Sequence
from functools import lru_cache
from pathlib import Path
from queue import Empty, Queue
from threading import Thread

from pdf2image import convert_from_path
from PIL import Image, ImageTk

from copienator import (
    CliError,
    EvaluationWorkspace,
    ExitCode,
    atomic_write_json,
    execute,
    target_parser,
    workspace_from_target,
)
from copienator.filesystem import staged_files
from copienator.copy_errors import clear_copy_error, mark_copy_error, marked_copy_paths

DELIMITER_WIDTH = 5
DELIMITER_COLOR = (0, 0, 0)
OUTPUT_SIZE = (1800, 1000)
pdf_cache_lock = threading.Lock()


def distribute_pages(total_pages: int, max_per_file: int = 5) -> list[int]:
    """Distribute pages into balanced chunks no larger than max_per_file."""
    if total_pages == 0:
        return []
    number_of_files = (total_pages + max_per_file - 1) // max_per_file
    base_count, remainder = divmod(total_pages, number_of_files)
    return [
        base_count + (1 if index < remainder else 0)
        for index in range(number_of_files)
    ]


def stitch_images(image_list: list[Image.Image]) -> Image.Image | None:
    if not image_list:
        return None
    total_width = sum(image.width for image in image_list)
    total_width += (len(image_list) - 1) * DELIMITER_WIDTH
    max_height = max(image.height for image in image_list)
    combined = Image.new("RGB", (total_width, max_height), color="white")
    x_offset = 0
    for index, image in enumerate(image_list):
        combined.paste(image, (x_offset, 0))
        x_offset += image.width
        if index < len(image_list) - 1:
            delimiter = Image.new(
                "RGB", (DELIMITER_WIDTH, max_height), color=DELIMITER_COLOR
            )
            combined.paste(delimiter, (x_offset, 0))
            x_offset += DELIMITER_WIDTH
    return combined


@lru_cache(maxsize=3)
def _get_pdf_pages_cached(pdf_path: Path) -> list[Image.Image]:
    # Label coordinates use the full, displayed MediaBox, including on PDFs
    # previously cropped by crop-margins. Keep this in sync with split-answers.
    return convert_from_path(pdf_path, use_cropbox=False)


def get_pdf_pages(pdf_path: Path) -> list[Image.Image]:
    """Thread-safe wrapper around the small PDF conversion cache."""
    with pdf_cache_lock:
        return _get_pdf_pages_cached(pdf_path)


def process_single_pdf(
    pdf_path: Path,
    shift_offset: int = 0,
    max_per_file: int = 5,
) -> tuple[Image.Image, list[Image.Image], dict[str, object]] | None:
    """Convert one PDF into a preview, full-resolution splits and metadata."""
    try:
        cropped_images = []
        for image in get_pdf_pages(pdf_path):
            width, height = image.size
            if max_per_file == 1:
                left, right = 0, width
            else:
                left = max(0, 100 + shift_offset)
                right = min(width, width // 3 + 100 + shift_offset)
            if right > left:
                cropped_images.append(image.crop((left, 0, right, height)))
        if not cropped_images:
            return None

        distribution = distribute_pages(len(cropped_images), max_per_file)
        split_images = []
        current_index = 0
        for count in distribution:
            stitched = stitch_images(cropped_images[current_index : current_index + count])
            if stitched is not None:
                split_images.append(stitched)
            current_index += count
        full_stitch = stitch_images(cropped_images)
        if full_stitch is None:
            return None
        preview = full_stitch.resize(OUTPUT_SIZE, Image.Resampling.BILINEAR)
        schema: dict[str, object] = {
            "original_filename": pdf_path.name,
            "total_pages": len(cropped_images),
            "number_of_files": len(split_images),
            "columns_per_file": distribution,
        }
        return preview, split_images, schema
    except Exception as exc:  # noqa: BLE001 - interactive item failure
        print(f"Error processing {pdf_path.name}: {exc}")
        return None


def _previous_cutleft_outputs(output_dir: Path, base_name: str) -> set[str]:
    if not output_dir.is_dir():
        return set()
    result = {f"{base_name}_schema.json"}
    for path in output_dir.glob(f"{base_name}_*.jpg"):
        suffix = path.stem.removeprefix(f"{base_name}_")
        if suffix.isdigit():
            result.add(path.name)
    return result


def save_results(
    result: tuple[Image.Image, list[Image.Image], dict[str, object]],
    pdf_path: Path,
    output_dir: Path,
) -> None:
    """Atomically replace every Cutleft output associated with one copy."""
    _, splits, schema = result
    base_name = pdf_path.stem
    previous = _previous_cutleft_outputs(output_dir, base_name)
    with staged_files(output_dir, remove=previous) as staging:
        for index, image in enumerate(splits, start=1):
            filename = f"{base_name}_{index:02d}.jpg"
            image.save(staging / filename, "JPEG", quality=95)
        atomic_write_json(staging / f"{base_name}_schema.json", schema)
    for index in range(1, len(splits) + 1):
        print(f"Saved: {base_name}_{index:02d}.jpg")
    print(f"Saved schema: {base_name}_schema.json")


class ImageReviewer:
    def __init__(
        self,
        files: list[Path],
        output_dir: Path,
        default_max_per_file: int = 5,
    ) -> None:
        self.files = files
        self.output_dir = output_dir
        self.workspace = EvaluationWorkspace(output_dir.parent)
        self.completed = False
        self.had_errors = False
        self.stop_prefetch = threading.Event()
        self.current_result = None
        self.index = 0
        self.current_shift = 0
        self.default_max_per_file = default_max_per_file
        self.current_max_per_file = default_max_per_file
        self.current_preview: Image.Image | None = None
        self.is_processing = False
        self.manual_queue: Queue[
            tuple[Image.Image, list[Image.Image], dict[str, object]] | None
        ] = Queue()

        self.root = tk.Tk()
        self.root.title("PDF Cropper")
        self.root.geometry("+100+100")
        self.label_img = tk.Label(self.root)
        self.label_img.pack()
        self.label_info = tk.Label(self.root, text="", font=("Arial", 12, "bold"))
        self.label_info.pack(pady=5)
        self.root.bind("<Return>", self.on_next)
        self.root.bind("s", self.on_skip)
        self.root.protocol("WM_DELETE_WINDOW", self.on_close)
        self.root.bind("n", lambda _event: self.on_shift(50))
        self.root.bind("N", lambda _event: self.on_shift(100))
        self.root.bind("t", lambda _event: self.on_shift(-50))
        self.root.bind("1", lambda _event: self.on_set_max_pages(1))

        Thread(target=self.prefetch_worker, daemon=True).start()
        self.load_current_image()
        self.root.lift()
        self.root.focus_force()
        self.root.mainloop()

    def on_set_max_pages(self, count: int) -> None:
        if self.is_processing:
            return
        self.current_max_per_file = count
        print(f"Setting max pages per file: {count}")
        self.trigger_processing(self.files[self.index], self.current_shift)

    def prefetch_worker(self) -> None:
        processed_index = -1
        while not self.stop_prefetch.is_set():
            target = self.index + 1
            if target < len(self.files) and target != processed_index:
                try:
                    get_pdf_pages(self.files[target])
                except Exception:
                    pass  # The foreground review reports and flags conversion errors.
                processed_index = target
            self.stop_prefetch.wait(0.05)

    def load_current_image(self) -> None:
        if self.index >= len(self.files):
            print("All files processed.")
            self.completed = True
            self.on_close()
            return
        self.is_processing = False
        self.current_shift = 0
        self.current_result = None
        self.trigger_processing(self.files[self.index], self.current_shift)

    def trigger_processing(self, pdf_path: Path, shift: int) -> None:
        self.is_processing = True
        self.label_info.configure(
            text=f"Processing {pdf_path.name} (Shift {shift})... Please wait.",
            fg="red",
        )

        def worker() -> None:
            self.manual_queue.put(
                process_single_pdf(pdf_path, shift, self.current_max_per_file)
            )

        Thread(target=worker, daemon=True).start()
        self.check_manual_queue(pdf_path)

    def check_manual_queue(self, pdf_path: Path) -> None:
        try:
            result = self.manual_queue.get_nowait()
            self.is_processing = False
            if result is None:
                print(f"Failed to process {pdf_path.name}, skipping.")
                self._mark_error(pdf_path, "Échec de la conversion pour la découpe des marges")
                self._advance()
            else:
                self.handle_processing_result(result, pdf_path)
        except Empty:
            self.root.after(100, lambda: self.check_manual_queue(pdf_path))

    def handle_processing_result(
        self,
        result: tuple[Image.Image, list[Image.Image], dict[str, object]],
        pdf_path: Path,
    ) -> None:
        self.current_preview = result[0]
        self.current_result = result
        self.update_display(pdf_path.name, result[2])

    def update_display(self, filename: str, schema: dict[str, object]) -> None:
        if self.current_preview is None:
            return
        tk_image = ImageTk.PhotoImage(self.current_preview)
        self.label_img.configure(image=tk_image)
        self.label_img.image = tk_image
        self.label_info.configure(
            text=(
                f"[{self.index + 1}/{len(self.files)}] {filename} | "
                f"Shift: {self.current_shift}px\nFiles: {schema['number_of_files']} | "
                f"Cols: {schema['columns_per_file']}\n"
                "Enter: Save and next | s: flag error and skip | n: +50 | N: +100 | t: -50 | "
                "1: use single column"
            ),
            fg="black",
        )

    def on_shift(self, amount: int) -> None:
        if self.is_processing:
            return
        self.current_shift += amount
        print(f"Applying shift: {self.current_shift}")
        self.trigger_processing(self.files[self.index], self.current_shift)

    def on_next(self, _event: object) -> None:
        if self.is_processing or self.current_result is None:
            return
        pdf_path = self.files[self.index]
        try:
            save_results(self.current_result, pdf_path, self.output_dir)
            clear_copy_error(self.workspace, pdf_path)
        except Exception as exc:
            self._mark_error(pdf_path, f"Échec de l’enregistrement : {exc}")
            messagebox.showerror("Enregistrement impossible", str(exc), parent=self.root)
            return
        self._advance()

    def _mark_error(self, pdf_path: Path, reason: str) -> None:
        mark_copy_error(self.workspace, pdf_path, reason)
        self.had_errors = True
        print(f"[Copie signalée] {pdf_path.name}: {reason}")

    def on_skip(self, _event=None) -> None:
        if self.is_processing or self.index >= len(self.files):
            return
        self._mark_error(self.files[self.index], "Problème repéré pendant la découpe des marges")
        self._advance()

    def on_close(self) -> None:
        self.stop_prefetch.set()
        self.root.destroy()

    def _advance(self) -> None:
        self.index += 1
        self.current_shift = 0
        self.current_max_per_file = self.default_max_per_file
        self.load_current_image()


def _selected_files(
    workspace: EvaluationWorkspace,
    target: Path,
) -> list[Path]:
    workspace.require_directories("Copies")
    if target.is_file():
        if target.suffix.casefold() != ".pdf":
            raise CliError(f"Target is not a PDF: {target}", ExitCode.INVALID_ARGUMENTS)
        return [target]
    return sorted(
        (
            path
            for path in workspace.copies_dir.glob("*.pdf")
            if "nonc" not in path.name.casefold()
        ),
        key=lambda path: path.name.casefold(),
    )


def run(
    workspace: EvaluationWorkspace,
    target: Path,
    *,
    fullpage: bool = False,
    marked: bool = False,
) -> ExitCode:
    files = marked_copy_paths(workspace) if marked else _selected_files(workspace, target)
    if not files:
        print("No PDF files found.")
        return ExitCode.SUCCESS
    workspace.cutleft_dir.mkdir(parents=True, exist_ok=True)
    _get_pdf_pages_cached.cache_clear()
    reviewer = ImageReviewer(
        files,
        workspace.cutleft_dir,
        default_max_per_file=1 if fullpage else 5,
    )
    if not reviewer.completed:
        return ExitCode.INTERRUPTED
    return ExitCode.PARTIAL if reviewer.had_errors else ExitCode.SUCCESS


def build_parser() -> argparse.ArgumentParser:
    parser = target_parser("Interactively crop the label margin from PDF copies")
    parser.add_argument("--marked", action="store_true", help="Review flagged copies and clear each flag after saving with Enter")
    parser.add_argument(
        "--fullpage",
        action="store_true",
        help="Use each complete page instead of cropping the label margin",
    )
    return parser


def main(argv: Sequence[str] | None = None) -> int:
    parser = build_parser()

    def handle(args: argparse.Namespace) -> ExitCode:
        workspace, target = workspace_from_target(args)
        return run(workspace, target, fullpage=args.fullpage, marked=args.marked)

    return execute(parser, argv, handle)


if __name__ == "__main__":
    raise SystemExit(main())