#!/usr/bin/env python3
"""DLit — Download It! 

a tiny terminal wrapper for yt-dlp.

Paste a link at the prompt; downloads queue and run serially in the
background. Commands: :mp3, :video, :none switch the active preset.
Ctrl-D or :q to quit.
"""

from __future__ import annotations

import os
import queue
import re
import readline  # noqa: F401  (importing enables line editing in input())
import shutil
import subprocess
import sys
import tempfile
import threading
import time
from pathlib import Path

import yt_dlp
from yt_dlp.postprocessor import EmbedThumbnailPP
from yt_dlp.postprocessor.common import PostProcessor

VERSION = "1.7"
DOWNLOAD_DIR = Path.home() / "Downloads"
PROMPT = "dlit> "

# A pasted link is first *resolved* (a quick, flat metadata fetch) to decide
# whether it is one video or a playlist. A playlist fans out into one queued
# job per entry, each labelled "(PlaylistName - i/N)". PLAYLIST_LIMIT bounds how
# many entries a single paste may expand into, so a pathological or effectively
# endless feed (e.g. youtube.com's recommendations) can't flood the queue.
PLAYLIST_LIMIT = 200
SOCKET_TIMEOUT = 30  # seconds; bounds network stalls during resolve + download

PRESETS: dict[str, dict] = {
    "mp3": {
        "format": "bestaudio/best",
        "writethumbnail": True,
        "postprocessors": [
            {"key": "FFmpegExtractAudio", "preferredcodec": "mp3", "preferredquality": "320"},
            {"key": "FFmpegMetadata"},
            # EmbedThumbnail is registered manually in worker() so that
            # SquareThumbnailCropper can run between metadata-write and embed.
        ],
        "postprocessor_args": {
            "metadata": [
                "-metadata", f"comment=DLit {VERSION} (Conway)",
                "-metadata", "genre=",
            ],
        },
    },
    "video": {"format": "bestvideo+bestaudio/best"},
    "none": {},
}

class _QuietLogger:
    """Swallow yt-dlp's own console output.

    yt-dlp writes errors/warnings straight to stderr even under quiet=True
    (see YoutubeDL.to_stderr). Those bytes bypass our cursor save/restore line
    management and land on top of the `dlit>` prompt, corrupting the display —
    most visibly on an invalid URL, which emits an "ERROR: ..." line. Routing
    everything through a logger keeps all output under our control; the failure
    itself still surfaces via the DownloadError that worker() catches.
    """

    def debug(self, msg: str) -> None: ...
    def info(self, msg: str) -> None: ...
    def warning(self, msg: str) -> None: ...
    def error(self, msg: str) -> None: ...


_QUIET_LOGGER = _QuietLogger()

_print_lock = threading.Lock()
_line_distance: dict[int, int] = {}  # job_id -> rows above the current cursor position
_job_title: dict[int, str] = {}      # job_id -> resolved title (once known)
_job_tag: dict[int, str] = {}        # job_id -> "(PlaylistName - i/N) " prefix, "" for singles

_RESET = "\x1b[0m"
ICON_QUEUED = f"\x1b[35m~{_RESET}"        # purple
ICON_DOWNLOADING = f"\x1b[33m↓{_RESET}"   # yellow
ICON_CONVERTING = f"\x1b[34m↻{_RESET}"    # blue
ICON_DONE = f"\x1b[32m✓{_RESET}"          # green
ICON_FAILED = f"\x1b[31m✗{_RESET}"        # red

_SGR_RE = re.compile(r"\x1b\[[0-9;]*m")


def _clamp(text: str) -> str:
    """Trim a status line to the terminal width, counting visible columns only.

    Job lines are rewritten in place by relying on each one occupying exactly
    one terminal row (see update_job_line). A line wider than the terminal wraps
    onto the row below — the prompt — and the cursor save/restore math no longer
    lands where it should, corrupting the display. Clamping keeps every line to a
    single row. SGR colour codes don't occupy columns, so they're copied through
    without counting toward the budget.
    """
    width = shutil.get_terminal_size((80, 24)).columns - 1
    if width <= 0:
        return text
    out: list[str] = []
    visible = i = 0
    while i < len(text):
        m = _SGR_RE.match(text, i)
        if m:
            out.append(m.group())
            i = m.end()
            continue
        if visible >= width:
            return "".join(out) + _RESET  # reset in case we cut mid-colour
        out.append(text[i])
        visible += 1
        i += 1
    return "".join(out)


def add_job_lines(items: list[tuple[int, str]]) -> None:
    """Main thread: print one or more new tracked lines above the next prompt.

    Submitting a link can fan out into several lines at once (one per playlist
    entry). Printing N lines pushes the next prompt down by N+1 rows — the N new
    lines plus the just-submitted prompt line that stays on screen — so every
    existing tracked line moves up by that much. The new lines, printed top to
    bottom, sit at distances N, N-1, … 1 above the coming prompt. With N=1 this
    reduces to the original "+= 2, new line at distance 1".
    """
    with _print_lock:
        n = len(items)
        for k in _line_distance:
            _line_distance[k] += n + 1
        for offset, (job_id, text) in enumerate(items):
            _line_distance[job_id] = n - offset
            sys.stdout.write(_clamp(text) + "\n")
        sys.stdout.flush()


def notice(text: str) -> None:
    """Main thread: print a one-off, untracked line above the next prompt."""
    with _print_lock:
        for k in _line_distance:
            _line_distance[k] += 2
        sys.stdout.write(_clamp(text) + "\n")
        sys.stdout.flush()


def update_job_line(job_id: int, text: str) -> None:
    """Worker thread: rewrite this job's tracked line in place; cursor returns to its prior spot."""
    with _print_lock:
        d = _line_distance.get(job_id)
        if d is None:
            return
        sys.stdout.write(
            "\x1b7"               # save cursor (DECSC)
            f"\x1b[{d}A"          # up d rows
            "\r\x1b[K"             # clear that line
            f"{_clamp(text)}"
            "\x1b8"               # restore cursor (DECRC)
        )
        sys.stdout.flush()


def make_opts(job_id: int, preset: str) -> dict:
    last = {"pct": -5.0, "t": 0.0}

    def progress(d: dict) -> None:
        info = d.get("info_dict") or {}
        title = info.get("title")
        if title:
            _job_title[job_id] = title
        status = d.get("status")
        tag = _job_tag.get(job_id, "")
        shown_title = tag + _job_title.get(job_id, "…")[:60]
        if status == "downloading":
            total = d.get("total_bytes") or d.get("total_bytes_estimate") or 0
            done = d.get("downloaded_bytes") or 0
            pct = (done * 100.0 / total) if total else 0.0
            now = time.monotonic()
            if pct - last["pct"] >= 5 or now - last["t"] >= 2.0:
                last["pct"], last["t"] = pct, now
                speed = d.get("speed") or 0
                speed_s = f"{speed / 1_000_000:4.1f} MB/s" if speed else "  - MB/s"
                update_job_line(
                    job_id,
                    f"[{ICON_DOWNLOADING}] {shown_title}   {pct:5.1f}%   {speed_s}",
                )
        elif status == "finished" and preset == "mp3":
            update_job_line(job_id, f"[{ICON_CONVERTING}] {shown_title}")

    return {
        "outtmpl": str(DOWNLOAD_DIR / "%(title)s.%(ext)s"),
        "noplaylist": True,
        "quiet": True,
        "no_warnings": True,
        "no_color": True,
        "noprogress": True,
        "logger": _QUIET_LOGGER,
        "socket_timeout": SOCKET_TIMEOUT,
        "progress_hooks": [progress],
        **PRESETS[preset],
    }


def resolve_opts() -> dict:
    """Options for the quick pre-download probe that classifies a pasted link.

    extract_flat keeps it cheap: playlist entries come back as bare references
    (id/title/url) without fetching each video. noplaylist=True preserves the
    download behaviour — a video that merely sits inside a playlist
    (watch?v=…&list=…) resolves to the single video; only a pure playlist or feed
    URL fans out. playlistend bounds how far an endless feed is walked.
    """
    return {
        "quiet": True,
        "no_warnings": True,
        "no_color": True,
        "noplaylist": True,
        "logger": _QUIET_LOGGER,
        "socket_timeout": SOCKET_TIMEOUT,
        "extract_flat": "in_playlist",
        "playlistend": PLAYLIST_LIMIT,
    }


def resolve(url: str) -> tuple[bool, str, list[tuple[str, str]]]:
    """Classify a pasted link. Returns (is_playlist, name, [(entry_url, title)]).

    A single video comes back as (False, title, [(url, title)]). A playlist or
    feed comes back as (True, playlist_name, [...]) — possibly empty, e.g. a
    logged-out recommendations feed, in which case nothing is queued.
    """
    with yt_dlp.YoutubeDL(resolve_opts()) as ydl:
        info = ydl.extract_info(url, download=False) or {}
    entries = info.get("entries")
    if entries is None:
        title = info.get("title") or url
        return False, title, [(info.get("webpage_url") or url, title)]
    name = info.get("title") or "playlist"
    items = []
    for e in entries:
        if not e:
            continue
        eurl = e.get("url") or e.get("webpage_url") or e.get("id")
        if eurl:
            items.append((eurl, e.get("title") or eurl))
    return True, name, items


class SquareThumbnailCropper(PostProcessor):
    """Detect a square cover image padded into a 16:9 YouTube thumbnail and crop
    the bars off before EmbedThumbnail runs.

    Works on bars of any solid color (black, white, the album's accent color,
    etc.) by sampling the leftmost/rightmost columns and walking inward until
    the column stops matching the edge color. Guarded by aspect ratio: if the
    detected content region isn't roughly square the original is left untouched,
    so YouTube videos with natively 16:9 thumbnails or artwork with uniform
    color edges that fool the sampler just pass through uncropped.
    """

    SQUARE_TOLERANCE = 0.05  # accept detected aspect ratios within ±5% of 1:1
    COLOR_TOLERANCE = 12     # per-channel RGB deviation a column may have from edge

    def run(self, info):
        path = self._thumbnail_path(info)
        if not path or not os.path.exists(path):
            return [], info
        crop = self._detect(path)
        if not crop:
            return [], info
        w, h, x, y = crop
        if h <= 0 or abs(w / h - 1.0) > self.SQUARE_TOLERANCE:
            return [], info
        self._apply(path, w, h, x, y)
        return [], info

    @staticmethod
    def _thumbnail_path(info: dict):
        for t in reversed(info.get("thumbnails") or []):
            fp = t.get("filepath")
            if fp:
                return fp
        return None

    @classmethod
    def _detect(cls, path: str):
        dims = cls._probe_dimensions(path)
        if not dims:
            return None
        w, h = dims
        buf = cls._dump_pixels(path, w, h)
        if buf is None:
            return None

        sample_ys = [h * i // 6 for i in range(1, 6)]
        tol = cls.COLOR_TOLERANCE

        def col_uniform(x: int, ref: tuple) -> bool:
            for y in sample_ys:
                i = (y * w + x) * 3
                if (abs(buf[i] - ref[0]) > tol
                        or abs(buf[i + 1] - ref[1]) > tol
                        or abs(buf[i + 2] - ref[2]) > tol):
                    return False
            return True

        def pix(x: int, y: int) -> tuple:
            i = (y * w + x) * 3
            return buf[i], buf[i + 1], buf[i + 2]

        left_ref = pix(0, h // 2)
        left_w = 0
        for x in range(w // 2):
            if not col_uniform(x, left_ref):
                break
            left_w = x + 1

        right_ref = pix(w - 1, h // 2)
        right_w = 0
        for x in range(w - 1, w // 2, -1):
            if not col_uniform(x, right_ref):
                break
            right_w += 1

        content_w = w - left_w - right_w
        if content_w <= 0:
            return None
        return content_w, h, left_w, 0

    @staticmethod
    def _probe_dimensions(path: str):
        try:
            res = subprocess.run(
                ["ffprobe", "-v", "error", "-select_streams", "v:0",
                 "-show_entries", "stream=width,height",
                 "-of", "csv=p=0", path],
                capture_output=True, text=True, timeout=10,
            )
        except (FileNotFoundError, subprocess.TimeoutExpired):
            return None
        if res.returncode != 0:
            return None
        parts = res.stdout.strip().split(",")
        if len(parts) != 2:
            return None
        try:
            w, h = int(parts[0]), int(parts[1])
        except ValueError:
            return None
        return (w, h) if w > 0 and h > 0 else None

    @staticmethod
    def _dump_pixels(path: str, w: int, h: int):
        try:
            res = subprocess.run(
                ["ffmpeg", "-hide_banner", "-loglevel", "error",
                 "-i", path, "-f", "rawvideo", "-pix_fmt", "rgb24", "-"],
                capture_output=True, timeout=15,
            )
        except (FileNotFoundError, subprocess.TimeoutExpired):
            return None
        if res.returncode != 0 or len(res.stdout) != w * h * 3:
            return None
        return res.stdout

    @staticmethod
    def _apply(path: str, w: int, h: int, x: int, y: int) -> None:
        suffix = os.path.splitext(path)[1] or ".jpg"
        # dir= keeps the temp file on the same filesystem as the target so the
        # final os.replace() is an atomic rename, not a cross-device error.
        fd, tmp = tempfile.mkstemp(suffix=suffix, dir=os.path.dirname(path) or ".")
        os.close(fd)
        try:
            subprocess.run(
                ["ffmpeg", "-hide_banner", "-loglevel", "error", "-y",
                 "-i", path, "-vf", f"crop={w}:{h}:{x}:{y}", tmp],
                check=True, capture_output=True, timeout=15,
            )
            os.replace(tmp, path)
        except (subprocess.CalledProcessError, subprocess.TimeoutExpired):
            try:
                os.unlink(tmp)
            except OSError:
                pass


def worker(jobs: "queue.Queue") -> None:
    while True:
        item = jobs.get()
        if item is None:
            return
        job_id, url, preset = item
        tag = _job_tag.get(job_id, "")
        try:
            with yt_dlp.YoutubeDL(make_opts(job_id, preset)) as ydl:
                if preset == "mp3":
                    ydl.add_post_processor(SquareThumbnailCropper(ydl), when="post_process")
                    ydl.add_post_processor(EmbedThumbnailPP(ydl), when="post_process")
                info = ydl.extract_info(url, download=True)
            title = (info or {}).get("title") or _job_title.get(job_id) or url
            _job_title[job_id] = title
            update_job_line(job_id, f"[{ICON_DONE}] {tag}{title[:60]}")
        except Exception as exc:  # noqa: BLE001
            err = str(exc).splitlines()[0][:60]
            title = _job_title.get(job_id) or url
            update_job_line(job_id, f"[{ICON_FAILED}] {tag}{title[:60]}   {err}")


def main() -> None:
    DOWNLOAD_DIR.mkdir(parents=True, exist_ok=True)
    jobs: "queue.Queue" = queue.Queue()
    threading.Thread(target=worker, args=(jobs,), daemon=True).start()

    preset = "mp3"
    next_id = 1
    print(f"dlit v.{VERSION}  ->  {DOWNLOAD_DIR}   preset={preset}   (:q to quit)")
    while True:
        try:
            line = input(PROMPT).strip()
        except (EOFError, KeyboardInterrupt):
            print()
            break
        if not line:
            continue
        if line.startswith(":"):
            cmd = line[1:]
            if cmd in ("q", "quit", "exit"):
                break
            if cmd in PRESETS:
                preset = cmd
                notice(f"  preset -> {preset}")
            else:
                notice(f"  unknown command: :{cmd}  (try :mp3, :video, :none, :q)")
            continue

        # A pasted link: resolve it (a quick network probe) to learn whether it's
        # a single video or a playlist, then queue one job per resulting entry.
        try:
            is_playlist, name, entries = resolve(line)
        except Exception as exc:  # noqa: BLE001
            err = str(exc).splitlines()[0][:60]
            add_job_lines([(next_id, f"[{ICON_FAILED}] {line}   {err}")])
            next_id += 1
            continue
        if not entries:
            notice(f"  nothing to download in '{name[:40]}'")
            continue

        total = len(entries)
        lines, pending = [], []
        for i, (entry_url, title) in enumerate(entries, 1):
            _job_title[next_id] = title
            if is_playlist:
                _job_tag[next_id] = f"({name[:24]} - {i}/{total}) "
            label = _job_tag.get(next_id, "") + title
            lines.append((next_id, f"[{ICON_QUEUED}] {label}"))
            pending.append((next_id, entry_url, preset))
            next_id += 1
        # Register the display lines before enqueuing, so a fast worker never
        # tries to update a line whose distance isn't set yet.
        add_job_lines(lines)
        for job in pending:
            jobs.put(job)


if __name__ == "__main__":
    main()