"""Small rendering helpers shared by the widgets.

Every colour in the UI is an ANSI palette name (``cyan``, ``bright_magenta``,
``dim`` …), never an RGB value.  That way the TUI adopts whatever colours the
terminal is configured with, and nothing sets a background colour, so
transparent terminals stay transparent.
"""

from __future__ import annotations

import hashlib
import math
import os
import time
from datetime import datetime, timezone, tzinfo
from functools import lru_cache
from zoneinfo import ZoneInfo

from rich.cells import cell_len
from rich.text import Text

LOCALTIME_PATH = "/etc/localtime"
_UTC_NAMES = {"UTC", "UCT", "GMT", "ETC/UTC", "ETC/UCT", "ETC/GMT", "Z"}

LEVELS = " ▁▂▃▄▅▆▇█"

# Bottom-to-top spectrum colours, picked from the terminal's stock ANSI palette.
SPECTRUM_STOPS = (
    "cyan",
    "blue",
    "magenta",
    "bright_magenta",
    "yellow",
    "bright_yellow",
    "red",
)

ART_STOPS = ("blue", "magenta", "bright_magenta", "yellow", "cyan", "green")

STATE_STYLE = {
    "playing": ("●", "green"),
    "loading": ("◌", "yellow"),
    "buffering": ("◌", "yellow"),
    "paused": ("❚❚", "magenta"),
    "stopped": ("○", "bright_black"),
    "error": ("✕", "red"),
}


def truncate(text: str, width: int) -> str:
    if width <= 0:
        return ""
    if cell_len(text) <= width:
        return text
    if width == 1:
        return "…"
    kept: list[str] = []
    used = 0
    for char in text:
        char_width = cell_len(char)
        if used + char_width > width - 1:
            break
        kept.append(char)
        used += char_width
    return "".join(kept) + "…"


def fit(text: str, width: int) -> str:
    clipped = truncate(text, width)
    return clipped + " " * max(0, width - cell_len(clipped))


def compact_count(value: int) -> str:
    if value <= 0:
        return "—"
    if value >= 1_000_000:
        return f"{value / 1_000_000:.1f}M"
    if value >= 1_000:
        return f"{value / 1_000:.1f}k"
    return str(value)


def time_ago(moment: datetime | None, now: datetime | None = None) -> str:
    if moment is None:
        return ""
    now = now or datetime.now(timezone.utc)
    if moment.tzinfo is None:
        moment = moment.replace(tzinfo=timezone.utc)
    seconds = max(0, int((now - moment).total_seconds()))
    if seconds < 60:
        return f"{seconds}s ago"
    if seconds < 3600:
        return f"{seconds // 60}m ago"
    if seconds < 86_400:
        return f"{seconds // 3600}h ago"
    return f"{seconds // 86_400}d ago"


def _zone_from_file(path: str) -> tzinfo | None:
    try:
        with open(path, "rb") as handle:
            return ZoneInfo.from_file(handle)
    except (OSError, ValueError):
        return None


@lru_cache(maxsize=1)
def local_zone() -> tzinfo:
    """Return the user's local timezone.

    A nix-shell (or an FHS environment) can inherit a build-time ``TZ=UTC``,
    which would otherwise make Python show UTC.  Prefer an explicit non-UTC
    ``TZ``, then the system's ``/etc/localtime`` (the host's configured zone),
    and only then Python's idea of local time.
    """
    tz_name = (os.environ.get("TZ") or "").strip()
    if tz_name and tz_name.upper() not in _UTC_NAMES:
        try:
            return ZoneInfo(tz_name)
        except Exception:
            pass

    zone = _zone_from_file(LOCALTIME_PATH)
    if zone is not None:
        return zone

    if tz_name:
        try:
            return ZoneInfo(tz_name)
        except Exception:
            pass
    return datetime.now().astimezone().tzinfo or timezone.utc


def _local(moment: datetime | None) -> datetime:
    zone = local_zone()
    if moment is None:
        return datetime.now(zone)
    if moment.tzinfo is None:
        return moment.replace(tzinfo=zone)
    return moment.astimezone(zone)


def clock_time(moment: datetime | None = None) -> str:
    return _local(moment).strftime("%H:%M:%S")


def date_label(moment: datetime | None = None) -> str:
    return _local(moment).strftime("%a %d %b")


def local_time(moment: datetime | None) -> str:
    if moment is None:
        return "--:--"
    return _local(moment).strftime("%H:%M")


def gradient(stops: tuple[str, ...], position: float) -> str:
    """Pick a colour from a stock palette (no RGB interpolation)."""
    if not stops:
        return "white"
    position = max(0.0, min(1.0, position))
    index = min(len(stops) - 1, int(position * len(stops)))
    return stops[index]


def marquee(
    text: str, width: int, now: float | None = None, speed: float = 7.0, gap: int = 5
) -> str:
    if width <= 0:
        return ""
    if cell_len(text) <= width:
        return text
    now = time.monotonic() if now is None else now
    cycle = text + " " * gap
    length = max(1, cell_len(cycle))
    offset = int(now * speed) % length
    return truncate(cycle[offset:] + cycle[:offset], width)


def state_glyph(state: str) -> tuple[str, str]:
    return STATE_STYLE.get(state, STATE_STYLE["stopped"])


def art_lines(key: str, width: int, height: int) -> list[Text]:
    """Procedural album art as a solid ANSI-colour mosaic.

    Filled block glyphs are used (never cell backgrounds), so the cover is
    opaque while everything around it stays transparent.
    """
    width = max(1, width)
    height = max(1, height)
    seed = int(hashlib.sha1(key.encode("utf-8")).hexdigest()[:12], 16)

    lines: list[Text] = []
    for row in range(height):
        line = Text(no_wrap=True)
        ny = row / max(1, height - 1)
        for column in range(width):
            nx = column / max(1, width - 1)
            wave = 0.5 + 0.5 * math.sin(nx * 2.9 + ny * 2.1 + (seed % 11))
            position = (nx * 0.55 + (1.0 - ny) * 0.30 + wave * 0.15) % 1.0
            colour = gradient(ART_STOPS, position)
            # Mostly solid blocks with a little texture, like a tiny cover.
            glyph = "█" if ((seed + column * 7 + row * 11) % 17) not in (0, 5) else "▓"
            line.append(glyph, style=colour)
        lines.append(line)
    return lines


def rule(width: int, color: str = "bright_black", char: str = "─") -> Text:
    return Text(char * max(0, width), style=color)