"""Regenerate assets/downloads-chart.svg from pypistats.org data.

Fetches daily download counts for pbi-cli-tool (mirrors excluded), computes a
cumulative series, and writes a dark-theme SVG line chart that matches the
visual style of the other assets in this repo.

Runs with stdlib only so it works in CI without extra dependencies.

Usage:
    python scripts/generate_downloads_chart.py
"""

from __future__ import annotations

import json
import sys
import urllib.request
from datetime import date, datetime
from pathlib import Path

PACKAGE = "pbi-cli-tool"
API_URL = f"https://pypistats.org/api/packages/{PACKAGE}/overall?mirrors=false"
OUTPUT_PATH = Path(__file__).resolve().parent.parent / "assets" / "downloads-chart.svg"

# Chart geometry
WIDTH = 850
HEIGHT = 340
PLOT_LEFT = 70
PLOT_RIGHT = 810
PLOT_TOP = 78
PLOT_BOTTOM = 280

# Colors (match stats.svg / banner.svg palette)
BG = "#0d1117"
ACCENT_YELLOW = "#F2C811"
LINE_BLUE = "#58a6ff"
GRID = "#21262d"
TEXT_PRIMARY = "#c9d1d9"
TEXT_SECONDARY = "#8b949e"
CARD_BG = "#0d1a2a"


def fetch_downloads() -> list[tuple[date, int]]:
    """Return sorted list of (date, daily_downloads) from pypistats."""
    with urllib.request.urlopen(API_URL, timeout=30) as resp:
        payload = json.loads(resp.read())

    rows = [
        (datetime.strptime(r["date"], "%Y-%m-%d").date(), int(r["downloads"]))
        for r in payload["data"]
        if r["category"] == "without_mirrors"
    ]
    rows.sort(key=lambda item: item[0])
    return rows


def to_cumulative(rows: list[tuple[date, int]]) -> list[tuple[date, int]]:
    total = 0
    out: list[tuple[date, int]] = []
    for d, n in rows:
        total += n
        out.append((d, total))
    return out


def nice_ceiling(value: int) -> int:
    """Round up to a nice axis maximum (1-2-5 * 10^n)."""
    if value <= 0:
        return 10
    import math

    exp = math.floor(math.log10(value))
    base = 10**exp
    for step in (1, 2, 2.5, 5, 10):
        candidate = int(step * base)
        if candidate >= value:
            return candidate
    return int(10 * base)


def build_svg(series: list[tuple[date, int]]) -> str:
    if not series:
        raise RuntimeError("No download data returned from pypistats")

    n = len(series)
    max_val = series[-1][1]
    y_max = nice_ceiling(int(max_val * 1.15))

    plot_width = PLOT_RIGHT - PLOT_LEFT
    plot_height = PLOT_BOTTOM - PLOT_TOP

    def x_at(i: int) -> float:
        if n == 1:
            return PLOT_LEFT + plot_width / 2
        return PLOT_LEFT + (i / (n - 1)) * plot_width

    def y_at(v: int) -> float:
        return PLOT_BOTTOM - (v / y_max) * plot_height

    points = [(x_at(i), y_at(v)) for i, (_, v) in enumerate(series)]

    line_path = "M " + " L ".join(f"{x:.2f},{y:.2f}" for x, y in points)
    area_path = (
        f"M {points[0][0]:.2f},{PLOT_BOTTOM} "
        + "L "
        + " L ".join(f"{x:.2f},{y:.2f}" for x, y in points)
        + f" L {points[-1][0]:.2f},{PLOT_BOTTOM} Z"
    )

    # Y-axis gridlines (5 steps)
    gridlines = []
    y_labels = []
    for step in range(6):
        v = y_max * step / 5
        y = PLOT_BOTTOM - (v / y_max) * plot_height
        gridlines.append(
            f'<line x1="{PLOT_LEFT}" y1="{y:.1f}" x2="{PLOT_RIGHT}" y2="{y:.1f}" '
            f'stroke="{GRID}" stroke-width="1" stroke-dasharray="2,3"/>'
        )
        label = f"{int(v):,}"
        y_labels.append(
            f'<text x="{PLOT_LEFT - 8}" y="{y + 4:.1f}" font-family="\'Segoe UI\', Arial, sans-serif" '
            f'font-size="10" fill="{TEXT_SECONDARY}" text-anchor="end">{label}</text>'
        )

    # X-axis labels: first, last, and ~3 intermediate
    label_indices = sorted({0, n - 1, n // 4, n // 2, (3 * n) // 4})
    x_labels = []
    for i in label_indices:
        d, _ = series[i]
        x = x_at(i)
        x_labels.append(
            f'<text x="{x:.1f}" y="{PLOT_BOTTOM + 18}" font-family="\'Segoe UI\', Arial, sans-serif" '
            f'font-size="10" fill="{TEXT_SECONDARY}" text-anchor="middle">{d.strftime("%b %d")}</text>'
        )

    # Data point dots + highlight on last
    dots = []
    for i, (x, y) in enumerate(points):
        is_last = i == n - 1
        r = 4 if is_last else 2.5
        fill = ACCENT_YELLOW if is_last else LINE_BLUE
        dots.append(f'<circle cx="{x:.2f}" cy="{y:.2f}" r="{r}" fill="{fill}"/>')

    # Last-value callout
    last_x, last_y = points[-1]
    last_val = series[-1][1]
    callout_x = min(last_x + 10, PLOT_RIGHT - 90)
    callout_y = max(last_y - 28, PLOT_TOP + 14)

    # Summary stats
    first_date = series[0][0].strftime("%b %d, %Y")
    last_date = series[-1][0].strftime("%b %d, %Y")
    total_str = f"{max_val:,}"

    svg = f"""<svg xmlns="http://www.w3.org/2000/svg" width="{WIDTH}" height="{HEIGHT}" viewBox="0 0 {WIDTH} {HEIGHT}">
  <defs>
    <linearGradient id="areaFill" x1="0" y1="0" x2="0" y2="1">
      <stop offset="0%" stop-color="{LINE_BLUE}" stop-opacity="0.45"/>
      <stop offset="100%" stop-color="{LINE_BLUE}" stop-opacity="0"/>
    </linearGradient>
  </defs>

  <!-- Background -->
  <rect width="100%" height="100%" fill="{BG}" rx="8"/>

  <!-- Title -->
  <text x="{WIDTH // 2}" y="33" font-family="'Segoe UI', Arial, sans-serif" font-size="17" fill="{ACCENT_YELLOW}" text-anchor="middle" font-weight="bold">pbi-cli Downloads Over Time</text>
  <text x="{WIDTH // 2}" y="52" font-family="'Segoe UI', Arial, sans-serif" font-size="11" fill="{TEXT_SECONDARY}" text-anchor="middle">Cumulative installs from PyPI \u2022 mirrors excluded \u2022 source: pypistats.org</text>

  <!-- Gridlines & y-labels -->
  {"".join(gridlines)}
  {"".join(y_labels)}

  <!-- Area fill -->
  <path d="{area_path}" fill="url(#areaFill)"/>

  <!-- Line -->
  <path d="{line_path}" fill="none" stroke="{LINE_BLUE}" stroke-width="2.5" stroke-linejoin="round" stroke-linecap="round"/>

  <!-- Data points -->
  {"".join(dots)}

  <!-- Last-value callout -->
  <rect x="{callout_x:.1f}" y="{callout_y:.1f}" width="82" height="24" rx="4" fill="{CARD_BG}" stroke="{ACCENT_YELLOW}" stroke-width="1"/>
  <text x="{callout_x + 41:.1f}" y="{callout_y + 16:.1f}" font-family="'Segoe UI', Arial, sans-serif" font-size="12" fill="{ACCENT_YELLOW}" text-anchor="middle" font-weight="bold">{total_str} total</text>

  <!-- X-axis labels -->
  {"".join(x_labels)}

  <!-- Footer: date range -->
  <text x="{PLOT_LEFT}" y="{HEIGHT - 12}" font-family="'Segoe UI', Arial, sans-serif" font-size="10" fill="{TEXT_SECONDARY}">{first_date} \u2192 {last_date}</text>
  <text x="{PLOT_RIGHT}" y="{HEIGHT - 12}" font-family="'Segoe UI', Arial, sans-serif" font-size="10" fill="{TEXT_SECONDARY}" text-anchor="end">{n} days of data</text>
</svg>
"""
    return svg


def main() -> int:
    try:
        daily = fetch_downloads()
    except Exception as exc:  # noqa: BLE001
        print(f"Failed to fetch pypistats data: {exc}", file=sys.stderr)
        return 1

    if not daily:
        print("pypistats returned no rows", file=sys.stderr)
        return 1

    cumulative = to_cumulative(daily)
    svg = build_svg(cumulative)

    OUTPUT_PATH.parent.mkdir(parents=True, exist_ok=True)
    OUTPUT_PATH.write_text(svg, encoding="utf-8")
    print(f"Wrote {OUTPUT_PATH} ({len(cumulative)} days, {cumulative[-1][1]:,} total downloads)")
    return 0


if __name__ == "__main__":
    sys.exit(main())