"""Writes client/ios/App/TREKWidgets/WorldGrid.swift: the world as a grid of dots,
each with the ISO code of the country under it, for the atlas widget.

Run from the repo root after the country shapes change:
    python client/ios/WidgetPreviews/make-world-grid.py
Reads server/assets/atlas/admin0.geojson.gz, the same shapes the Atlas page draws.
"""
import gzip
import json

COLS, ROWS = 76, 34
LAT_TOP, LAT_BOTTOM = 80.0, -58.0  # Antarctica and the far north stay off the map
SOURCE = 'server/assets/atlas/admin0.geojson.gz'
TARGET = 'client/ios/App/TREKWidgets/WorldGrid.swift'


def rings(geometry):
    if geometry['type'] == 'Polygon':
        yield geometry['coordinates']
    elif geometry['type'] == 'MultiPolygon':
        yield from geometry['coordinates']


def inside(ring, x, y):
    hit = False
    j = len(ring) - 1
    for i in range(len(ring)):
        xi, yi = ring[i][0], ring[i][1]
        xj, yj = ring[j][0], ring[j][1]
        if (yi > y) != (yj > y) and x < (xj - xi) * (y - yi) / ((yj - yi) or 1e-12) + xi:
            hit = not hit
        j = i
    return hit


def in_polygon(polygon, x, y):
    return inside(polygon[0], x, y) and not any(inside(hole, x, y) for hole in polygon[1:])


features = []
for feature in json.load(gzip.open(SOURCE))['features']:
    code = feature['properties'].get('ISO_A2') or ''
    if len(code) != 2 or not code.isalpha():
        continue
    for polygon in rings(feature['geometry']):
        xs = [p[0] for p in polygon[0]]
        ys = [p[1] for p in polygon[0]]
        features.append((code, (min(xs), min(ys), max(xs), max(ys)), polygon))

# Each cell is sampled at five points, so a narrow country still claims its dot.
offsets = [(0.5, 0.5), (0.25, 0.25), (0.75, 0.25), (0.25, 0.75), (0.75, 0.75)]
cell_w = 360.0 / COLS
cell_h = (LAT_TOP - LAT_BOTTOM) / ROWS
rows = []
for r in range(ROWS):
    row = []
    for c in range(COLS):
        votes = {}
        for ox, oy in offsets:
            x = -180 + (c + ox) * cell_w
            y = LAT_TOP - (r + oy) * cell_h
            for code, (x0, y0, x1, y1), polygon in features:
                if x0 <= x <= x1 and y0 <= y <= y1 and in_polygon(polygon, x, y):
                    votes[code] = votes.get(code, 0) + 1
                    break
        row.append(max(votes, key=votes.get) if votes else '..')
    rows.append(''.join(row))

land = sum(len(r) // 2 - r.count('..') for r in rows)
body = '\n'.join(f'        "{r}",' for r in rows)
swift = f'''// Generated by client/ios/WidgetPreviews/make-world-grid.py from
// server/assets/atlas/admin0.geojson.gz; do not edit by hand.
import Foundation

/// The world as {COLS} by {ROWS} dots from {LAT_TOP:g}° north to {-LAT_BOTTOM:g}° south,
/// each the ISO code of the country under it, ".." for sea ({land} land dots).
enum WorldGrid {{
    static let columns = {COLS}
    static let rows: [String] = [
{body}
    ]

    /// The country code of a dot, nil for sea.
    static func code(row: Int, column: Int) -> String? {{
        let line = rows[row]
        let start = line.index(line.startIndex, offsetBy: column * 2)
        let code = String(line[start..<line.index(start, offsetBy: 2)])
        return code == ".." ? nil : code
    }}
}}
'''
open(TARGET, 'w', encoding='utf8', newline='\n').write(swift)
print('land dots', land)