#!/usr/bin/env python3
"""Convert an OSM API XML dump to overpass-style JSON for build_level_osm.py.

Usage: osm_xml_to_json.py <in.xml> <out.json>

Emits ways (tags+nodes+geometry), tree nodes, and assembles water multipolygon
relations (the Brisbane River is a relation, not a way) into synthetic closed
ways tagged natural=water.
"""
import json
import sys
import xml.etree.ElementTree as ET

root = ET.parse(sys.argv[1]).getroot()
nodes = {}
elements = []

for n in root.iter("node"):
    nid = int(n.get("id"))
    lat, lon = float(n.get("lat")), float(n.get("lon"))
    nodes[nid] = (lat, lon)
    tags = {t.get("k"): t.get("v") for t in n.findall("tag")}
    if tags.get("natural") == "tree":
        elements.append({"type": "node", "id": nid, "tags": tags, "lat": lat, "lon": lon})

ways = {}
for w in root.iter("way"):
    wid = int(w.get("id"))
    tags = {t.get("k"): t.get("v") for t in w.findall("tag")}
    nds = [int(nd.get("ref")) for nd in w.findall("nd")]
    if not all(r in nodes for r in nds) or len(nds) < 2:
        continue
    ways[wid] = nds
    if any(tags.get(k) for k in ("building", "highway", "leisure", "landuse", "natural", "water", "waterway")):
        elements.append({"type": "way", "id": wid, "tags": tags, "nodes": nds,
                         "geometry": [{"lat": nodes[r][0], "lon": nodes[r][1]} for r in nds]})

# water multipolygons: join outer member ways into rings
def assemble(rings_nodes):
    segs = [list(s) for s in rings_nodes if len(s) >= 2]
    rings = []
    while segs:
        ring = segs.pop()
        grew = True
        while grew and ring[0] != ring[-1]:
            grew = False
            for i, s in enumerate(segs):
                if s[0] == ring[-1]:
                    ring += s[1:]
                elif s[-1] == ring[-1]:
                    ring += list(reversed(s))[1:]
                elif s[-1] == ring[0]:
                    ring = s + ring[1:]
                elif s[0] == ring[0]:
                    ring = list(reversed(s)) + ring[1:]
                else:
                    continue
                segs.pop(i)
                grew = True
                break
        if ring[0] == ring[-1] and len(ring) > 3:
            rings.append(ring)
    return rings

synth = 1
for r in root.iter("relation"):
    tags = {t.get("k"): t.get("v") for t in r.findall("tag")}
    if not (tags.get("natural") == "water" or tags.get("water") or tags.get("waterway") == "riverbank"):
        continue
    outers = [ways[int(m.get("ref"))] for m in r.findall("member")
              if m.get("type") == "way" and m.get("role") in ("outer", "") and int(m.get("ref")) in ways]
    for ring in assemble(outers):
        elements.append({"type": "way", "id": 10**10 + synth, "tags": {"natural": "water"},
                         "nodes": ring, "geometry": [{"lat": nodes[n][0], "lon": nodes[n][1]} for n in ring]})
        synth += 1

json.dump({"elements": elements}, open(sys.argv[2], "w"))
b = sum(1 for e in elements if e.get("tags", {}).get("building"))
h = sum(1 for e in elements if e.get("tags", {}).get("highway"))
w = sum(1 for e in elements if e.get("tags", {}).get("natural") == "water" or e.get("tags", {}).get("water"))
t = sum(1 for e in elements if e["type"] == "node")
print("converted: %d buildings, %d highways, %d water polys, %d trees" % (b, h, w, t))