#!/usr/bin/env node

var fs = require("fs"),
    d3 = require("d3"),
    shapefile = require("shapefile"),
    dbf = require("../node_modules/shapefile/dbf"),
    Canvas = require("canvas"),
    queue = require("queue-async");

var regions = "01 02 03N 03S 03W 04 05 06 07 08 09 10U 10L 11 12 13 14 15 16 17 18".split(/\s+/),
    file = fs.createWriteStream(process.argv[2]);

var scale = 2,
    width = 960 * scale,
    height = 600 * scale;

var canvas = new Canvas(width, height),
    context = canvas.getContext("2d");

var projection = d3.geo.albers()
    .scale(1280 * scale)
    .translate([width * .5, height * .5])
    .precision(0);

var path = d3.geo.path()
    .projection(projection)
    .context(context);

var q = queue(1);
q.defer(renderLand);
regions.forEach(function(r) { q.defer(renderRegion, r); });
q.await(output);

function renderLand(callback) {
  var set = d3.set();
  console.log("rendering land outline");
  context.fillStyle = "#000";
  context.lineJoin = "round";

  shapefile.readStream("shp/land.shp")
      .on("feature", function(feature) {
        var id = feature.properties.STATE_FIPS;
        if (set.has(id)) return;
        set.add(id);
        context.beginPath();
        path(feature);
        context.fill();
      })
      .on("error", callback)
      .on("end", function() { callback(null); });
}

function renderRegion(region, callback) {
  console.log("loading attributes for " + region);
  var orderById = {};

  context.strokeStyle = "#fff";
  context.lineWidth = 1;
  context.lineCap = "round";
  context.lineJoin = "round";

  dbf.readStream("shp/" + region + "-attributes.dbf")
      .on("header", function(header) {
        if (header.fields[0].name !== "ComID") return void callback(new Error("ComID is not column 0"));
        if (header.fields[3].name !== "StreamOrde") return void callback(new Error("StreamOrde is not column 3"));
      })
      .on("record", function(record) { orderById[record[0]] = record[3]; })
      .on("error", callback)
      .on("end", readShapefile);

  function readShapefile() {
    console.log("rendering geometry for " + region);
    shapefile.readStream("shp/" + region + "-geometry.shp")
        .on("feature", function(feature) {
          var order = orderById[feature.properties.COMID] || orderById[feature.properties.ComID] || 1;
          context.lineWidth = order / 8;
          context.beginPath();
          path(feature);
          context.stroke();
        })
        .on("error", callback)
        .on("end", function() { callback(null); });
  }
}

function output(error) {
  if (error) throw error;
  console.log("generating " + process.argv[2]);
  canvas.pngStream().pipe(file);
}