#!/usr/bin/env node

var fs = require("fs"),
    vm = require("vm"),
    commander = require("commander"),
    topojson = require("../");

commander
    .version(require("../package.json").version)
    .usage("[options] <target=source> [file]")
    .description("Merges the source TopoJSON geometry collection, assigning to the target.")
    .option("-o, --out <file>", "output topology file name; defaults to “-” for stdout", "-")
    .option("-k, --key <expression>", "group geometries by key")
    .option("-f, --filter <expression>", "filter merged geometries or meshed lines")
    .option("--mesh", "mesh lines instead of merging polygons")
    .parse(process.argv);

if (commander.args.length < 1) {
  console.error();
  console.error("  error: missing source and target names");
  console.error();
  process.exit(1);
} else if (commander.args.length > 2) {
  console.error();
  console.error("  error: multiple input files");
  console.error();
  process.exit(1);
} else if (commander.args.length === 1) {
  commander.args.push("-");
}

var keyFunction = function() {},
    postfilterFunction = function() { return true; },
    prefilterFunction = function() { return true; };

if (commander.key != null) {
  var keySandbox = {d: undefined, i: -1},
      keyContext = new vm.createContext(keySandbox),
      keyScript = new vm.Script("(" + commander.key + ")");
  keyFunction = function(d, i) {
    keySandbox.d = d;
    keySandbox.i = i;
    return keyScript.runInContext(keyContext);
  };
}

if (commander.filter != null) {
  if (commander.mesh) {
    var filterSandbox = {a: undefined, b: undefined},
        filterContext = new vm.createContext(filterSandbox),
        filterScript = new vm.Script("(" + commander.filter + ")");
    postfilterFunction = function(a, b) {
      filterSandbox.a = a;
      filterSandbox.b = b;
      return filterScript.runInContext(filterContext);
    };
  } else {
    var filterSandbox = {d: undefined, i: -1},
        filterContext = new vm.createContext(filterSandbox),
        filterScript = new vm.Script("(" + commander.filter + ")");
    prefilterFunction = function(d, i) {
      filterSandbox.d = d;
      filterSandbox.i = i;
      return filterScript.runInContext(filterContext);
    };
  }
}

read(commander.args[1]).then(merge).then(write(commander.out)).catch(abort);

function read(file) {
  return new Promise(function(resolve, reject) {
    var data = [], stream = file === "-" ? process.stdin : fs.createReadStream(file);
    stream
        .on("data", function(d) { data.push(d); })
        .on("end", function() { resolve(JSON.parse(Buffer.concat(data))); })
        .on("error", reject);
  });
}

function merge(topology) {
  var name = commander.args[0], i = name.indexOf("="),
      sourceName = i >= 0 ? name.slice(i + 1) : name,
      targetName = i >= 0 ? name.slice(0, i) : name,
      source = topology.objects[sourceName],
      target = topology.objects[targetName] = {type: "GeometryCollection", geometries: []},
      geometries = target.geometries,
      geometriesByKey = {},
      k;

  if (!source) {
    console.error();
    console.error("  error: source object “" + name + "” not found");
    console.error();
    process.exit(1);
  }

  if (source.type !== "GeometryCollection") {
    console.error();
    console.error("  error: expected GeometryCollection, not " + source.type);
    console.error();
    process.exit(1);
  }

  source.geometries.forEach(function(geometry, i) {
    if (!prefilterFunction(geometry, i)) return;
    var k = stringify(keyFunction(geometry, i)), v;
    if (v = geometriesByKey[k]) v.push(geometry);
    else geometriesByKey[k] = v = [geometry];
  });

  if (commander.mesh) {
    for (k in geometriesByKey) {
      var v = geometriesByKey[k],
          o = topojson.meshArcs(topology, {type: "GeometryCollection", geometries: v}, postfilterFunction);
      o.id = k.length > 1 ? k.slice(1) : undefined;
      o.properties = properties(v);
      geometries.push(o);
    }
  } else {
    for (k in geometriesByKey) {
      var v = geometriesByKey[k],
          o = topojson.mergeArcs(topology, v);
      o.id = k.length > 1 ? k.slice(1) : undefined;
      o.properties = properties(v);
      geometries.push(o);
    }
  }

  return topology;
}

function stringify(key) {
  return key == null ? "$" : "$" + key;
}

function properties(objects) {
  var properties = undefined, hasProperties;

  objects.forEach(function(object) {
    var newProperties = object.properties, key;

    // If no properties have yet been merged,
    // then we need to initialize the merged properties object.
    if (properties === undefined) {

      // If the first set of properties is null, undefined or empty,
      // then the result of the merge will be the empty set.
      // Otherwise, the new properties can copied into the merged object.
      if (newProperties != null) for (key in newProperties) {
        properties = {};
        for (key in newProperties) properties[key] = newProperties[key];
        return;
      }

      properties = null;
      return;
    }

    // If any of the new properties are null or undefined,
    // then the result of the merge will be the empty set.
    if (newProperties == null) properties = null;
    if (properties === null) return;

    // Now mark as inconsistent any of the properties
    // that differ from previously-merged values.
    for (key in newProperties) {
      if ((key in properties) && !is(properties[key], newProperties[key])) {
        properties[key] = undefined;
      }
    }

    // And mark as inconsistent any of the properties
    // that are missing from this new set of merged values.
    for (key in properties) {
      if (!(key in newProperties)) {
        properties[key] = undefined;
      }
    }

    return object;
  });

  // Return undefined if there are no properties.
  for (var key in properties) {
    if (properties[key] !== undefined) {
      return properties;
    }
  }
};

function write(file) {
  var stream = (file === "-" ? process.stdout : fs.createWriteStream(file)).on("error", handleEpipe);
  return function(topology) {
    return new Promise(function(resolve, reject) {
      stream.on("error", reject)[stream === process.stdout ? "write" : "end"](JSON.stringify(topology) + "\n", function(error) {
        if (error) reject(error);
        else resolve();
      });
    });
  };
}

function handleEpipe(error) {
  if (error.code === "EPIPE" || error.errno === "EPIPE") {
    process.exit(0);
  }
}

function abort(error) {
  console.error(error.stack);
}

function is(x, y) {
  return x === y ? x !== 0 || 1 / x === 1 / y : x !== x && y !== y;
}