let simulated = false;
let file_version = 2;
let code_key = 47490;

let interests_colors = [
    0x780F, // Bakery, purple
    0x001F, // DrinkingWater, blue
    0x07FF, // Toilets, cyan
    0x7BEF, // BikeShop, dark grey
    0xAFE5, // ChargingStation, green yellow
    0x7800, // Bank, maroon
    0xF800, // Supermarket, red
    0xF81F, // Table, pink
    0xFD20, // Artwork, orange
    0x07E0, // Pharmacy, green
];

function binary_search(array, x) {
    let start = 0, end = array.length - 1;

    while (start <= end){
        let mid = Math.floor((start + end) / 2);
        if (array[mid] < x)
             start = mid + 1;
        else
             end = mid - 1;
    }
    return start;
}

class Status {
    constructor(path) {
        this.path = path;
        this.on_path = false; // are we on the path or lost ?
        this.position = null; // where we are
        this.cos_direction = null; // cos of where we look at
        this.sin_direction = null; // sin of where we look at
        this.current_segment = null; // which segment is closest
        this.reaching = null; // which waypoint are we reaching ?
        this.distance_to_next_point = null; // how far are we from next point ?

        let r = [0];
        // let's do a reversed prefix computations on all distances:
        // loop on all segments in reversed order
        let previous_point = null;
        for (let i = this.path.len - 1; i >= 0; i--) {
            let point = this.path.point(i);
            if (previous_point !== null) {
                r.unshift(r[0] + point.distance(previous_point));
            }
            previous_point = point;
        }
        this.remaining_distances = r; // how much distance remains at start of each segment
    }
    update_position(new_position, direction) {

        if (Bangle.isLocked() && this.position !== null && new_position.lon == this.position.lon && new_position.lat == this.position.lat) {
            return;
        }

        this.cos_direction = Math.cos(-direction - Math.PI / 2.0);
        this.sin_direction = Math.sin(-direction - Math.PI / 2.0);
        this.position = new_position;

        // detect segment we are on now
        let next_segment = this.path.nearest_segment(this.position, Math.max(0, this.current_segment-1), Math.min(this.current_segment+2, this.path.len - 1), this.cos_direction, this.sin_direction);

        if (this.is_lost(next_segment)) {
            // it did not work, try anywhere
            next_segment = this.path.nearest_segment(this.position, 0, this.path.len - 1, this.cos_direction, this.sin_direction);
        }
        // now check if we strayed away from path or back to it
        let lost = this.is_lost(next_segment);
        if (this.on_path == lost) { // if status changes
            if (lost) {
                Bangle.buzz(); // we lost path
                setTimeout(()=>Bangle.buzz(), 500);
            }
            this.on_path = !lost;
        }

        this.current_segment = next_segment;

        // check if we are nearing the next point on our path and alert the user
        let next_point = this.current_segment + 1;
        this.distance_to_next_point = Math.ceil(this.position.distance(this.path.point(next_point)));
        if (this.reaching != next_point && this.distance_to_next_point <= 20) {
            this.reaching = next_point;
            let reaching_waypoint = this.path.is_waypoint(next_point);
            if (reaching_waypoint) {
                Bangle.buzz();
                if (Bangle.isLocked()) {
                    Bangle.setLocked(false);
                }
            }
        }
        // re-display unless locked
        if (!Bangle.isLocked() || simulated) {
            this.display();
        }
    }
    remaining_distance() {
        return this.remaining_distances[this.current_segment+1] + this.position.distance(this.path.point(this.current_segment+1));
    }
    is_lost(segment) {
        let distance_to_nearest = this.position.fake_distance_to_segment(this.path.point(segment), this.path.point(segment+1));
        let meters = 6371e3 * distance_to_nearest;
        return (meters > 20);
    }
    display() {
        g.clear();
        this.display_map();
        this.display_interest_points();
        this.display_stats();
        Bangle.drawWidgets();
    }
    display_interest_points() {
        // this is the algorithm in case we have a lot of interest points
        // let's draw all points for 5 segments centered on current one
        let starting_group = Math.floor(Math.max(this.current_segment-2, 0) / 3);
        let ending_group = Math.floor(Math.min(this.current_segment+2, this.path.len-2) / 3);
        let starting_bucket = binary_search(this.path.interests_starts, starting_group);
        let ending_bucket = binary_search(this.path.interests_starts, ending_group+0.5);
        // we have 5 points per bucket
        let end_index = Math.min(this.path.interests_types.length - 1, ending_bucket*5);
        for (let i = starting_bucket*5 ; i <= end_index ; i++) {
            let index = this.path.interests_on_path[i];
            let interest_point = this.path.interest_point(index);
            let color = this.path.interest_color(i);
            let c = interest_point.coordinates(this.position, this.cos_direction, this.sin_direction);
            g.setColor(color).fillCircle(c[0], c[1], 5);
        }
    }
    display_stats() {
        let rounded_distance = Math.round(this.remaining_distance() / 100) / 10;
        let total = Math.round(this.remaining_distances[0] / 100) / 10;
        let now = new Date();
        let minutes = now.getMinutes().toString();
        if (minutes.length < 2) {
            minutes = '0' + minutes;
        }
        let hours = now.getHours().toString();
        g.setFont("6x8:2").setColor(g.theme.fg).drawString(hours + ":" + minutes, 0, g.getHeight() - 49);
        g.drawString("d. " + rounded_distance + "/" + total, 0, g.getHeight() - 32);
        g.drawString("seg." + (this.current_segment + 1) + "/" + this.path.len + "  " + this.distance_to_next_point + "m", 0, g.getHeight() - 15);
    }
    display_map() {
        // don't display all segments, only those neighbouring current segment
        // this is most likely to be the correct display
        // while lowering the cost a lot
        //
        // note that all code is inlined here to speed things up from 400ms to 200ms
        let start = Math.max(this.current_segment - 3, 0);
        let end = Math.min(this.current_segment + 5, this.path.len - 1);
        let pos = this.position;
        let cos = this.cos_direction;
        let sin = this.sin_direction;
        let points = this.path.points;
        let cx = pos.lon;
        let cy = pos.lat;
        let half_width = g.getWidth() / 2;
        let half_height = g.getHeight() / 2;
        let previous_x = null;
        let previous_y = null;
        for (let i = start ; i < end ; i++) {
            let tx = (points[2*i] - cx) * 40000.0;
            let ty = (points[2*i+1] - cy) * 40000.0;
            let rotated_x = tx * cos - ty * sin;
            let rotated_y = tx * sin + ty * cos;
            let x = half_width - Math.round(rotated_x); // x is inverted
            let y = half_height + Math.round(rotated_y);
            if (previous_x !== null) {
                if (i == this.current_segment + 1) {
                    g.setColor(0.0, 1.0, 0.0);
                } else {
                    g.setColor(1.0, 0.0, 0.0);
                }
                g.drawLine(previous_x, previous_y, x, y);
            }

            if (this.path.is_waypoint(i-1)) {
                g.setColor(g.theme.fg);
                g.fillCircle(previous_x, previous_y, 6);
                g.setColor(g.theme.bg);
                g.fillCircle(previous_x, previous_y, 5);
            }
            g.setColor(g.theme.fg);
            g.fillCircle(previous_x, previous_y, 4);
            g.setColor(g.theme.bg);
            g.fillCircle(previous_x, previous_y, 3);

            previous_x = x;
            previous_y = y;
        }

        if (this.path.is_waypoint(end-1)) {
            g.setColor(g.theme.fg);
            g.fillCircle(previous_x, previous_y, 6);
            g.setColor(g.theme.bg);
            g.fillCircle(previous_x, previous_y, 5);
        }
        g.setColor(g.theme.fg);
        g.fillCircle(previous_x, previous_y, 4);
        g.setColor(g.theme.bg);
        g.fillCircle(previous_x, previous_y, 3);

        // now display ourselves
        g.setColor(g.theme.fgH);
        g.fillCircle(half_width, half_height, 5);
    }
}

class Path {
    constructor(filename) {
        let buffer = require("Storage").readArrayBuffer(filename);
        let offset = 0;

        // header
        let header = Uint16Array(buffer, offset, 5);
        offset += 5 * 2;
        let key = header[0];
        let version = header[1];
        let points_number = header[2];
        if ((key != code_key)||(version>file_version)) {
            E.showMessage("Invalid gpc file");
            return;
        }

        // path points
        this.points = Float64Array(buffer, offset, points_number*2);

        // interest points
        offset += 8 * points_number * 2;
        let interests_number = header[3];
        this.interests_coordinates = Float64Array(buffer, offset, interests_number * 2);
        offset += 8 * interests_number * 2;
        this.interests_types = Uint8Array(buffer, offset, interests_number);
        offset += interests_number;

        // interests on path
        let interests_on_path_number = header[4];
        this.interests_on_path = Uint16Array(buffer, offset, interests_on_path_number);
        offset += 2 * interests_on_path_number;
        let starts_length = Math.ceil(interests_on_path_number / 5.0);
        this.interests_starts = Uint16Array(buffer, offset, starts_length);
        offset += 2 * starts_length;
    }

    // if start, end or steep direction change
    // we are buzzing and displayed specially
    is_waypoint(point_index) {
        if ((point_index == 0)||(point_index == this.len -1)) {
            return true;
        } else {
            let p1 = this.point(point_index-1);
            let p2 = this.point(point_index);
            let p3 = this.point(point_index+1);
            let d1 = p2.minus(p1);
            let d2 = p3.minus(p2);
            let a1 = Math.atan2(d1.lat, d1.lon);
            let a2 = Math.atan2(d2.lat, d2.lon);
            let direction_change = Math.abs(a2-a1);
            return ((direction_change > Math.PI / 3.0)&&(direction_change < Math.PI * 5.0/3.0));
        }
    }

    // execute op on all segments.
    // start is index of first wanted segment
    // end is 1 after index of last wanted segment
    on_segments(op, start, end) {
        let previous_point = null;
        for (let i = start; i < end + 1; i++) {
            let point = new Point(this.points[2 * i], this.points[2 * i + 1]);
            if (previous_point !== null) {
                op(previous_point, point, i);
            }
            previous_point = point;
        }
    }

    // return point at given index
    point(index) {
        let lon = this.points[2 * index];
        let lat = this.points[2 * index + 1];
        return new Point(lon, lat);
    }

    interest_point(index) {
        let lon = this.interests_coordinates[2 * index];
        let lat = this.interests_coordinates[2 * index + 1];
        return new Point(lon, lat);
    }

    interest_color(index) {
        return interests_colors[this.interests_types[index]];
    }

    // return index of segment which is nearest from point.
    // we need a direction because we need there is an ambiguity
    // for overlapping segments which are taken once to go and once to come back.
    // (in the other direction).
    nearest_segment(point, start, end, cos_direction, sin_direction) {
        // we are going to compute two min distances, one for each direction.
        let indices = [0, 0];
        let mins = [Number.MAX_VALUE, Number.MAX_VALUE];
        this.on_segments(function(p1, p2, i) {
            // we use the dot product to figure out if oriented correctly
            let distance = point.fake_distance_to_segment(p1, p2);
            let diff = p2.minus(p1);
            let dot = cos_direction * diff.lon + sin_direction * diff.lat;
            let orientation = + (dot < 0); // index 0 is good orientation
            if (distance <= mins[orientation]) {
                mins[orientation] = distance;
                indices[orientation] = i - 1;
            }
        }, start, end);
        // by default correct orientation (0) wins
        // but if other one is really closer, return other one
        if (mins[1] < mins[0] / 10.0) {
            return indices[1];
        } else {
            return indices[0];
        }
    }
    get len() {
        return this.points.length / 2;
    }
}

class Point {
    constructor(lon, lat) {
        this.lon = lon;
        this.lat = lat;
    }
    coordinates(current_position, cos_direction, sin_direction) {
        let translated = this.minus(current_position).times(40000.0);
        let rotated_x = translated.lon * cos_direction - translated.lat * sin_direction;
        let rotated_y = translated.lon * sin_direction + translated.lat * cos_direction;
        return [
            g.getWidth() / 2 - Math.round(rotated_x), // x is inverted
            g.getHeight() / 2 + Math.round(rotated_y)
        ];
    }
    minus(other_point) {
        let xdiff = this.lon - other_point.lon;
        let ydiff = this.lat - other_point.lat;
        return new Point(xdiff, ydiff);
    }
    plus(other_point) {
        return new Point(this.lon + other_point.lon, this.lat + other_point.lat);
    }
    length_squared(other_point) {
        let d = this.minus(other_point);
        return (d.lon * d.lon + d.lat * d.lat);
    }
    times(scalar) {
        return new Point(this.lon * scalar, this.lat * scalar);
    }
    dot(other_point) {
        return this.lon * other_point.lon + this.lat * other_point.lat;
    }
    distance(other_point) {
        //see https://www.movable-type.co.uk/scripts/latlong.html
        const R = 6371e3; // metres
        const phi1 = this.lat * Math.PI / 180;
        const phi2 = other_point.lat * Math.PI / 180;
        const deltaphi = (other_point.lat - this.lat) * Math.PI / 180;
        const deltalambda = (other_point.lon - this.lon) * Math.PI / 180;

        const a = Math.sin(deltaphi / 2) * Math.sin(deltaphi / 2) +
            Math.cos(phi1) * Math.cos(phi2) *
            Math.sin(deltalambda / 2) * Math.sin(deltalambda / 2);
        const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

        return R * c; // in metres
    }
    fake_distance(other_point) {
        return Math.sqrt(this.length_squared(other_point));
    }
    fake_distance_to_segment(v, w) {
        // from : https://stackoverflow.com/questions/849211/shortest-distance-between-a-point-and-a-line-segment
        // Return minimum distance between line segment vw and point p
        let l2 = v.length_squared(w); // i.e. |w-v|^2 -  avoid a sqrt
        if (l2 == 0.0) {
            return this.distance(v); // v == w case
        }
        // Consider the line extending the segment, parameterized as v + t (w - v).
        // We find projection of point p onto the line.
        // It falls where t = [(p-v) . (w-v)] / |w-v|^2
        // We clamp t from [0,1] to handle points outside the segment vw.
        let t = Math.max(0, Math.min(1, (this.minus(v)).dot(w.minus(v)) / l2));

        let projection = v.plus((w.minus(v)).times(t)); // Projection falls on the segment
        return this.fake_distance(projection);
    }
}


Bangle.loadWidgets();


let fake_gps_point = 0.0;
function simulate_gps(status) {
    if (fake_gps_point > status.path.len -1) {
        return;
    }
    let point_index = Math.floor(fake_gps_point);
    if (point_index >= status.path.len) {
        return;
    }
    let p1 = status.path.point(point_index);
    let p2 = status.path.point(point_index + 1);

    let alpha = fake_gps_point - point_index;
    let pos = p1.times(1-alpha).plus(p2.times(alpha));
    let old_pos = status.position;

    fake_gps_point += 0.2; // advance simulation
    let direction = Math.atan2(pos.lat - old_pos.lat, pos.lon - old_pos.lon);
    status.update_position(pos, direction);
}

function drawMenu() {
  const menu = {
    '': { 'title': 'choose trace' }
  };
  var files = require("Storage").list(".gpc");
  for (var i=0; i<files.length; ++i) {
    menu[files[i]] = start.bind(null, files[i]);
  }
  menu['Exit'] = function() { load(); };
  E.showMenu(menu);
}



function start(fn) {
    console.log("loading", fn);

    let path = new Path(fn);
    let status = new Status(path);

    if (simulated) {
      status.position = new Point(status.path.point(0));
      setInterval(simulate_gps, 500, status);
    } else {
      // let's display start while waiting for gps signal
      let p1 = status.path.point(0);
      let p2 = status.path.point(1);
      let diff = p2.minus(p1);
      let direction = Math.atan2(diff.lat, diff.lon);
      Bangle.setLocked(false);
      status.update_position(p1, direction);

      let frame = 0;
      let old_points = []; // remember the at most 3 previous points
      let set_coordinates = function(data) {
          frame += 1;
          let valid_coordinates = !isNaN(data.lat) && !isNaN(data.lon);
          if (valid_coordinates) {
              // we try to figure out direction by looking at previous points
              // instead of the gps course which is not very nice.
              let direction = data.course * Math.PI / 180.0;
              let position = new Point(data.lon, data.lat);
              if (old_points.length == 0) {
                  old_points.push(position);
              } else {
                  let last_point = old_points[old_points.length-1];
                  if (last_point.x != position.x || last_point.y != position.y) {
                      if (old_points.length == 4) {
                          old_points.shift();
                      }
                      old_points.push(position);
                  }
              }
              if (old_points.length == 4) {
                  // let's just take average angle of 3 previous segments
                  let angles_sum = 0;
                  for(let i = 0 ; i < 3 ; i++) {
                      let p1 = old_points[i];
                      let p2 = old_points[i+1];
                      let diff = p2.minus(p1);
                      let angle = Math.atan2(diff.lat, diff.lon);
                      angles_sum += angle;
                  }
                  status.update_position(position, angles_sum / 3.0);
              } else {
                  status.update_position(position, direction);
              }
          }
          let gps_status_color;
          if ((frame % 2 == 0)||valid_coordinates) {
              gps_status_color = g.theme.bg;
          } else {
              gps_status_color = g.theme.fg;
          }
          g.setColor(gps_status_color).setFont("6x8:2").drawString("gps", g.getWidth() - 40, 30);
      }

      Bangle.setGPSPower(true, "gipy");
      Bangle.on('GPS', set_coordinates);
    }
}

let files = require("Storage").list(".gpc");
if (files.length <= 1) {
    if (files.length == 0) {
        load();
    } else {
        start(files[0]);
    }
} else {
    drawMenu();
}