/**
 * (c) 2016 Highsoft AS
 * Author: Øystein Moseng
 *
 * License: www.highcharts.com/license
 */
'use strict';
import H from '../parts/Globals.js';
import '../parts/Utilities.js';

var min = Math.min,
    max = Math.max,
    abs = Math.abs,
    pick = H.pick;

/**
 * Get index of last obstacle before xMin. Employs a type of binary search, and
 * thus requires that obstacles are sorted by xMin value.
 *
 * @param {Array} obstacles Array of obstacles to search in.
 * @param {Number} xMin The xMin threshold.
 * @param {Number} startIx Starting index to search from. Must be within array
 *  range.
 *
 * @return {Number} result The index of the last obstacle element before xMin.
 */
function findLastObstacleBefore(obstacles, xMin, startIx) {
    var left = startIx || 0, // left limit
        right = obstacles.length - 1, // right limit
        min = xMin - 0.0000001, // Make sure we include all obstacles at xMin
        cursor,
        cmp;
    while (left <= right) {
        cursor = (right + left) >> 1;
        cmp = min - obstacles[cursor].xMin;
        if (cmp > 0) {
            left = cursor + 1;
        } else if (cmp < 0) {
            right = cursor - 1;
        } else {
            return cursor;
        }
    }
    return left > 0 ? left - 1 : 0;
}

/**
 * Test if a point lays within an obstacle.
 *
 * @param {Object} obstacle Obstacle to test.
 * @param {Object} point Point with x/y props.
 *
 * @return {Boolean} result Whether point is within the obstacle or not.
 */
function pointWithinObstacle(obstacle, point) {
    return (
        point.x <= obstacle.xMax &&
        point.x >= obstacle.xMin &&
        point.y <= obstacle.yMax &&
        point.y >= obstacle.yMin
    );
}

/**
 * Find the index of an obstacle that wraps around a point.
 * Returns -1 if not found.
 *
 * @param {Array} obstacles Obstacles to test.
 * @param {Object} point Point with x/y props.
 *
 * @return {Number} result Ix of the obstacle in the array, or -1 if not found.
 */
function findObstacleFromPoint(obstacles, point) {
    var i = findLastObstacleBefore(obstacles, point.x + 1) + 1;
    while (i--) {
        if (obstacles[i].xMax >= point.x &&
            // optimization using lazy evaluation
            pointWithinObstacle(obstacles[i], point)) {
            return i;
        }
    }
    return -1;
}

/**
 * Get SVG path array from array of line segments.
 *
 * @param {Array} segments The segments to build the path from.
 *
 * @return {Array} result SVG path array as accepted by the SVG Renderer.
 */
function pathFromSegments(segments) {
    var path = [];
    if (segments.length) {
        path.push('M', segments[0].start.x, segments[0].start.y);
        for (var i = 0; i < segments.length; ++i) {
            path.push('L', segments[i].end.x, segments[i].end.y);
        }
    }
    return path;
}

/**
 * Limits obstacle max/mins in all directions to bounds. Modifies input
 * obstacle.
 *
 * @param {Object} obstacle Obstacle to limit.
 * @param {Object} bounds Bounds to use as limit.
 */
function limitObstacleToBounds(obstacle, bounds) {
    obstacle.yMin = max(obstacle.yMin, bounds.yMin);
    obstacle.yMax = min(obstacle.yMax, bounds.yMax);
    obstacle.xMin = max(obstacle.xMin, bounds.xMin);
    obstacle.xMax = min(obstacle.xMax, bounds.xMax);
}



// Define the available pathfinding algorithms.
// Algorithms take up to 3 arguments: starting point, ending point, and an
// options object.
var algorithms = {

    /**
     * Get an SVG path from a starting coordinate to an ending coordinate.
     * Draws a straight line.
     *
     * @param {Object} start Starting coordinate, object with x/y props.
     * @param {Object} end Ending coordinate, object with x/y props.
     *
     * @return {Object} result An object with the SVG path in Array form as
     *  accepted by the SVG renderer, as well as an array of new obstacles
     *  making up this path.
     */
    straight: function (start, end) {
        return {
            path: ['M', start.x, start.y, 'L', end.x, end.y],
            obstacles: [{ start: start, end: end }]
        };
    },

    /**
     * Find a path from a starting coordinate to an ending coordinate, using
     * right angles only, and taking only starting/ending obstacle into
     * consideration.
     *
     *  Options
     *      - chartObstacles:   Array of chart obstacles to avoid
     *      - startDirectionX:  Optional. True if starting in the X direction.
     *                          If not provided, the algorithm starts in the
     *                          direction that is the furthest between
     *                          start/end.
     *
     * @param {Object} start Starting coordinate, object with x/y props.
     * @param {Object} end Ending coordinate, object with x/y props.
     * @param {Object} options Options for the algorithm.
     *
     * @return {Object} result An object with the SVG path in Array form as
     *  accepted by the SVG renderer, as well as an array of new obstacles
     *  making up this path.
     */
    simpleConnect: H.extend(function (start, end, options) {
        var segments = [],
            endSegment,
            dir = pick(
                options.startDirectionX,
                abs(end.x - start.x) > abs(end.y - start.y)
            ) ? 'x' : 'y',
            chartObstacles = options.chartObstacles,
            startObstacleIx = findObstacleFromPoint(chartObstacles, start),
            endObstacleIx = findObstacleFromPoint(chartObstacles, end),
            startObstacle,
            endObstacle,
            prevWaypoint,
            waypoint,
            waypoint2,
            useMax,
            endPoint;

        // Return a clone of a point with a property set from a target object,
        // optionally with an offset
        function copyFromPoint(from, fromKey, to, toKey, offset) {
            var point = {
                x: from.x,
                y: from.y
            };
            point[fromKey] = to[toKey || fromKey] + (offset || 0);
            return point;
        }

        // Return waypoint outside obstacle
        function getMeOut(obstacle, point, direction) {
            var useMax = abs(point[direction] - obstacle[direction + 'Min']) >
                        abs(point[direction] - obstacle[direction + 'Max']);
            return copyFromPoint(
                point,
                direction,
                obstacle,
                direction + (useMax ? 'Max' : 'Min'),
                useMax ? 1 : -1
            );
        }

        // Pull out end point
        if (endObstacleIx > -1) {
            endObstacle = chartObstacles[endObstacleIx];
            waypoint = getMeOut(endObstacle, end, dir);
            endSegment = {
                start: waypoint,
                end: end
            };
            endPoint = waypoint;
        } else {
            endPoint = end;
        }

        // If an obstacle envelops the start point, add a segment to get out,
        // and around it.
        if (startObstacleIx > -1) {
            startObstacle = chartObstacles[startObstacleIx];
            waypoint = getMeOut(startObstacle, start, dir);
            segments.push({
                start: start,
                end: waypoint
            });

            // If we are going back again, switch direction to get around start
            // obstacle.
            if (
                waypoint[dir] > start[dir] ===  // Going towards max from start
                waypoint[dir] > endPoint[dir]   // Going towards min to end
            ) {
                dir = dir === 'y' ? 'x' : 'y';
                useMax = start[dir] < end[dir];
                segments.push({
                    start: waypoint,
                    end: copyFromPoint(
                        waypoint,
                        dir,
                        startObstacle,
                        dir + (useMax ? 'Max' : 'Min'),
                        useMax ? 1 : -1
                    )
                });

                // Switch direction again
                dir = dir === 'y' ? 'x' : 'y';
            }
        }

        // We are around the start obstacle. Go towards the end in one
        // direction.
        prevWaypoint = segments.length ?
            segments[segments.length - 1].end :
            start;
        waypoint = copyFromPoint(prevWaypoint, dir, endPoint);
        segments.push({
            start: prevWaypoint,
            end: waypoint
        });

        // Final run to end point in the other direction
        dir = dir === 'y' ? 'x' : 'y';
        waypoint2 = copyFromPoint(waypoint, dir, endPoint);
        segments.push({
            start: waypoint,
            end: waypoint2
        });

        // Finally add the endSegment
        segments.push(endSegment);

        return {
            path: pathFromSegments(segments),
            obstacles: segments
        };
    }, {
        requiresObstacles: true
    }),

    /**
     * Find a path from a starting coordinate to an ending coordinate, taking
     * obstacles into consideration. Might not always find the optimal path,
     * but is fast, and usually good enough.
     *
     *  Options
     *      - chartObstacles:   Array of chart obstacles to avoid
     *      - lineObstacles:    Array of line obstacles to jump over
     *      - obstacleMetrics:  Object with metrics of chartObstacles cached
     *      - hardBounds:       Hard boundaries to not cross
     *      - obstacleOptions:  Options for the obstacles, including margin
     *      - startDirectionX:  Optional. True if starting in the X direction.
     *                          If not provided, the algorithm starts in the
     *                          direction that is the furthest between
     *                          start/end.
     *
     * @param {Object} start Starting coordinate, object with x/y props.
     * @param {Object} end Ending coordinate, object with x/y props.
     * @param {Object} options Options for the algorithm.
     *
     * @return {Object} result An object with the SVG path in Array form as
     *  accepted by the SVG renderer, as well as an array of new obstacles
     *  making up this path.
     */
    fastAvoid: H.extend(function (start, end, options) {
        /*
            Algorithm rules/description
            - Find initial direction
            - Determine soft/hard max for each direction.
            - Move along initial direction until obstacle.
            - Change direction.
            - If hitting obstacle, first try to change length of previous line
              before changing direction again.

            Soft min/max x = start/destination x +/- widest obstacle + margin
            Soft min/max y = start/destination y +/- tallest obstacle + margin

            TODO:
                - Make retrospective, try changing prev segment to reduce
                  corners
                - Fix logic for breaking out of end-points - not always picking
                  the best direction currently
                - When going around the end obstacle we should not always go the
                  shortest route, rather pick the one closer to the end point
        */
        var dirIsX = pick(
                options.startDirectionX,
                abs(end.x - start.x) > abs(end.y - start.y)
            ),
            dir = dirIsX ? 'x' : 'y',
            segments,
            useMax,
            extractedEndPoint,
            endSegments = [],
            forceObstacleBreak = false, // Used in clearPathTo to keep track of
                                    // when to force break through an obstacle.

            // Boundaries to stay within. If beyond soft boundary, prefer to
            // change direction ASAP. If at hard max, always change immediately.
            metrics = options.obstacleMetrics,
            softMinX = min(start.x, end.x) - metrics.maxWidth - 10,
            softMaxX = max(start.x, end.x) + metrics.maxWidth + 10,
            softMinY = min(start.y, end.y) - metrics.maxHeight - 10,
            softMaxY = max(start.y, end.y) + metrics.maxHeight + 10,

            // Obstacles
            chartObstacles = options.chartObstacles,
            startObstacleIx = findLastObstacleBefore(chartObstacles, softMinX),
            endObstacleIx = findLastObstacleBefore(chartObstacles, softMaxX);

        // How far can you go between two points before hitting an obstacle?
        // Does not work for diagonal lines (because it doesn't have to).
        function pivotPoint(fromPoint, toPoint, directionIsX) {
            var firstPoint,
                lastPoint,
                highestPoint,
                lowestPoint,
                i,
                searchDirection = fromPoint.x < toPoint.x ? 1 : -1;

            if (fromPoint.x < toPoint.x) {
                firstPoint = fromPoint;
                lastPoint = toPoint;
            } else {
                firstPoint = toPoint;
                lastPoint = fromPoint;
            }

            if (fromPoint.y < toPoint.y) {
                lowestPoint = fromPoint;
                highestPoint = toPoint;
            } else {
                lowestPoint = toPoint;
                highestPoint = fromPoint;
            }

            // Go through obstacle range in reverse if toPoint is before
            // fromPoint in the X-dimension.
            i = searchDirection < 0 ?
                // Searching backwards, start at last obstacle before last point
                min(findLastObstacleBefore(chartObstacles, lastPoint.x),
                    chartObstacles.length - 1) :
                // Forwards. Since we're not sorted by xMax, we have to look
                // at all obstacles.
                0;

            // Go through obstacles in this X range
            while (chartObstacles[i] && (
                searchDirection > 0 && chartObstacles[i].xMin <= lastPoint.x ||
                searchDirection < 0 && chartObstacles[i].xMax >= firstPoint.x
            )) {
                // If this obstacle is between from and to points in a straight
                // line, pivot at the intersection.
                if (
                    chartObstacles[i].xMin <= lastPoint.x &&
                    chartObstacles[i].xMax >= firstPoint.x &&
                    chartObstacles[i].yMin <= highestPoint.y &&
                    chartObstacles[i].yMax >= lowestPoint.y
                ) {
                    if (directionIsX) {
                        return {
                            y: fromPoint.y,
                            x: fromPoint.x < toPoint.x ?
                                chartObstacles[i].xMin - 1 :
                                chartObstacles[i].xMax + 1,
                            obstacle: chartObstacles[i]
                        };
                    }
                    // else ...
                    return {
                        x: fromPoint.x,
                        y: fromPoint.y < toPoint.y ?
                            chartObstacles[i].yMin - 1 :
                            chartObstacles[i].yMax + 1,
                        obstacle: chartObstacles[i]
                    };
                }

                i += searchDirection;
            }

            return toPoint;
        }

        /**
         * Decide in which direction to dodge or get out of an obstacle.
         * Considers desired direction, which way is shortest, soft and hard
         * bounds.
         *
         * Returns a string, either xMin, xMax, yMin or yMax.
         *
         * @param {Object} obstacle Obstacle to dodge/escape.
         * @param {Object} fromPoint Point with x/y props that's
         * dodging/escaping.
         * @param {Object} toPoint Goal point.
         * @param {Boolean} dirIsX Dodge in X dimension.
         * @param {Object} bounds Hard and soft boundaries.
         *
         * @return {Boolean} result Use max or not.
         */
        function getDodgeDirection(
            obstacle,
            fromPoint,
            toPoint,
            dirIsX,
            bounds
        ) {
            var softBounds = bounds.soft,
                hardBounds = bounds.hard,
                dir = dirIsX ? 'x' : 'y',
                toPointMax = { x: fromPoint.x, y: fromPoint.y },
                toPointMin = { x: fromPoint.x, y: fromPoint.y },
                minPivot,
                maxPivot,
                maxOutOfSoftBounds = obstacle[dir + 'Max'] >=
                                    softBounds[dir + 'Max'],
                minOutOfSoftBounds = obstacle[dir + 'Min'] <=
                                    softBounds[dir + 'Min'],
                maxOutOfHardBounds = obstacle[dir + 'Max'] >=
                                    hardBounds[dir + 'Max'],
                minOutOfHardBounds = obstacle[dir + 'Min'] <=
                                    hardBounds[dir + 'Min'],
                // Find out if we should prefer one direction over the other if
                // we can choose freely
                minDistance = abs(obstacle[dir + 'Min'] - fromPoint[dir]),
                maxDistance = abs(obstacle[dir + 'Max'] - fromPoint[dir]),
                // If it's a small difference, pick the one leading towards dest
                // point. Otherwise pick the shortest distance
                useMax = abs(minDistance - maxDistance) < 10 ?
                        fromPoint[dir] < toPoint[dir] :
                        maxDistance < minDistance;

            // Check if we hit any obstacles trying to go around in either
            // direction.
            toPointMin[dir] = obstacle[dir + 'Min'];
            toPointMax[dir] = obstacle[dir + 'Max'];
            minPivot = pivotPoint(fromPoint, toPointMin, dirIsX)[dir] !==
                        toPointMin[dir];
            maxPivot = pivotPoint(fromPoint, toPointMax, dirIsX)[dir] !==
                        toPointMax[dir];
            useMax = minPivot ?
                (maxPivot ? useMax : true) :
                (maxPivot ? false : useMax);

            // useMax now contains our preferred choice, bounds not taken into
            // account. If both or neither direction is out of bounds we want to
            // use this.

            // Deal with soft bounds
            useMax = minOutOfSoftBounds ?
                (maxOutOfSoftBounds ? useMax : true) : // Out on min
                (maxOutOfSoftBounds ? false : useMax); // Not out on min

            // Deal with hard bounds
            useMax = minOutOfHardBounds ?
                (maxOutOfHardBounds ? useMax : true) : // Out on min
                (maxOutOfHardBounds ? false : useMax); // Not out on min

            return useMax;
        }

        // Find a clear path between point
        function clearPathTo(fromPoint, toPoint, dirIsX) {
            // Don't waste time if we've hit goal
            if (fromPoint.x === toPoint.x && fromPoint.y === toPoint.y) {
                return [];
            }

            var dir = dirIsX ? 'x' : 'y',
                pivot,
                segments,
                waypoint,
                waypointUseMax,
                envelopingObstacle,
                secondEnvelopingObstacle,
                envelopWaypoint,
                obstacleMargin = options.obstacleOptions.margin,
                bounds = {
                    soft: {
                        xMin: softMinX,
                        xMax: softMaxX,
                        yMin: softMinY,
                        yMax: softMaxY
                    },
                    hard: options.hardBounds
                };

            // If fromPoint is inside an obstacle we have a problem. Break out
            // by just going to the outside of this obstacle. We prefer to go to
            // the nearest edge in the chosen direction.
            envelopingObstacle =
                findObstacleFromPoint(chartObstacles, fromPoint);
            if (envelopingObstacle > -1) {
                envelopingObstacle = chartObstacles[envelopingObstacle];
                waypointUseMax = getDodgeDirection(
                    envelopingObstacle, fromPoint, toPoint, dirIsX, bounds
                );

                // Cut obstacle to hard bounds to make sure we stay within
                limitObstacleToBounds(envelopingObstacle, options.hardBounds);

                envelopWaypoint = dirIsX ? {
                    y: fromPoint.y,
                    x: envelopingObstacle[waypointUseMax ? 'xMax' : 'xMin'] +
                        (waypointUseMax ? 1 : -1)
                } : {
                    x: fromPoint.x,
                    y: envelopingObstacle[waypointUseMax ? 'yMax' : 'yMin'] +
                        (waypointUseMax ? 1 : -1)
                };

                // If we crashed into another obstacle doing this, we put the
                // waypoint between them instead
                secondEnvelopingObstacle = findObstacleFromPoint(
                    chartObstacles, envelopWaypoint);
                if (secondEnvelopingObstacle > -1) {
                    secondEnvelopingObstacle = chartObstacles[
                        secondEnvelopingObstacle
                    ];

                    // Cut obstacle to hard bounds
                    limitObstacleToBounds(
                        secondEnvelopingObstacle,
                        options.hardBounds
                    );

                    // Modify waypoint to lay between obstacles
                    envelopWaypoint[dir] = waypointUseMax ? max(
                        envelopingObstacle[dir + 'Max'] - obstacleMargin + 1,
                        (
                            secondEnvelopingObstacle[dir + 'Min'] +
                            envelopingObstacle[dir + 'Max']
                        ) / 2
                    ) :
                    min(
                        envelopingObstacle[dir + 'Min'] + obstacleMargin - 1,
                        (
                            secondEnvelopingObstacle[dir + 'Max'] +
                            envelopingObstacle[dir + 'Min']
                        ) / 2
                    );

                    // We are not going anywhere. If this happens for the first
                    // time, do nothing. Otherwise, try to go to the extreme of
                    // the obstacle pair in the current direction.
                    if (fromPoint.x === envelopWaypoint.x &&
                        fromPoint.y === envelopWaypoint.y) {
                        if (forceObstacleBreak) {
                            envelopWaypoint[dir] = waypointUseMax ?
                                max(
                                    envelopingObstacle[dir + 'Max'],
                                    secondEnvelopingObstacle[dir + 'Max']
                                ) + 1 :
                                min(
                                    envelopingObstacle[dir + 'Min'],
                                    secondEnvelopingObstacle[dir + 'Min']
                                ) - 1;
                        }
                        // Toggle on if off, and the opposite
                        forceObstacleBreak = !forceObstacleBreak;
                    } else {
                        // This point is not identical to previous.
                        // Clear break trigger.
                        forceObstacleBreak = false;
                    }
                }

                segments = [{
                    start: fromPoint,
                    end: envelopWaypoint
                }];

            } else { // If not enveloping, use standard pivot calculation

                pivot = pivotPoint(fromPoint, {
                    x: dirIsX ? toPoint.x : fromPoint.x,
                    y: dirIsX ? fromPoint.y : toPoint.y
                }, dirIsX);

                segments = [{
                    start: fromPoint,
                    end: {
                        x: pivot.x,
                        y: pivot.y
                    }
                }];

                // Pivot before goal, use a waypoint to dodge obstacle
                if (pivot[dirIsX ? 'x' : 'y'] !== toPoint[dirIsX ? 'x' : 'y']) {
                    // Find direction of waypoint
                    waypointUseMax = getDodgeDirection(
                        pivot.obstacle, pivot, toPoint, !dirIsX, bounds
                    );

                    // Cut waypoint to hard bounds
                    limitObstacleToBounds(pivot.obstacle, options.hardBounds);

                    waypoint = {
                        x: dirIsX ?
                            pivot.x :
                            pivot.obstacle[waypointUseMax ? 'xMax' : 'xMin'] +
                                (waypointUseMax ? 1 : -1),
                        y: dirIsX ?
                            pivot.obstacle[waypointUseMax ? 'yMax' : 'yMin'] +
                                (waypointUseMax ? 1 : -1) :
                            pivot.y
                    };

                    // We're changing direction here, store that to make sure we
                    // also change direction when adding the last segment array
                    // after handling waypoint.
                    dirIsX = !dirIsX;

                    segments = segments.concat(clearPathTo({
                        x: pivot.x,
                        y: pivot.y
                    }, waypoint, dirIsX));
                }
            }

            // Get segments for the other direction too
            // Recursion is our friend
            segments = segments.concat(clearPathTo(
                segments[segments.length - 1].end, toPoint, !dirIsX
            ));

            return segments;
        }

        // Extract point to outside of obstacle in whichever direction is
        // closest. Returns new point outside obstacle.
        function extractFromObstacle(obstacle, point, goalPoint) {
            var dirIsX = min(obstacle.xMax - point.x, point.x - obstacle.xMin) <
                        min(obstacle.yMax - point.y, point.y - obstacle.yMin),
                bounds = {
                    soft: options.hardBounds,
                    hard: options.hardBounds
                },
                useMax = getDodgeDirection(
                    obstacle, point, goalPoint, dirIsX, bounds
                );

            return dirIsX ? {
                y: point.y,
                x: obstacle[useMax ? 'xMax' : 'xMin'] + (useMax ? 1 : -1)
            } : {
                x: point.x,
                y: obstacle[useMax ? 'yMax' : 'yMin'] + (useMax ? 1 : -1)
            };
        }

        // Cut the obstacle array to soft bounds for optimization in large
        // datasets.
        chartObstacles =
            chartObstacles.slice(startObstacleIx, endObstacleIx + 1);

        // If an obstacle envelops the end point, move it out of there and add
        // a little segment to where it was.
        if ((endObstacleIx = findObstacleFromPoint(chartObstacles, end)) > -1) {
            extractedEndPoint = extractFromObstacle(
                chartObstacles[endObstacleIx],
                end,
                start
            );
            endSegments.push({
                end: end,
                start: extractedEndPoint
            });
            end = extractedEndPoint;
        }
        // If it's still inside one or more obstacles, get out of there by
        // force-moving towards the start point.
        while (
            (endObstacleIx = findObstacleFromPoint(chartObstacles, end)) > -1
        ) {
            useMax = end[dir] - start[dir] < 0;
            extractedEndPoint = {
                x: end.x,
                y: end.y
            };
            extractedEndPoint[dir] = chartObstacles[endObstacleIx][
                useMax ? dir + 'Max' : dir + 'Min'
            ] + (useMax ? 1 : -1);
            endSegments.push({
                end: end,
                start: extractedEndPoint
            });
            end = extractedEndPoint;
        }

        // Find the path
        segments = clearPathTo(start, end, dirIsX);

        // Add the end-point segments
        segments = segments.concat(endSegments.reverse());

        return {
            path: pathFromSegments(segments),
            obstacles: segments
        };
    }, {
        requiresObstacles: true
    })
};

export default algorithms;
