'use strict';
var Cesium = require('cesium');
var path = require('path');
var Promise = require('bluebird');

var ArrayStorage = require('./ArrayStorage');
var loadMtl = require('./loadMtl');
var outsideDirectory = require('./outsideDirectory');
var readLines = require('./readLines');

var Cartesian2 = Cesium.Cartesian2;
var Cartesian3 = Cesium.Cartesian3;
var ComponentDatatype = Cesium.ComponentDatatype;
var defaultValue = Cesium.defaultValue;
var defined = Cesium.defined;
var IntersectionTests = Cesium.IntersectionTests;
var Matrix3 = Cesium.Matrix3;
var OrientedBoundingBox = Cesium.OrientedBoundingBox;
var Plane = Cesium.Plane;
var PolygonPipeline = Cesium.PolygonPipeline;
var Ray = Cesium.Ray;
var RuntimeError = Cesium.RuntimeError;
var WindingOrder = Cesium.WindingOrder;

module.exports = loadObj;

// Object name (o) -> node
// Group name (g) -> mesh
// Material name (usemtl) -> primitive

function Node() {
    this.name = undefined;
    this.meshes = [];
}

function Mesh() {
    this.name = undefined;
    this.primitives = [];
    this.positions = new ArrayStorage(ComponentDatatype.FLOAT);
    this.normals = new ArrayStorage(ComponentDatatype.FLOAT);
    this.uvs = new ArrayStorage(ComponentDatatype.FLOAT);
}

function Primitive() {
    this.material = undefined;
    this.indices = new ArrayStorage(ComponentDatatype.UNSIGNED_INT);
}

// OBJ regex patterns are modified from ThreeJS (https://github.com/mrdoob/three.js/blob/master/examples/js/loaders/OBJLoader.js)
var vertexPattern = /v( +[\d|\.|\+|\-|e|E]+)( +[\d|\.|\+|\-|e|E]+)( +[\d|\.|\+|\-|e|E]+)/;     // v float float float
var normalPattern = /vn( +[\d|\.|\+|\-|e|E]+)( +[\d|\.|\+|\-|e|E]+)( +[\d|\.|\+|\-|e|E]+)/;    // vn float float float
var uvPattern = /vt( +[\d|\.|\+|\-|e|E]+)( +[\d|\.|\+|\-|e|E]+)/;                              // vt float float
var facePattern = /(-?\d+)\/?(-?\d*)\/?(-?\d*)/g;                                              // for any face format "f v", "f v/v", "f v//v", "f v/v/v"

/**
 * Parse an obj file.
 *
 * @param {String} objPath Path to the obj file.
 * @param {Object} options The options object passed along from lib/obj2gltf.js
 * @returns {Promise} A promise resolving to the obj data, which includes an array of nodes containing geometry information and an array of materials.
 *
 * @private
 */
function loadObj(objPath, options) {
    // Global store of vertex attributes listed in the obj file
    var positions = new ArrayStorage(ComponentDatatype.FLOAT);
    var normals = new ArrayStorage(ComponentDatatype.FLOAT);
    var uvs = new ArrayStorage(ComponentDatatype.FLOAT);

    // The current node, mesh, and primitive
    var node;
    var mesh;
    var primitive;
    var activeMaterial;

    // All nodes seen in the obj
    var nodes = [];

    // Used to build the indices. The vertex cache is unique to each mesh.
    var vertexCache = {};
    var vertexCacheLimit = 1000000;
    var vertexCacheCount = 0;
    var vertexCount = 0;

    // All mtl paths seen in the obj
    var mtlPaths = [];

    // Buffers for face data that spans multiple lines
    var lineBuffer = '';

    // Used for parsing face data
    var faceVertices = [];
    var facePositions = [];
    var faceUvs = [];
    var faceNormals = [];

    var vertexIndices = [];

    function getName(name) {
        return (name === '' ? undefined : name);
    }

    function addNode(name) {
        node = new Node();
        node.name = getName(name);
        nodes.push(node);
        addMesh();
    }

    function addMesh(name) {
        mesh = new Mesh();
        mesh.name = getName(name);
        node.meshes.push(mesh);
        addPrimitive();

        // Clear the vertex cache for each new mesh
        vertexCache = {};
        vertexCacheCount = 0;
        vertexCount = 0;
    }

    function addPrimitive() {
        primitive = new Primitive();
        primitive.material = activeMaterial;
        mesh.primitives.push(primitive);
    }

    function useMaterial(name) {
        var material = getName(name);
        activeMaterial = material;

        // Look to see if this material has already been used by a primitive in the mesh
        var primitives = mesh.primitives;
        var primitivesLength = primitives.length;
        for (var i = 0; i < primitivesLength; ++i) {
            if (primitives[i].material === material) {
                primitive = primitives[i];
                return;
            }
        }
        // Add a new primitive with this material
        addPrimitive();
    }

    function getOffset(a, attributeData, components) {
        var i = parseInt(a);
        if (i < 0) {
            // Negative vertex indexes reference the vertices immediately above it
            return (attributeData.length / components + i) * components;
        }
        return (i - 1) * components;
    }

    function createVertex(p, u, n) {
        // Positions
        if (p.length > 0) {
            var pi = getOffset(p, positions, 3);
            var px = positions.get(pi + 0);
            var py = positions.get(pi + 1);
            var pz = positions.get(pi + 2);
            mesh.positions.push(px);
            mesh.positions.push(py);
            mesh.positions.push(pz);
        }

        // Normals
        if (n.length > 0) {
            var ni = getOffset(n, normals, 3);
            var nx = normals.get(ni + 0);
            var ny = normals.get(ni + 1);
            var nz = normals.get(ni + 2);
            mesh.normals.push(nx);
            mesh.normals.push(ny);
            mesh.normals.push(nz);
        }

        // UVs
        if (u.length > 0) {
            var ui = getOffset(u, uvs, 2);
            var ux = uvs.get(ui + 0);
            var uy = uvs.get(ui + 1);
            mesh.uvs.push(ux);
            mesh.uvs.push(uy);
        }
    }

    function addVertex(v, p, u, n) {
        var index = vertexCache[v];
        if (!defined(index)) {
            index = vertexCount++;
            vertexCache[v] = index;
            createVertex(p, u, n);

            // Prevent the vertex cache from growing too large. As a result of clearing the cache there
            // may be some duplicate vertices.
            vertexCacheCount++;
            if (vertexCacheCount > vertexCacheLimit) {
                vertexCacheCount = 0;
                vertexCache = {};
            }
        }
        return index;
    }

    // Given a set of 3D points, project them onto whichever axis will produce the least distortion.
    var scratchIntersectionPoint = new Cartesian3();
    var scratchXAxis = new Cartesian3();
    var scratchYAxis = new Cartesian3();
    var scratchZAxis = new Cartesian3();
    var scratchOrigin = new Cartesian3();
    var scratchNormal = new Cartesian3();
    var scratchRay = new Ray();
    var scratchPlane = new Plane(Cesium.Cartesian3.UNIT_X, 0);
    var scratchPositions2D = [new Cartesian2(), new Cartesian2(), new Cartesian2()];
    function projectTo2D(positions) {
        var positions2D = [];
        var obb = OrientedBoundingBox.fromPoints(positions);
        var halfAxes = obb.halfAxes;
        Matrix3.getColumn(halfAxes, 0, scratchXAxis);
        Matrix3.getColumn(halfAxes, 1, scratchYAxis);
        Matrix3.getColumn(halfAxes, 2, scratchZAxis);

        var xMag = Cartesian3.magnitude(scratchXAxis);
        var yMag = Cartesian3.magnitude(scratchYAxis);
        var zMag = Cartesian3.magnitude(scratchZAxis);
        var min = Math.min(xMag, yMag, zMag);

        var i;
        // If all the points are on a line, just remove one of the zero dimensions
        if (xMag === 0 && (yMag === 0 || zMag === 0)) {
            for (i = 0; i < positions.length; i++) {
                if (i === scratchPositions2D.length) {
                    scratchPositions2D.push(new Cartesian2());
                }
                positions2D[i] = new Cartesian2.fromElements(positions[i].y, positions[i].z, scratchPositions2D[i]);
            }
            return positions2D;
        } else if (yMag === 0 && zMag === 0) {
            for (i = 0; i < positions.length; i++) {
                if (i === scratchPositions2D.length) {
                    scratchPositions2D.push(new Cartesian2());
                }
                positions2D[i] = new Cartesian2.fromElements(positions[i].x, positions[i].y, scratchPositions2D[i]);
            }
            return positions2D;
        }

        var center = obb.center;
        var planeXAxis;
        var planeYAxis;
        if (min === xMag) {
            if (!scratchXAxis.equals(Cartesian3.ZERO)) {
                Cartesian3.add(center, scratchXAxis, scratchOrigin);
                Cartesian3.normalize(scratchXAxis, scratchNormal);
            }
            planeXAxis = Cartesian3.normalize(scratchYAxis, scratchYAxis);
            planeYAxis = Cartesian3.normalize(scratchZAxis, scratchZAxis);
        } else if (min === yMag) {
            if (!scratchYAxis.equals(Cartesian3.ZERO)) {
                Cartesian3.add(center, scratchYAxis, scratchOrigin);
                Cartesian3.normalize(scratchYAxis, scratchNormal);
            }
            planeXAxis = Cartesian3.normalize(scratchXAxis, scratchXAxis);
            planeYAxis = Cartesian3.normalize(scratchZAxis, scratchZAxis);
        } else {
            if (!scratchZAxis.equals(Cartesian3.ZERO)) {
                Cartesian3.add(center, scratchZAxis, scratchOrigin);
                Cartesian3.normalize(scratchZAxis, scratchNormal);
            }
            planeXAxis = Cartesian3.normalize(scratchXAxis, scratchXAxis);
            planeYAxis = Cartesian3.normalize(scratchYAxis, scratchYAxis);
        }

        if (min === 0) {
            scratchNormal = Cartesian3.cross(planeXAxis, planeYAxis, scratchNormal);
            scratchNormal = Cartesian3.normalize(scratchNormal, scratchNormal);
        }

        Plane.fromPointNormal(scratchOrigin, scratchNormal, scratchPlane);
        scratchRay.direction = scratchNormal;

        for (i = 0; i < positions.length; i++) {
            scratchRay.origin = positions[i];

            var intersectionPoint = IntersectionTests.rayPlane(scratchRay, scratchPlane, scratchIntersectionPoint);

            if (!defined(intersectionPoint)) {
                Cartesian3.negate(scratchRay.direction, scratchRay.direction);
                intersectionPoint = IntersectionTests.rayPlane(scratchRay, scratchPlane, scratchIntersectionPoint);
            }
            var v = Cartesian3.subtract(intersectionPoint, scratchOrigin, intersectionPoint);
            var x = Cartesian3.dot(planeXAxis, v);
            var y = Cartesian3.dot(planeYAxis, v);

            if (i === scratchPositions2D.length) {
                scratchPositions2D.push(new Cartesian2());
            }

            positions2D[i] = new Cartesian2.fromElements(x, y, scratchPositions2D[i]);
        }

        return positions2D;
    }

    function get3DPoint(index, result) {
        var pi = getOffset(index, positions, 3);
        var px = positions.get(pi + 0);
        var py = positions.get(pi + 1);
        var pz = positions.get(pi + 2);
        return Cartesian3.fromElements(px, py, pz, result);
    }

    function get3DNormal(index, result) {
        var ni = getOffset(index, normals, 3);
        var nx = normals.get(ni + 0);
        var ny = normals.get(ni + 1);
        var nz = normals.get(ni + 2);
        return Cartesian3.fromElements(nx, ny, nz, result);
    }

    // Given a sequence of three points A B C, determine whether vector BC
    // "turns" clockwise (positive) or counter-clockwise (negative) from vector AB
    var scratch1 = new Cartesian3();
    var scratch2 = new Cartesian3();
    function getTurnDirection(pointA, pointB, pointC) {
        var vector1 = Cartesian2.subtract(pointA, pointB, scratch1);
        var vector2 = Cartesian2.subtract(pointC, pointB, scratch2);
        return vector1.x * vector2.y - vector1.y * vector2.x;
    }

    // Given the cartesian 2 vertices of a polygon, determine if convex
    function isConvex(positions2D) {
        var turnDirection = getTurnDirection(positions2D[0], positions2D[1], positions2D[2]);
        for (var i=1; i < positions2D.length-2; ++i) {
            var currentTurnDirection = getTurnDirection(positions2D[i], positions2D[i+1], positions2D[i+2]);
            if (turnDirection * currentTurnDirection < 0) {
                return false;
            }
        }
        return true;
    }

    var scratch3 = new Cartesian3();
    var scratch4 = new Cartesian3();
    var scratch5 = new Cartesian3();
    // Checks if winding order matches the given normal.
    function checkWindingCorrect(positionIndex1, positionIndex2, positionIndex3, normal) {
        var A = get3DPoint(positionIndex1, scratch1);
        var B = get3DPoint(positionIndex2, scratch2);
        var C = get3DPoint(positionIndex3, scratch3);

        var BA = Cartesian3.subtract(B, A, scratch4);
        var CA = Cartesian3.subtract(C, A, scratch5);
        var cross = Cartesian3.cross(BA, CA, scratch3);

        return (Cartesian3.dot(normal, cross) >= 0);
    }

    function addTriangle(index1, index2, index3, correctWinding) {
        if (correctWinding) {
            primitive.indices.push(index1);
            primitive.indices.push(index2);
            primitive.indices.push(index3);
        } else {
            primitive.indices.push(index1);
            primitive.indices.push(index3);
            primitive.indices.push(index2);
        }
    }

    var scratchPositions3D = [new Cartesian3(), new Cartesian3(), new Cartesian3()];
    function addFace(vertices, positions, uvs, normals) {
        var isWindingCorrect = true;
        var faceNormal;

        // If normals are defined, find a face normal to use in winding order sanitization.
        // If no face normal, we have to assume the winding is correct.
        if (normals[0].length > 0) {
            faceNormal = get3DNormal(normals[0], scratchNormal);
            isWindingCorrect = checkWindingCorrect(positions[0], positions[1], positions[2], faceNormal);
        }

        if (vertices.length === 3) {
            var index1 = addVertex(vertices[0], positions[0], uvs[0], normals[0]);
            var index2 = addVertex(vertices[1], positions[1], uvs[1], normals[1]);
            var index3 = addVertex(vertices[2], positions[2], uvs[2], normals[2]);
            addTriangle(index1, index2, index3, isWindingCorrect);
        } else { // Triangulate if the face is not a triangle
            var positions3D = [];
            vertexIndices.length = 0;

            var i;
            for (i = 0; i < vertices.length; ++i) {
                var index = addVertex(vertices[i], positions[i], uvs[i], normals[i]);
                vertexIndices.push(index);

                // Collect the vertex positions as 3D points
                if (i === scratchPositions3D.length) {
                    scratchPositions3D.push(new Cartesian3());
                }
                positions3D.push(get3DPoint(positions[i], scratchPositions3D[i]));
            }

            var positions2D = projectTo2D(positions3D);

            if (isConvex(positions2D)) {
                for (i=1; i < vertices.length-1; ++i) {
                    addTriangle(vertexIndices[0], vertexIndices[i], vertexIndices[i+1], isWindingCorrect);
                }
            } else {
                // Since the projection doesn't preserve winding order, reverse the order of
                // the vertices before triangulating to enforce counter clockwise.
                var projectedWindingOrder = PolygonPipeline.computeWindingOrder2D(positions2D);
                if (projectedWindingOrder === WindingOrder.CLOCKWISE) {
                    positions2D.reverse();
                }

                // Use an ear-clipping algorithm to triangulate
                var positionIndices = PolygonPipeline.triangulate(positions2D);
                for (i = 0; i < positionIndices.length-2; i += 3) {
                    addTriangle(vertexIndices[positionIndices[i]], vertexIndices[positionIndices[i+1]], vertexIndices[positionIndices[i+2]], isWindingCorrect);
                }
            }
        }
    }

    function parseLine(line) {
        line = line.trim();
        var result;

        if ((line.length === 0) || (line.charAt(0) === '#')) {
            // Don't process empty lines or comments
        } else if (/^o\s/i.test(line)) {
            var objectName = line.substring(2).trim();
            addNode(objectName);
        } else if (/^g\s/i.test(line)) {
            var groupName = line.substring(2).trim();
            addMesh(groupName);
        } else if (/^usemtl\s/i.test(line)) {
            var materialName = line.substring(7).trim();
            useMaterial(materialName);
        } else if (/^mtllib/i.test(line)) {
            var mtllibLine = line.substring(7).trim();
            mtlPaths = mtlPaths.concat(getMtlPaths(mtllibLine));
        } else if ((result = vertexPattern.exec(line)) !== null) {
            positions.push(parseFloat(result[1]));
            positions.push(parseFloat(result[2]));
            positions.push(parseFloat(result[3]));
        } else if ((result = normalPattern.exec(line) ) !== null) {
            var normal = Cartesian3.fromElements(parseFloat(result[1]), parseFloat(result[2]), parseFloat(result[3]), scratchNormal);
            if (Cartesian3.equals(normal, Cartesian3.ZERO)) {
                Cartesian3.clone(Cartesian3.UNIT_Z, normal);
            } else {
                Cartesian3.normalize(normal, normal);
            }
            normals.push(normal.x);
            normals.push(normal.y);
            normals.push(normal.z);
        } else if ((result = uvPattern.exec(line)) !== null) {
            uvs.push(parseFloat(result[1]));
            uvs.push(1.0 - parseFloat(result[2])); // Flip y so 0.0 is the bottom of the image
        } else { // face line or invalid line
            // Because face lines can contain n vertices, we use a line buffer in case the face data spans multiple lines.
            // If there's a line continuation don't create face yet
            if (line.slice(-1) === '\\') {
                lineBuffer += line.substring(0, line.length-1);
                return;
            }
            lineBuffer += line;
            if (lineBuffer.substring(0, 2) === 'f ') {
                while ((result = facePattern.exec(lineBuffer)) !== null) {
                    faceVertices.push(result[0]);
                    facePositions.push(result[1]);
                    faceUvs.push(result[2]);
                    faceNormals.push(result[3]);
                }
                if (faceVertices.length > 2) {
                    addFace(faceVertices, facePositions, faceUvs, faceNormals);
                }

                faceVertices.length = 0;
                facePositions.length = 0;
                faceNormals.length = 0;
                faceUvs.length = 0;
            }
            lineBuffer = '';
        }
    }

    // Create a default node in case there are no o/g/usemtl lines in the obj
    addNode();

    // Parse the obj file
    return readLines(objPath, parseLine)
        .then(function() {
            // Add hasNormals to options object for loadMtl
            options.hasNormals = normals.length > 0;

            // Unload resources
            positions = undefined;
            normals = undefined;
            uvs = undefined;

            // Load materials and textures
            return finishLoading(nodes, mtlPaths, objPath, options);
        });
}

function getMtlPaths(mtllibLine) {
    // Handle paths with spaces. E.g. mtllib my material file.mtl
    var mtlPaths = [];
    var splits = mtllibLine.split(' ');
    var length = splits.length;
    var startIndex = 0;
    for (var i = 0; i < length; ++i) {
        if (path.extname(splits[i]) !== '.mtl') {
            continue;
        }
        var mtlPath = splits.slice(startIndex, i + 1).join(' ');
        mtlPaths.push(mtlPath);
        startIndex = i + 1;
    }
    return mtlPaths;
}

function finishLoading(nodes, mtlPaths, objPath, options) {
    nodes = cleanNodes(nodes);
    if (nodes.length === 0) {
        throw new RuntimeError(objPath + ' does not have any geometry data');
    }
    var name = path.basename(objPath, path.extname(objPath));
    return loadMtls(mtlPaths, objPath, options)
        .then(function(materials) {
            assignDefaultMaterial(nodes, materials);
            return {
                nodes : nodes,
                materials : materials,
                name : name
            };
        });
}

function loadMtls(mtlPaths, objPath, options) {
    var objDirectory = path.dirname(objPath);
    var materials = [];

    // Remove duplicates
    mtlPaths = mtlPaths.filter(function(value, index, self) {
        return self.indexOf(value) === index;
    });

    return Promise.map(mtlPaths, function(mtlPath) {
        mtlPath = path.resolve(objDirectory, mtlPath);
        var shallowPath = path.resolve(path.join(objDirectory, path.basename(mtlPath)));
        if (options.secure && outsideDirectory(mtlPath, objDirectory)) {
            // Try looking for the .mtl in the same directory as the obj
            options.logger('The material file is outside of the obj directory and the secure flag is true. Attempting to read the material file from within the obj directory instead.');
            return loadMtl(shallowPath, options)
                .then(function(materialsInMtl) {
                    materials = materials.concat(materialsInMtl);
                })
                .catch(function(error) {
                    options.logger(error.message);
                    options.logger('Could not read material file at ' + shallowPath + '. Using default material instead.');
                });
        }

        return loadMtl(mtlPath, options)
            .catch(function(error) {
                // Try looking for the .mtl in the same directory as the obj
                options.logger(error.message);
                options.logger('Could not read material file at ' + mtlPath + '. Attempting to read the material file from within the obj directory instead.');
                return loadMtl(shallowPath, options);
            })
            .then(function(materialsInMtl) {
                materials = materials.concat(materialsInMtl);
            })
            .catch(function(error) {
                options.logger(error.message);
                options.logger('Could not read material file at ' + shallowPath + '. Using default material instead.');
            });
    }, {concurrency : 10})
        .then(function() {
            return materials;
        });
}

function assignDefaultMaterial(nodes, materials) {
    if (materials.length === 0) {
        return;
    }
    var defaultMaterial = materials[0].name;
    var nodesLength = nodes.length;
    for (var i = 0; i < nodesLength; ++i) {
        var meshes = nodes[i].meshes;
        var meshesLength = meshes.length;
        for (var j = 0; j < meshesLength; ++j) {
            var primitives = meshes[j].primitives;
            var primitivesLength = primitives.length;
            for (var k = 0; k < primitivesLength; ++k) {
                var primitive = primitives[k];
                primitive.material = defaultValue(primitive.material, defaultMaterial);
            }
        }
    }
}

function removeEmptyMeshes(meshes) {
    return meshes.filter(function(mesh) {
        // Remove empty primitives
        mesh.primitives = mesh.primitives.filter(function(primitive) {
            return primitive.indices.length > 0;
        });
        // Valid meshes must have at least one primitive and contain positions
        return (mesh.primitives.length > 0) && (mesh.positions.length > 0);
    });
}

function meshesHaveNames(meshes) {
    var meshesLength = meshes.length;
    for (var i = 0; i < meshesLength; ++i) {
        if (defined(meshes[i].name)) {
            return true;
        }
    }
    return false;
}

function removeEmptyNodes(nodes) {
    var final = [];
    var nodesLength = nodes.length;
    for (var i = 0; i < nodesLength; ++i) {
        var node = nodes[i];
        var meshes = removeEmptyMeshes(node.meshes);
        if (meshes.length === 0) {
            continue;
        }
        node.meshes = meshes;
        if (!defined(node.name) && meshesHaveNames(meshes)) {
            // If the obj has groups (g) but not object groups (o) then convert meshes to nodes
            var meshesLength = meshes.length;
            for (var j = 0; j < meshesLength; ++j) {
                var mesh = meshes[j];
                var convertedNode = new Node();
                convertedNode.name = mesh.name;
                convertedNode.meshes = [mesh];
                final.push(convertedNode);
            }
        } else {
            final.push(node);
        }
    }
    return final;
}

function setDefaultNames(items, defaultName, usedNames) {
    var itemsLength = items.length;
    for (var i = 0; i < itemsLength; ++i) {
        var item = items[i];
        var name = defaultValue(item.name, defaultName);
        var occurrences = usedNames[name];
        if (defined(occurrences)) {
            usedNames[name]++;
            name = name + '_' + occurrences;
        } else {
            usedNames[name] = 1;
        }
        item.name = name;
    }
}

function setDefaults(nodes) {
    var usedNames = {};
    setDefaultNames(nodes, 'Node', usedNames);
    var nodesLength = nodes.length;
    for (var i = 0; i < nodesLength; ++i) {
        var node = nodes[i];
        setDefaultNames(node.meshes, node.name + '-Mesh', usedNames);
    }
}

function cleanNodes(nodes) {
    nodes = removeEmptyNodes(nodes);
    setDefaults(nodes);
    return nodes;
}