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

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

var Axis = Cesium.Axis;
var Cartesian3 = Cesium.Cartesian3;
var ComponentDatatype = Cesium.ComponentDatatype;
var CoplanarPolygonGeometryLibrary = Cesium.CoplanarPolygonGeometryLibrary;
var defaultValue = Cesium.defaultValue;
var defined = Cesium.defined;
var Matrix4 = Cesium.Matrix4;
var PolygonPipeline = Cesium.PolygonPipeline;
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 = [];
}

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

// 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"

var scratchCartesian = new Cartesian3();

/**
 * Parse an obj file.
 *
 * @param {String} objPath Path to the obj file.
 * @param {Object} options An object with the following properties:
 * @param {Boolean} options.checkTransparency Do a more exhaustive check for texture transparency by looking at the alpha channel of each pixel.
 * @param {Boolean} options.secure Prevent the converter from reading image or mtl files outside of the input obj directory.
 * @param {String} options.inputUpAxis Up axis of the obj.
 * @param {String} options.outputUpAxis Up axis of the converted glTF.
 * @param {Boolean} options.logger A callback function for handling logged messages. Defaults to console.log.
 * @returns {Promise} A promise resolving to the obj data.
 * @exception {RuntimeError} The file does not have any geometry information in it.
 *
 * @private
 */
function loadObj(objPath, options) {
    var axisTransform = getAxisTransform(options.inputUpAxis, options.outputUpAxis);

    // 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 primitive.
    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 = [];

    function clearVertexCache() {
        vertexCache = {};
        vertexCacheCount = 0;
    }

    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();
    }

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

        // Clear the vertex cache for each new primitive
        clearVertexCache();
        vertexCount = 0;
    }

    function reusePrimitive(callback) {
        var primitives = mesh.primitives;
        var primitivesLength = primitives.length;
        for (var i = 0; i < primitivesLength; ++i) {
            if (primitives[i].material === activeMaterial) {
                if (!defined(callback) || callback(primitives[i])) {
                    primitive = primitives[i];
                    clearVertexCache();
                    vertexCount = primitive.positions.length / 3;
                    return;
                }
            }
        }
        addPrimitive();
    }

    function useMaterial(name) {
        activeMaterial = getName(name);
        reusePrimitive();
    }

    function faceAndPrimitiveMatch(uvs, normals, primitive) {
        var faceHasUvs = uvs[0].length > 0;
        var faceHasNormals = normals[0].length > 0;
        var primitiveHasUvs = primitive.uvs.length > 0;
        var primitiveHasNormals = primitive.normals.length > 0;
        return primitiveHasUvs === faceHasUvs && primitiveHasNormals === faceHasNormals;
    }

    function checkPrimitive(uvs, normals) {
        var firstFace = primitive.indices.length === 0;
        if (!firstFace && !faceAndPrimitiveMatch(uvs, normals, primitive)) {
            reusePrimitive(function(primitive) {
                return faceAndPrimitiveMatch(uvs, normals, primitive);
            });
        }
    }

    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);
            primitive.positions.push(px);
            primitive.positions.push(py);
            primitive.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);
            primitive.normals.push(nx);
            primitive.normals.push(ny);
            primitive.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);
            primitive.uvs.push(ux);
            primitive.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) {
                clearVertexCache();
            }
        }
        return index;
    }

    function getPosition(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 getNormal(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);
    }

    var scratch1 = new Cartesian3();
    var scratch2 = new Cartesian3();
    var scratch3 = new Cartesian3();
    var scratch4 = new Cartesian3();
    var scratch5 = new Cartesian3();
    var scratchCenter = new Cartesian3();
    var scratchAxis1 = new Cartesian3();
    var scratchAxis2 = new Cartesian3();
    var scratchNormal = new Cartesian3();
    var scratchPositions = [new Cartesian3(), new Cartesian3(), new Cartesian3(), new Cartesian3()];
    var scratchVertexIndices = [];
    var scratchPoints = [];

    function checkWindingCorrect(positionIndex1, positionIndex2, positionIndex3, normalIndex) {
        if (normalIndex.length === 0) {
            // If no face normal, we have to assume the winding is correct.
            return true;
        }
        var normal = getNormal(normalIndex, scratchNormal);
        var A = getPosition(positionIndex1, scratch1);
        var B = getPosition(positionIndex2, scratch2);
        var C = getPosition(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);
        }
    }

    function addFace(vertices, positions, uvs, normals) {
        var i;
        var isWindingCorrect;
        checkPrimitive(uvs, normals);

        if (vertices.length === 3) {
            isWindingCorrect = checkWindingCorrect(positions[0], positions[1], positions[2], normals[0]);
            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 points = scratchPoints;
            var vertexIndices = scratchVertexIndices;

            points.length = 0;
            vertexIndices.length = 0;

            for (i = 0; i < vertices.length; ++i) {
                var index = addVertex(vertices[i], positions[i], uvs[i], normals[i]);
                vertexIndices.push(index);
                if (i === scratchPositions.length) {
                    scratchPositions.push(new Cartesian3());
                }
                points.push(getPosition(positions[i], scratchPositions[i]));
            }

            var validGeometry = CoplanarPolygonGeometryLibrary.computeProjectTo2DArguments(points, scratchCenter, scratchAxis1, scratchAxis2);
            if (!validGeometry) {
                return;
            }
            var projectPoints = CoplanarPolygonGeometryLibrary.createProjectPointsTo2DFunction(scratchCenter, scratchAxis1, scratchAxis2);
            var points2D = projectPoints(points);
            var indices = PolygonPipeline.triangulate(points2D);
            isWindingCorrect = PolygonPipeline.computeWindingOrder2D(points2D) !== WindingOrder.CLOCKWISE;

            for (i = 0; i < indices.length - 2; i += 3) {
                addTriangle(vertexIndices[indices[i]], vertexIndices[indices[i+1]], vertexIndices[indices[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) {
            var position = scratchCartesian;
            position.x = parseFloat(result[1]);
            position.y = parseFloat(result[2]);
            position.z = parseFloat(result[3]);
            if (defined(axisTransform)) {
                Matrix4.multiplyByPoint(axisTransform, position, position);
            }
            positions.push(position.x);
            positions.push(position.y);
            positions.push(position.z);
        } 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);
            }
            if (defined(axisTransform)) {
                Matrix4.multiplyByPointAsVector(axisTransform, 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() {
            // Unload resources
            positions = undefined;
            normals = undefined;
            uvs = undefined;

            // Load materials and images
            return finishLoading(nodes, mtlPaths, objPath, defined(activeMaterial), 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, usesMaterials, options) {
    nodes = cleanNodes(nodes);
    if (nodes.length === 0) {
        return Promise.reject(new RuntimeError(objPath + ' does not have any geometry data'));
    }
    return loadMaterials(mtlPaths, objPath, options)
        .then(function(materials) {
            if (Object.keys(materials).length > 0 && !usesMaterials) {
                assignDefaultMaterial(nodes, materials, usesMaterials);
            }
            var imagePaths = getImagePaths(materials);
            return loadImages(imagePaths, objPath, options)
                .then(function(images) {
                    return {
                        nodes : nodes,
                        materials : materials,
                        images : images
                    };
                });
        });
}

function normalizeMtlPath(mtlPath, objDirectory) {
    mtlPath = mtlPath.replace(/\\/g, '/');
    return path.normalize(path.join(objDirectory, mtlPath));
}

function outsideDirectory(filePath, objPath) {
    return (path.relative(path.dirname(objPath), filePath).indexOf('..') === 0);
}

function loadMaterials(mtlPaths, objPath, options) {
    var secure = options.secure;
    var logger = options.logger;
    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 = normalizeMtlPath(mtlPath, objDirectory);
        if (secure && outsideDirectory(mtlPath, objPath)) {
            logger('Could not read mtl file at ' + mtlPath + ' because it is outside of the obj directory and the secure flag is true. Using default material instead.');
            return;
        }
        return loadMtl(mtlPath)
            .then(function(materialsInMtl) {
                materials = Object.assign(materials, materialsInMtl);
            })
            .catch(function() {
                logger('Could not read mtl file at ' + mtlPath + '. Using default material instead.');
            });
    }, {concurrency : 10})
        .thenReturn(materials);
}

function loadImages(imagePaths, objPath, options) {
    var secure = options.secure;
    var logger = options.logger;
    var images = {};
    return Promise.map(imagePaths, function(imagePath) {
        if (secure && outsideDirectory(imagePath, objPath)) {
            logger('Could not read image file at ' + imagePath + ' because it is outside of the obj directory and the secure flag is true. Material will ignore this image.');
            return;
        }
        return loadImage(imagePath, options)
            .then(function(image) {
                images[imagePath] = image;
            })
            .catch(function() {
                logger('Could not read image file at ' + imagePath + '. Material will ignore this image.');
            });
    }, {concurrency : 10})
        .thenReturn(images);
}

function getImagePaths(materials) {
    var imagePaths = {};
    for (var name in materials) {
        if (materials.hasOwnProperty(name)) {
            var material = materials[name];
            if (defined(material.ambientTexture)) {
                imagePaths[material.ambientTexture] = true;
            }
            if (defined(material.diffuseTexture)) {
                imagePaths[material.diffuseTexture] = true;
            }
            if (defined(material.emissionTexture)) {
                imagePaths[material.emissionTexture] = true;
            }
            if (defined(material.specularTexture)) {
                imagePaths[material.specularTexture] = true;
            }
        }
    }
    return Object.keys(imagePaths);
}

function assignDefaultMaterial(nodes, materials) {
    var defaultMaterial = Object.keys(materials)[0];
    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 && primitive.positions.length > 0;
        });
        // Valid meshes must have at least one primitive
        return (mesh.primitives.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;
}

function getAxisTransform(inputUpAxis, outputUpAxis) {
    if (inputUpAxis === 'X' && outputUpAxis === 'Y') {
        return Axis.X_UP_TO_Y_UP;
    } else if (inputUpAxis === 'X' && outputUpAxis === 'Z') {
        return Axis.X_UP_TO_Z_UP;
    } else if (inputUpAxis === 'Y' && outputUpAxis === 'X') {
        return Axis.Y_UP_TO_X_UP;
    } else if (inputUpAxis === 'Y' && outputUpAxis === 'Z') {
        return Axis.Y_UP_TO_Z_UP;
    } else if (inputUpAxis === 'Z' && outputUpAxis === 'X') {
        return Axis.Z_UP_TO_X_UP;
    } else if (inputUpAxis === 'Z' && outputUpAxis === 'Y') {
        return Axis.Z_UP_TO_Y_UP;
    }
}