'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 Cartesian3 = Cesium.Cartesian3;
var ComponentDatatype = Cesium.ComponentDatatype;
var CoplanarPolygonGeometryLibrary = Cesium.CoplanarPolygonGeometryLibrary;
var defaultValue = Cesium.defaultValue;
var defined = Cesium.defined;
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"

/**
 * 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 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 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];
                clearVertexCache();
                vertexCount = primitive.positions.length / 3;
                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);
            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;
        var firstFace = primitive.indices.length === 0;
        var faceHasUvs = uvs[0].length > 0;
        var faceHasNormals = normals[0].length > 0;
        var primitiveHasUvs = primitive.uvs.length > 0;
        var primitiveHasNormals = primitive.normals.length > 0;

        if (!firstFace && (faceHasUvs !== primitiveHasUvs || faceHasNormals !== primitiveHasNormals)) {
            // Discard faces that don't use the same attributes
            return;
        }

        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) {
            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, 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) {
        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) {
            if (materials.length > 0 && !usesMaterials) {
                assignDefaultMaterial(nodes, materials, usesMaterials);
            }
            return {
                nodes : nodes,
                materials : materials,
                name : name
            };
        });
}

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

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 = normalizeMtlPath(mtlPath, objDirectory);
        var shallowPath = 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) {
    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 && 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;
}