var collection_json = require('collection_json')
  , pg = require('pg').native
  , _ = require('underscore');

function mapRow(row) {
  var data = _.map(row, function(value, key) {
      return {name: key, value: value};
  });
  return { data: data };
}

function mapDepartments(res, departments) {
  return _.map(departments, function(row) {
    var item = mapRow(row);
    item.href = res.urlgenerator.department(row.dept_no);
    return item;
  });
}

function mapEmployees(res, employees) {
  return _.map(employees, function(row) {
    var item = mapRow(row);
    item.href = res.urlgenerator.employee(row.emp_no);
    return item;
  });
}

function pager(req) {
  var pageSize = 10;
  var offset = parseInt(req.query.offset) || 0;
  var limit = parseInt(req.query.limit) || pageSize;
  var prevOffset = offset - pageSize;
  var nextOffset = offset + pageSize;
  return {
    offset: offset,
    limit: limit,
    prevOffset: prevOffset >= 0 ? prevOffset : 0,
    nextOffset: function(length) {
      return length > 0 ? nextOffset : undefined;
    }
  };
}

exports.index = function(req, res) {
  if(req.accepts('html')) {
    res.render('index', {
      title: 'Employee DB',
      urlgenerator: res.urlgenerator
    });
  }
  else {
    var c = {collection: {
      links: [ {
        rel: 'departments',
        prompt: 'Department List',
        href: res.urlgenerator.departments()
      }, {
        rel: 'employees',
        prompt: 'Employee List',
        href: res.urlgenerator.employees()
      } ]
    }};
    res.contentType('application/vnd.collection+json');
    res.send(JSON.stringify(collection_json.fromObject(c)), 200);
  }
};

exports.departments = function(req, res) {
  pg.connect(process.env.DATABASE_URL, function(err, client) {
    if(err) throw err;
    var p = pager(req);
    var departments = [];
    client.query('SELECT dept_no, dept_name FROM departments OFFSET $1 LIMIT $2', [ p.offset, p.limit ] ).
    on('row', function(row) {
      departments.push(row);
    }).
    on('end', function() {
      if(req.accepts('html')) {
        res.render('departments', {
          title: 'Department List',
          urlgenerator: res.urlgenerator, pager: p,
          departments: departments
        });
      }
      else {
        var c = {collection: {
          href: res.urlgenerator.departments(),
          items: mapDepartments(res, departments)
        }};
        res.contentType('application/vnd.collection+json');
        res.send(JSON.stringify(collection_json.fromObject(c)), 200);
      }
    });
  });
};

exports.department = function(req, res) {
  var dept_no = req.params.dept_no;
  if(req.accepts('html')) {
    res.render('department', {
      title: 'Department ' + dept_no,
      urlgenerator: res.urlgenerator,
      dept_no: dept_no
    });
  }
  else {
    var c = {collection: {
      href: res.urlgenerator.department(dept_no),
      links: [ {
        rel: 'employees',
        prompt: 'Employees in department ' + dept_no,
        href: res.urlgenerator.employees_in_department(dept_no)
      },{
        rel: 'departments',
        prompt: 'All departments',
        href: res.urlgenerator.departments()
      } ]
    }};
    res.contentType('application/vnd.collection+json');
    res.send(collection_json.fromObject(c));
  }
}

exports.employees_in_department = function(req, res) {
  pg.connect(process.env.DATABASE_URL, function(err, client) {
    if(err) throw err;
    var dept_no = req.params.dept_no;
    var p = pager(req);
    var employees = [];
    // TODO: Add dept_name to view
    // TODO: Add manager as a link
    client.query('SELECT employees.* FROM employees, dept_emp WHERE employees.emp_no=dept_emp.emp_no AND dept_emp.dept_no=$1 AND dept_emp.to_date > now() AND now() > dept_emp.from_date OFFSET $2 LIMIT $3', [ dept_no, p.offset, p.limit ]).
    on('row', function(row) {
      employees.push(row);
    }).
    on('end', function() {
      if(req.accepts('html')) {
        res.render('employees_in_department', {
          title: 'Department: #' + dept_no,
          urlgenerator: res.urlgenerator, pager: p,
          dept_no: dept_no,
          employees: employees
        });
      }
      else {
        var c = {collection: {
          href: res.urlgenerator.employees_in_department(dept_no),
          links: [ {
            rel: 'department',
            prompt: 'Department: #' + dept_no,
            href: res.urlgenerator.department(dept_no)
          } ],
          items: mapEmployees(res, employees)
        }};
        res.contentType('application/vnd.collection+json');
        res.send(collection_json.fromObject(c));
      }
    });
  });
};

exports.employees = function(req, res) {
  pg.connect(process.env.DATABASE_URL, function(err, client) {
    if(err) throw err;
    var p = pager(req);
    var emp_no = req.params.emp_no;
    var employees = [];
    client.query('SELECT * FROM employees ORDER BY emp_no OFFSET $1 LIMIT $2', [ p.offset, p.limit ]).
    on('row', function(row) {
      employees.push(row);
    }).
    on('end', function() {
      if(req.accepts('html')) {
        res.render('employees', {
          title: 'Employee List',
          urlgenerator: res.urlgenerator, pager: p,
          employees: employees
        });
      }
      else {
        var c = {collection: {
          href: res.urlgenerator.employees(),
          items: mapEmployees(res, employees)
        }};
        res.contentType('application/vnd.collection+json');
        res.send(JSON.stringify(collection_json.fromObject(c)), 200);
      }
    });
  });
};

exports.employee = function(req, res) {
  pg.connect(process.env.DATABASE_URL, function(err, client) {
    if(err) throw err;
    var emp_no = req.params.emp_no;
    var employee;
    client.query('SELECT * FROM employees WHERE employees.emp_no=$1', [ emp_no ]).
    on('row', function(row) {
      employee = row;
    }).
    on('end', function() {
      if(req.accepts('html')) {
        res.render('employee', {
          title: 'Employee: #' + emp_no,
          urlgenerator: res.urlgenerator,
          employee: employee
        });
      }
      else {
        var c = {collection: {
          href: res.urlgenerator.employee(emp_no),
          items: [ mapRow(employee) ],
        }};
        res.contentType('application/vnd.collection+json');
        res.send(JSON.stringify(collection_json.fromObject(c)), 200);
      }
    });
  });
};