const path = require('path')

exports.createPages = async ({ actions, graphql }) => {
    const {createPage} = actions;

    const result = await graphql(`
    {
    courses: allMarkdownRemark(
        filter: {frontmatter: {
            content_type: {eq: "page_education"}, 
            published: {eq: true}}}
            ){ 
                edges{
                    node{
                        html
                        frontmatter{
                            title
                            path
                        }
                    }
                }
            }
            
    news: allMarkdownRemark(
        filter: {frontmatter: {content_type: {eq: "post"}, published: {eq: true}}},
        sort: {fields: [frontmatter___date], order: DESC}
        ) {
            edges{
                node{
                    frontmatter{
                        title
                        slug
                        date(formatString: "DD.MM.YYYY")
                    }
                    html
                }
            }
        }
    }`)
            
    if( result.errors ){ throw result.errors; }
                
    const courseTemplate = path.resolve(`./src/components/templates/courseTemplate.js`);
    const courses = result.data.courses.edges;

    courses.forEach(({node}) => {
        createPage({
            path: node.frontmatter.path,
            component: courseTemplate,
        })
    });

    ///////////////////////////////////////////////////////////////////

    const newsTemplate = path.resolve(`./src/components/templates/news.js`);
    const posts = result.data.news.edges;
  
    const postsPerPage = 5;
    const numberOfNewsItems = posts.length;
    const numberOfNewsPages = Math.ceil(numberOfNewsItems / postsPerPage);
  
  
    for (let pageIndex = 0; pageIndex < numberOfNewsPages; pageIndex++) {
      const pageNumber = pageIndex + 1;
      const path = pageIndex === 0 ? '/news' : `/news/${pageNumber}`;
      const skip = pageIndex * postsPerPage;
  
      function getPreviousPageLink() {
        if (!pageIndex) return null
        if (pageIndex === 1) return '/news'
        return `/news/${pageIndex}`
      }
  
      function getNextPageLink() {
        if (pageNumber < numberOfNewsPages) return `news/${pageNumber + 1}`
        return null
      }
  
      createPage({
        path,
        component: newsTemplate,
        context: {
          limit: postsPerPage,
          skip,
          next: getNextPageLink(),
          prev: getPreviousPageLink(),
        },
      })
    }
}