const path = require(`path`)
const _ = require('lodash')
const { createFilePath } = require(`gatsby-source-filesystem`)

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

  const blogPost = path.resolve(`./src/templates/blog-post.js`)
  const tagTemplate = path.resolve(`./src/templates/tags.js`)

  return graphql(
    `
      {
        allMarkdownRemark(
          sort: { fields: [frontmatter___date], order: DESC }
          limit: 1000
        ) {
          edges {
            node {
              fields {
                slug
              }
              frontmatter {
                title
                tags
                img {
                  childImageSharp {
                    gatsbyImageData(placeholder: BLURRED, layout: FULL_WIDTH)
                  }
                }
              }
            }
          }
        }
      }
    `
  ).then((result) => {
    if (result.errors) {
      throw result.errors
    }

    // Create blog posts pages.
    const posts = result.data.allMarkdownRemark.edges

    posts.forEach((post, index) => {
      const previous = index === posts.length - 1 ? null : posts[index + 1].node
      const next = index === 0 ? null : posts[index - 1].node

      createPage({
        path: post.node.fields.slug,
        component: blogPost,
        context: {
          slug: post.node.fields.slug,
          previous,
          next,
        },
      })
    })

    // Create blog post list pages
    const postsPerPage = 10
    const numPages = Math.ceil(posts.length / postsPerPage)

    Array.from({ length: numPages }).forEach((_, i) => {
      createPage({
        path: i === 0 ? `/` : `/${i + 1}`,
        component: path.resolve('./src/templates/blog-list.js'),
        context: {
          limit: postsPerPage,
          skip: i * postsPerPage,
          numPages,
          currentPage: i + 1,
        },
      })
    })

    // create Tags pages
    // pulled directly from https://www.gatsbyjs.org/docs/adding-tags-and-categories-to-blog-posts/#add-tags-to-your-markdown-files
    let tags = []
    // Iterate through each post, putting all found tags into `tags`
    _.each(posts, (edge) => {
      if (_.get(edge, 'node.frontmatter.tags')) {
        tags = tags.concat(edge.node.frontmatter.tags)
      }
    })
    // Eliminate duplicate tags
    tags = _.uniq(tags)
    // Make tag pages
    tags.forEach((tag) => {
      createPage({
        path: `/tags/${_.kebabCase(tag)}/`,
        component: tagTemplate,
        context: {
          tag,
        },
      })
    })
  })
}

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions

  if (node.internal.type === `MarkdownRemark`) {
    const value = createFilePath({ node, getNode })
    createNodeField({
      name: `slug`,
      node,
      value,
    })
  }
}