const path = require('path')

const NEXT_EXPORT_FUNCTIONS = [
  'getStaticProps',
  'getStaticPaths',
  'getServerSideProps',
]

// 0 is the exact match
const THRESHOLD = 1

// the minimum number of operations required to convert string a to string b.
function minDistance(a, b) {
  const m = a.length
  const n = b.length

  if (m < n) {
    return minDistance(b, a)
  }

  if (n === 0) {
    return m
  }

  let previousRow = Array.from({ length: n + 1 }, (_, i) => i)

  for (let i = 0; i < m; i++) {
    const s1 = a[i]
    let currentRow = [i + 1]
    for (let j = 0; j < n; j++) {
      const s2 = b[j]
      const insertions = previousRow[j + 1] + 1
      const deletions = currentRow[j] + 1
      const substitutions = previousRow[j] + Number(s1 !== s2)
      currentRow.push(Math.min(insertions, deletions, substitutions))
    }
    previousRow = currentRow
  }
  return previousRow[previousRow.length - 1]
}

module.exports = {
  meta: {
    docs: {
      description: 'Prevent common typos',
      category: 'Stylistic Issues',
      recommended: true,
    },
    fixable: null,
  },

  create: function (context) {
    function checkTypos(node, name) {
      if (NEXT_EXPORT_FUNCTIONS.includes(name)) {
        return
      }

      const potentialTypos = NEXT_EXPORT_FUNCTIONS.map((o) => ({
        option: o,
        distance: minDistance(o, name),
      }))
        .filter(({ distance }) => distance <= THRESHOLD && distance > 0)
        .sort((a, b) => a.distance - b.distance)

      if (potentialTypos.length) {
        context.report({
          node,
          message: `${name} may be a typo. Did you mean ${potentialTypos[0].option}?`,
        })
      }
    }
    return {
      ExportNamedDeclaration(node) {
        const page = context.getFilename().split('pages')[1]
        if (!page || path.parse(page).dir.startsWith('/api')) {
          return
        }

        const decl = node.declaration

        if (!decl) {
          return
        }

        switch (decl.type) {
          case 'FunctionDeclaration': {
            checkTypos(node, decl.id.name)
            break
          }
          case 'VariableDeclaration': {
            decl.declarations.forEach((d) => {
              if (d.id.type !== 'Identifier') {
                return
              }
              checkTypos(node, d.id.name)
            })
            break
          }
          default: {
            break
          }
        }
        return
      },
    }
  },
}