const readWasm = require('./read-wasm')

/**
 * Provide the JIT with a nice shape / hidden class.
 */
function Mapping() {
  this.generatedLine = 0
  this.generatedColumn = 0
  this.lastGeneratedColumn = null
  this.source = null
  this.originalLine = null
  this.originalColumn = null
  this.name = null
}

let cachedWasm = null

module.exports = function wasm() {
  if (cachedWasm) {
    return cachedWasm
  }

  const callbackStack = []

  cachedWasm = readWasm()
    .then((buffer) => {
      return WebAssembly.instantiate(buffer, {
        env: {
          mapping_callback(
            generatedLine,
            generatedColumn,

            hasLastGeneratedColumn,
            lastGeneratedColumn,

            hasOriginal,
            source,
            originalLine,
            originalColumn,

            hasName,
            name
          ) {
            const mapping = new Mapping()
            // JS uses 1-based line numbers, wasm uses 0-based.
            mapping.generatedLine = generatedLine + 1
            mapping.generatedColumn = generatedColumn

            if (hasLastGeneratedColumn) {
              // JS uses inclusive last generated column, wasm uses exclusive.
              mapping.lastGeneratedColumn = lastGeneratedColumn - 1
            }

            if (hasOriginal) {
              mapping.source = source
              // JS uses 1-based line numbers, wasm uses 0-based.
              mapping.originalLine = originalLine + 1
              mapping.originalColumn = originalColumn

              if (hasName) {
                mapping.name = name
              }
            }

            callbackStack[callbackStack.length - 1](mapping)
          },

          start_all_generated_locations_for() {
            console.time('all_generated_locations_for')
          },
          end_all_generated_locations_for() {
            console.timeEnd('all_generated_locations_for')
          },

          start_compute_column_spans() {
            console.time('compute_column_spans')
          },
          end_compute_column_spans() {
            console.timeEnd('compute_column_spans')
          },

          start_generated_location_for() {
            console.time('generated_location_for')
          },
          end_generated_location_for() {
            console.timeEnd('generated_location_for')
          },

          start_original_location_for() {
            console.time('original_location_for')
          },
          end_original_location_for() {
            console.timeEnd('original_location_for')
          },

          start_parse_mappings() {
            console.time('parse_mappings')
          },
          end_parse_mappings() {
            console.timeEnd('parse_mappings')
          },

          start_sort_by_generated_location() {
            console.time('sort_by_generated_location')
          },
          end_sort_by_generated_location() {
            console.timeEnd('sort_by_generated_location')
          },

          start_sort_by_original_location() {
            console.time('sort_by_original_location')
          },
          end_sort_by_original_location() {
            console.timeEnd('sort_by_original_location')
          },
        },
      })
    })
    .then((Wasm) => {
      return {
        exports: Wasm.instance.exports,
        withMappingCallback: (mappingCallback, f) => {
          callbackStack.push(mappingCallback)
          try {
            f()
          } finally {
            callbackStack.pop()
          }
        },
      }
    })
    .then(null, (e) => {
      cachedWasm = null
      throw e
    })

  return cachedWasm
}
