Try and suggest fixes for typos

gleam.toml

@@ -29,6 +29,8 @@ gleamsver = ">= 1.0.1 and < 2.0.0"
 porter_stemmer = ">= 1.0.0 and < 2.0.0"
 gleam_time = ">= 1.2.0 and < 2.0.0"
 gleam_httpc = ">= 5.0.0 and < 6.0.0"
+edit_distance = ">= 3.0.0 and < 4.0.0"
+cell = ">= 1.0.0 and < 2.0.0"
 
 [dev-dependencies]
 gleeunit = "~> 1.0"

manifest.toml

@@ -3,7 +3,9 @@
 
 packages = [
   { name = "argv", version = "1.0.2", build_tools = ["gleam"], requirements = [], otp_app = "argv", source = "hex", outer_checksum = "BA1FF0929525DEBA1CE67256E5ADF77A7CDDFE729E3E3F57A5BDCAA031DED09D" },
+  { name = "cell", version = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "cell", source = "hex", outer_checksum = "4200D6FD95E7E720F9376FD4670E7ACC2E6847CF129514D91EB1583218E1C351" },
   { name = "directories", version = "1.2.0", build_tools = ["gleam"], requirements = ["envoy", "gleam_stdlib", "platform", "simplifile"], otp_app = "directories", source = "hex", outer_checksum = "D13090CFCDF6759B87217E8DDD73A75903A700148A82C1D33799F333E249BF9E" },
+  { name = "edit_distance", version = "3.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "edit_distance", source = "hex", outer_checksum = "7DC465C34695F9E57D79FC65670C53C992CE342BF29E0AA41FF44F61AF62FC56" },
   { name = "envoy", version = "1.0.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "envoy", source = "hex", outer_checksum = "95FD059345AA982E89A0B6E2A3BF1CF43E17A7048DCD85B5B65D3B9E4E39D359" },
   { name = "exception", version = "2.1.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "exception", source = "hex", outer_checksum = "329D269D5C2A314F7364BD2711372B6F2C58FA6F39981572E5CA68624D291F8C" },
   { name = "filepath", version = "1.1.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "B06A9AF0BF10E51401D64B98E4B627F1D2E48C154967DA7AF4D0914780A6D40A" },
@@ -38,6 +40,8 @@ packages = [
 
 [requirements]
 argv = { version = "~> 1.0" }
+cell = { version = ">= 1.0.0 and < 2.0.0" }
+edit_distance = { version = ">= 3.0.0 and < 4.0.0" }
 envoy = { version = ">= 1.0.2 and < 2.0.0" }
 gleam_erlang = { version = ">= 1.3.0 and < 2.0.0" }
 gleam_hexpm = { version = ">= 3.0.0 and < 4.0.0" }

src/packages/error.gleam

@@ -8,5 +8,6 @@ pub type Error {
   HttpClientError(httpc.HttpError)
   JsonDecodeError(json.DecodeError)
   StorageError(storail.StorailError)
-  EtsTableError
+  TextIndexEtsTableError
+  KnownWordsEtsTableError
 }

src/packages/router.gleam

@@ -140,13 +140,23 @@ fn internet_points(ctx: Context) -> Response {
 
 fn search(request: Request, context: Context) -> Response {
   let search_term = get_search_parameter(request)
-  let assert Ok(packages) = case search_term {
-    "" -> storage.packages_most_recent_first(context.db)
+  let assert Ok(search_outcome) = case search_term {
+    "" ->
+      storage.packages_most_recent_first(context.db)
+      |> result.map(storage.Packages)
+
     _ -> storage.search_packages(context.db, context.search_index, search_term)
   }
 
-  page.packages_list(packages, search_term)
-  |> wisp.html_response(200)
+  case search_outcome {
+    storage.Packages(packages:) ->
+      page.packages_list(packages, search_term)
+      |> wisp.html_response(200)
+
+    storage.DidYouMean(suggestion:) ->
+      page.did_you_mean(suggestion, search_term)
+      |> wisp.html_response(200)
+  }
 }
 
 fn get_search_parameter(request: Request) -> String {

src/packages/storage.gleam

@@ -370,39 +370,44 @@ pub fn list_packages(database: Database) -> Result(List(String), Error) {
   }
 }
 
+pub type SearchOutcome {
+  Packages(packages: List(Package))
+  DidYouMean(suggestion: String)
+}
+
 pub fn search_packages(
   db: Database,
   search: text_search.TextSearchIndex,
   search_term: String,
-) -> Result(List(Package), Error) {
-  let bool = fn(b) {
-    case b {
-      True -> 1
-      False -> 0
-    }
-  }
+) -> Result(SearchOutcome, Error) {
   use found <- result.try(text_search.lookup(search, search_term))
+
+  case found {
+    [_, ..] ->
+      rank_found_results(found, db, search_term)
+      |> result.map(Packages)
+
+    // If no results are found we try and suggest a fix for the search term.
+    [] ->
+      case text_search.did_you_mean(search, search_term) {
+        Ok(suggestion) -> Ok(DidYouMean(suggestion:))
+        Error(_) -> Ok(Packages(packages: []))
+      }
+  }
+}
+
+/// Given a list of `text_search` results, this returns a list of the matching
+/// packages, ranked from most relevant to least relevant.
+///
+fn rank_found_results(
+  found: List(text_search.Found),
+  db: Database,
+  search_term: String,
+) -> Result(List(Package), Error) {
   use packages <- result.map(
     list.try_map(found, fn(found) {
       use package <- result.map(get_package(db, found.name))
-
-      let exact_package_name_match = bool(search_term == package.name)
-      let is_not_v0 = bool(!string.starts_with(package.latest_version, "0."))
-      let is_core_package = bool(override.is_core_package(package.name))
-      let updated_at =
-        float.round(timestamp.to_unix_seconds(package.updated_in_hex_at))
-
-      // This is the value we use to determine what order packages should be
-      // shown by. Later list values only take effect if the earlier ones are
-      // equal.
-      let ordering_key = [
-        exact_package_name_match,
-        is_not_v0,
-        found.match_count,
-        is_core_package,
-        package.downloads_recent,
-        updated_at,
-      ]
+      let ordering_key = package_ordering_key(search_term, package, found)
       #(ordering_key, package)
     }),
   )
@@ -412,6 +417,38 @@ pub fn search_packages(
   |> list.map(fn(pair) { pair.1 })
 }
 
+/// This is the value we use to determine what order packages should be shown
+/// by.
+///
+fn package_ordering_key(
+  search_term: String,
+  package: Package,
+  found: text_search.Found,
+) -> List(Int) {
+  let bool = fn(bool) {
+    case bool {
+      True -> 1
+      False -> 0
+    }
+  }
+
+  let exact_package_name_match = bool(search_term == package.name)
+  let is_not_v0 = bool(!string.starts_with(package.latest_version, "0."))
+  let is_core_package = bool(override.is_core_package(package.name))
+  let updated_at =
+    float.round(timestamp.to_unix_seconds(package.updated_in_hex_at))
+
+  // Later list values only take effect if the earlier ones are equal.
+  [
+    exact_package_name_match,
+    is_not_v0,
+    found.match_count,
+    is_core_package,
+    package.downloads_recent,
+    updated_at,
+  ]
+}
+
 fn list_compare(
   a: List(t),
   b: List(t),