feat: add tags (hashtag) support

Sources/RemindCore/Models.swift

@@ -75,6 +75,39 @@ public struct ReminderItem: Identifiable, Codable, Sendable, Equatable {
     self.listID = listID
     self.listName = listName
   }
+
+  public var tags: [String] {
+    Self.extractTrailingTags(from: title).tags
+  }
+
+  public var titleWithoutTags: String {
+    Self.extractTrailingTags(from: title).title
+  }
+
+  private static let trailingTagPattern = try! NSRegularExpression(
+    pattern: "(?:^|\\s)#([A-Za-z0-9][A-Za-z0-9_-]*)$"
+  )
+
+  private static func extractTrailingTags(from rawTitle: String) -> (title: String, tags: [String]) {
+    var title = rawTitle.trimmingCharacters(in: .whitespacesAndNewlines)
+    var extracted: [String] = []
+
+    while !title.isEmpty {
+      let range = NSRange(title.startIndex..<title.endIndex, in: title)
+      guard let match = trailingTagPattern.firstMatch(in: title, options: [], range: range),
+        let fullRange = Range(match.range(at: 0), in: title),
+        let tagRange = Range(match.range(at: 1), in: title)
+      else {
+        break
+      }
+
+      extracted.append(String(title[tagRange]))
+      title.removeSubrange(fullRange)
+      title = title.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
+    return (title: title, tags: extracted.reversed())
+  }
 }
 
 public struct ReminderDraft: Sendable {

Sources/remindctl/CommandHelpers.swift

@@ -23,4 +23,76 @@ enum CommandHelpers {
     }
     return date
   }
+
+  static func parseTags(_ rawValues: [String]) throws -> [String] {
+    var tags: [String] = []
+    var seen: Set<String> = []
+
+    for raw in rawValues {
+      for candidate in raw.split(separator: ",", omittingEmptySubsequences: false) {
+        var tag = String(candidate).trimmingCharacters(in: .whitespacesAndNewlines)
+        if tag.hasPrefix("#") {
+          tag.removeFirst()
+        }
+        guard !tag.isEmpty else {
+          throw RemindCoreError.operationFailed("Tag cannot be empty")
+        }
+        guard tag.range(of: #"^[A-Za-z0-9][A-Za-z0-9_-]*$"#, options: .regularExpression) != nil else {
+          throw RemindCoreError.operationFailed("Invalid tag: \"\(tag)\"")
+        }
+        let key = tag.lowercased()
+        if seen.insert(key).inserted {
+          tags.append(tag)
+        }
+      }
+    }
+
+    return tags
+  }
+
+  static func parseTitleTags(_ rawTitle: String) -> (baseTitle: String, tags: [String]) {
+    let pattern = #"(?:^|\s)#([A-Za-z0-9][A-Za-z0-9_-]*)$"#
+    var title = rawTitle.trimmingCharacters(in: .whitespacesAndNewlines)
+    var extracted: [String] = []
+
+    while !title.isEmpty,
+      let range = title.range(of: pattern, options: .regularExpression)
+    {
+      let match = String(title[range])
+      let tag = match
+        .trimmingCharacters(in: .whitespacesAndNewlines)
+        .dropFirst()
+      extracted.append(String(tag))
+      title.removeSubrange(range)
+      title = title.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
+    return (baseTitle: title, tags: extracted.reversed())
+  }
+
+  static func composeTitle(baseTitle: String, tags: [String]) -> String {
+    let normalized = tags.map { "#\($0)" }.joined(separator: " ")
+    guard !normalized.isEmpty else { return baseTitle }
+    guard !baseTitle.isEmpty else { return normalized }
+    return "\(baseTitle) \(normalized)"
+  }
+
+  static func mergeTags(existing: [String], add: [String], remove: [String], clear: Bool) -> [String] {
+    var current = clear ? [] : existing
+
+    if !remove.isEmpty {
+      let removeSet = Set(remove.map { $0.lowercased() })
+      current.removeAll { removeSet.contains($0.lowercased()) }
+    }
+
+    var seen = Set(current.map { $0.lowercased() })
+    for tag in add {
+      let key = tag.lowercased()
+      if seen.insert(key).inserted {
+        current.append(tag)
+      }
+    }
+
+    return current
+  }
 }

Sources/remindctl/CommandRouter.swift

@@ -12,6 +12,7 @@ struct CommandRouter {
     self.version = CommandRouter.resolveVersion()
     self.specs = [
       ShowCommand.spec,
+      TagsCommand.spec,
       ListCommand.spec,
       AddCommand.spec,
       EditCommand.spec,

Sources/remindctl/Commands/AddCommand.swift

@@ -18,6 +18,12 @@ enum AddCommand {
             .make(label: "list", names: [.short("l"), .long("list")], help: "List name", parsing: .singleValue),
             .make(label: "due", names: [.short("d"), .long("due")], help: "Due date", parsing: .singleValue),
             .make(label: "notes", names: [.short("n"), .long("notes")], help: "Notes", parsing: .singleValue),
+            .make(
+              label: "tag",
+              names: [.long("tag")],
+              help: "Tag name (repeatable or comma-separated)",
+              parsing: .singleValue
+            ),
             .make(
               label: "priority",
               names: [.short("p"), .long("priority")],
@@ -31,6 +37,8 @@ enum AddCommand {
         "remindctl add \"Buy milk\"",
         "remindctl add --title \"Call mom\" --list Personal --due tomorrow",
         "remindctl add \"Review docs\" --priority high",
+        "remindctl add \"Buy milk\" --tag shopping --tag urgent",
+        "remindctl add \"Buy milk\" --tag shopping,urgent",
       ]
     ) { values, runtime in
       let titleOption = values.option("title")
@@ -56,9 +64,14 @@ enum AddCommand {
       let notes = values.option("notes")
       let dueValue = values.option("due")
       let priorityValue = values.option("priority")
+      let tagValues = values.optionValues("tag")
 
       let dueDate = try dueValue.map(CommandHelpers.parseDueDate)
       let priority = try priorityValue.map(CommandHelpers.parsePriority) ?? .none
+      let tags = try CommandHelpers.parseTags(tagValues)
+      let parsedTitle = CommandHelpers.parseTitleTags(title)
+      let mergedTags = CommandHelpers.mergeTags(existing: parsedTitle.tags, add: tags, remove: [], clear: false)
+      let titleWithTags = CommandHelpers.composeTitle(baseTitle: parsedTitle.baseTitle, tags: mergedTags)
 
       let store = RemindersStore()
       try await store.requestAccess()
@@ -73,7 +86,7 @@ enum AddCommand {
         throw RemindCoreError.operationFailed("No default list found. Specify --list.")
       }
 
-      let draft = ReminderDraft(title: title, notes: notes, dueDate: dueDate, priority: priority)
+      let draft = ReminderDraft(title: titleWithTags, notes: notes, dueDate: dueDate, priority: priority)
       let reminder = try await store.createReminder(draft, listName: targetList)
       OutputRenderer.printReminder(reminder, format: runtime.outputFormat)
     }

Sources/remindctl/Commands/EditCommand.swift

@@ -18,6 +18,18 @@ enum EditCommand {
             .make(label: "list", names: [.short("l"), .long("list")], help: "Move to list", parsing: .singleValue),
             .make(label: "due", names: [.short("d"), .long("due")], help: "Set due date", parsing: .singleValue),
             .make(label: "notes", names: [.short("n"), .long("notes")], help: "Set notes", parsing: .singleValue),
+            .make(
+              label: "tag",
+              names: [.long("tag")],
+              help: "Add tag (repeatable or comma-separated)",
+              parsing: .singleValue
+            ),
+            .make(
+              label: "removeTag",
+              names: [.long("remove-tag")],
+              help: "Remove tag (repeatable or comma-separated)",
+              parsing: .singleValue
+            ),
             .make(
               label: "priority",
               names: [.short("p"), .long("priority")],
@@ -27,6 +39,7 @@ enum EditCommand {
           ],
           flags: [
             .make(label: "clearDue", names: [.long("clear-due")], help: "Clear due date"),
+            .make(label: "clearTags", names: [.long("clear-tags")], help: "Remove all tags"),
             .make(label: "complete", names: [.long("complete")], help: "Mark completed"),
             .make(label: "incomplete", names: [.long("incomplete")], help: "Mark incomplete"),
           ]
@@ -37,6 +50,8 @@ enum EditCommand {
         "remindctl edit 4A83 --due tomorrow",
         "remindctl edit 2 --priority high --notes \"Call before noon\"",
         "remindctl edit 3 --clear-due",
+        "remindctl edit 1 --tag urgent --remove-tag someday",
+        "remindctl edit 1 --clear-tags",
       ]
     ) { values, runtime in
       guard let input = values.argument(0) else {
@@ -51,9 +66,25 @@ enum EditCommand {
         throw RemindCoreError.reminderNotFound(input)
       }
 
-      let title = values.option("title")
+      var title = values.option("title")
       let listName = values.option("list")
       let notes = values.option("notes")
+      let addTags = try CommandHelpers.parseTags(values.optionValues("tag"))
+      let removeTags = try CommandHelpers.parseTags(values.optionValues("removeTag"))
+      let clearTags = values.flag("clearTags")
+      let hasTagChange = !addTags.isEmpty || !removeTags.isEmpty || clearTags
+
+      if hasTagChange {
+        let sourceTitle = title ?? reminder.title
+        let parsed = CommandHelpers.parseTitleTags(sourceTitle)
+        let merged = CommandHelpers.mergeTags(
+          existing: parsed.tags,
+          add: addTags,
+          remove: removeTags,
+          clear: clearTags
+        )
+        title = CommandHelpers.composeTitle(baseTitle: parsed.baseTitle, tags: merged)
+      }
 
       var dueUpdate: Date??
       if let dueValue = values.option("due") {
@@ -78,7 +109,9 @@ enum EditCommand {
       }
       let isCompleted: Bool? = completeFlag ? true : (incompleteFlag ? false : nil)
 
-      if title == nil && listName == nil && notes == nil && dueUpdate == nil && priority == nil && isCompleted == nil {
+      if title == nil && listName == nil && notes == nil && dueUpdate == nil && priority == nil
+        && isCompleted == nil && !hasTagChange
+      {
         throw RemindCoreError.operationFailed("No changes specified")
       }
 

Sources/remindctl/Commands/ShowCommand.swift

@@ -23,7 +23,13 @@ enum ShowCommand {
               names: [.short("l"), .long("list")],
               help: "Limit to a specific list",
               parsing: .singleValue
-            )
+            ),
+            .make(
+              label: "tag",
+              names: [.long("tag")],
+              help: "Filter by tag (repeatable or comma-separated)",
+              parsing: .singleValue
+            ),
           ]
         )
       ),
@@ -33,10 +39,12 @@ enum ShowCommand {
         "remindctl show overdue",
         "remindctl show 2026-01-04",
         "remindctl show --list Work",
+        "remindctl show --tag shopping",
       ]
     ) { values, runtime in
       let listName = values.option("list")
       let filterToken = values.argument(0)
+      let tagFilters = try CommandHelpers.parseTags(values.optionValues("tag")).map { $0.lowercased() }
 
       let filter: ReminderFilter
       if let token = filterToken {
@@ -51,7 +59,17 @@ enum ShowCommand {
       let store = RemindersStore()
       try await store.requestAccess()
       let reminders = try await store.reminders(in: listName)
-      let filtered = ReminderFiltering.apply(reminders, filter: filter)
+      let filteredByDate = ReminderFiltering.apply(reminders, filter: filter)
+      let filtered: [ReminderItem]
+      if tagFilters.isEmpty {
+        filtered = filteredByDate
+      } else {
+        let tagFilterSet = Set(tagFilters)
+        filtered = filteredByDate.filter { reminder in
+          let reminderTags = Set(reminder.tags.map { $0.lowercased() })
+          return !tagFilterSet.isDisjoint(with: reminderTags)
+        }
+      }
       OutputRenderer.printReminders(filtered, format: runtime.outputFormat)
     }
   }

Sources/remindctl/Commands/TagsCommand.swift

@@ -0,0 +1,54 @@
+import Commander
+import Foundation
+import RemindCore
+
+enum TagsCommand {
+  static var spec: CommandSpec {
+    CommandSpec(
+      name: "tags",
+      abstract: "List tags or reminders for a tag",
+      discussion: "Without an argument, prints all tags with counts. With a tag, shows reminders that match it.",
+      signature: CommandSignatures.withRuntimeFlags(
+        CommandSignature(
+          arguments: [
+            .make(label: "tag", help: "Tag name", isOptional: true)
+          ]
+        )
+      ),
+      usageExamples: [
+        "remindctl tags",
+        "remindctl tags shopping",
+      ]
+    ) { values, runtime in
+      let requestedTag = values.argument(0)
+
+      let store = RemindersStore()
+      try await store.requestAccess()
+      let reminders = try await store.reminders(in: nil)
+
+      if let requestedTag {
+        let parsed = try CommandHelpers.parseTags([requestedTag])
+        guard let filterTag = parsed.first, parsed.count == 1 else {
+          throw RemindCoreError.operationFailed("Provide a single tag")
+        }
+        let key = filterTag.lowercased()
+        let matching = reminders.filter { reminder in
+          reminder.tags.contains { $0.lowercased() == key }
+        }
+        OutputRenderer.printReminders(matching, format: runtime.outputFormat)
+        return
+      }
+
+      var byKey: [String: TagSummary] = [:]
+      for reminder in reminders {
+        for tag in reminder.tags {
+          let key = tag.lowercased()
+          let existing = byKey[key]
+          byKey[key] = TagSummary(tag: existing?.tag ?? tag, count: (existing?.count ?? 0) + 1)
+        }
+      }
+
+      OutputRenderer.printTagSummaries(Array(byKey.values), format: runtime.outputFormat)
+    }
+  }
+}