(*---------------------------------------------------------------------------
   Copyright (c) 2026 Anil Madhavapeddy <anil@recoil.org>. All rights reserved.
   SPDX-License-Identifier: ISC
  ---------------------------------------------------------------------------*)

(** High-level query interface for changes.

    This module provides convenient functions for querying changes since a
    specific timestamp and formatting them for broadcast. *)

let changes_since ~fs ~changes_dir ~since ~now =
  (* Get the date part of since for filtering *)
  let since_date =
    let (y, m, d), _ = Ptime.to_date_time since in
    Printf.sprintf "%04d-%02d-%02d" y m d
  in
  (* Get current date for range end *)
  let now_date =
    let (y, m, d), _ = Ptime.to_date_time now in
    Printf.sprintf "%04d-%02d-%02d" y m d
  in
  match
    Changes_aggregated.load_range ~fs ~changes_dir ~from_date:since_date
      ~to_date:now_date
  with
  | Error e -> Error e
  | Ok aggregated_files ->
      (* Filter to files generated after 'since' and collect entries *)
      let entries =
        List.concat_map
          (fun (agg : Changes_aggregated.t) ->
            if Ptime.compare agg.generated_at since > 0 then agg.entries else [])
          aggregated_files
      in
      Ok entries

let has_new_changes ~fs ~changes_dir ~since ~now =
  match changes_since ~fs ~changes_dir ~since ~now with
  | Ok entries -> entries <> []
  | Error _ -> false

let format_repo_link repo url_opt =
  match url_opt with
  | Some url -> Printf.sprintf "[%s](%s)" repo url
  | None -> repo (* No URL available, just use repo name *)

let format_for_zulip ~entries ~include_date ~date =
  if entries = [] then "No changes to report."
  else begin
    let buf = Buffer.create 1024 in
    if include_date then begin
      match date with
      | Some d -> Buffer.add_string buf (Printf.sprintf "Updates for %s:\n\n" d)
      | None -> Buffer.add_string buf "Recent updates:\n\n"
    end;
    (* Group by change type *)
    let by_type =
      [
        (Changes_aggregated.New_library, "New Libraries", []);
        (Changes_aggregated.Feature, "Features", []);
        (Changes_aggregated.Bugfix, "Bug Fixes", []);
        (Changes_aggregated.Documentation, "Documentation", []);
        (Changes_aggregated.Refactor, "Improvements", []);
        (Changes_aggregated.Unknown, "Other Changes", []);
      ]
    in
    let grouped =
      List.map
        (fun (ct, title, _) ->
          let matching =
            List.filter
              (fun (e : Changes_aggregated.entry) -> e.change_type = ct)
              entries
          in
          (ct, title, matching))
        by_type
    in
    List.iter
      (fun (_ct, title, entries) ->
        if entries <> [] then begin
          Buffer.add_string buf (Printf.sprintf "### %s\n\n" title);
          List.iter
            (fun (entry : Changes_aggregated.entry) ->
              let repo_link =
                format_repo_link entry.repository entry.repo_url
              in
              Buffer.add_string buf
                (Printf.sprintf "**%s**: %s\n" repo_link entry.summary);
              List.iter
                (fun change ->
                  Buffer.add_string buf (Printf.sprintf "- %s\n" change))
                entry.changes;
              if entry.contributors <> [] then
                Buffer.add_string buf
                  (Printf.sprintf "*Contributors: %s*\n"
                     (String.concat ", " entry.contributors));
              Buffer.add_string buf "\n")
            entries
        end)
      grouped;
    Buffer.contents buf
  end

let format_summary ~entries =
  if entries = [] then "No new changes."
  else
    let count = List.length entries in
    let repos =
      List.sort_uniq String.compare
        (List.map (fun (e : Changes_aggregated.entry) -> e.repository) entries)
    in
    Printf.sprintf "%d change%s across %d repositor%s: %s" count
      (if count = 1 then "" else "s")
      (List.length repos)
      (if List.length repos = 1 then "y" else "ies")
      (String.concat ", " repos)

(** {1 Daily Changes (Real-time)} *)

let daily_changes_since ~fs ~changes_dir ~since =
  Changes_daily.entries_since ~fs ~changes_dir ~since

let has_new_daily_changes ~fs ~changes_dir ~since =
  daily_changes_since ~fs ~changes_dir ~since <> []

let format_daily_for_zulip ~entries ~include_date ~date =
  if entries = [] then "No changes to report."
  else begin
    let buf = Buffer.create 1024 in
    if include_date then begin
      match date with
      | Some d ->
          Buffer.add_string buf (Printf.sprintf "## Changes for %s\n\n" d)
      | None -> Buffer.add_string buf "## Recent Changes\n\n"
    end;
    (* Group by repository *)
    let repos =
      List.sort_uniq String.compare
        (List.map (fun (e : Changes_daily.entry) -> e.repository) entries)
    in
    List.iter
      (fun repo ->
        let repo_entries =
          List.filter
            (fun (e : Changes_daily.entry) -> e.repository = repo)
            entries
        in
        if repo_entries <> [] then begin
          let first_entry = List.hd repo_entries in
          let repo_link = format_repo_link repo first_entry.repo_url in
          Buffer.add_string buf (Printf.sprintf "### %s\n\n" repo_link);
          List.iter
            (fun (entry : Changes_daily.entry) ->
              Buffer.add_string buf (Printf.sprintf "**%s**\n" entry.summary);
              List.iter
                (fun change ->
                  Buffer.add_string buf (Printf.sprintf "- %s\n" change))
                entry.changes;
              if entry.contributors <> [] then
                Buffer.add_string buf
                  (Printf.sprintf "*Contributors: %s*\n"
                     (String.concat ", " entry.contributors));
              Buffer.add_string buf "\n")
            repo_entries
        end)
      repos;
    Buffer.contents buf
  end

let format_daily_summary ~entries =
  if entries = [] then "No new changes."
  else
    let count = List.length entries in
    let repos =
      List.sort_uniq String.compare
        (List.map (fun (e : Changes_daily.entry) -> e.repository) entries)
    in
    Printf.sprintf "%d change%s across %d repositor%s: %s" count
      (if count = 1 then "" else "s")
      (List.length repos)
      (if List.length repos = 1 then "y" else "ies")
      (String.concat ", " repos)