(*---------------------------------------------------------------------------
   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
    Fmt.str "%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
    Fmt.str "%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 -> Fmt.str "[%s](%s)" repo url
  | None -> repo (* No URL available, just use repo name *)

let format_entry_zulip buf (entry : Changes_aggregated.entry) =
  let repo_link = format_repo_link entry.repository entry.repo_url in
  Buffer.add_string buf (Fmt.str "**%s**: %s\n" repo_link entry.summary);
  List.iter
    (fun change -> Buffer.add_string buf (Fmt.str "- %s\n" change))
    entry.changes;
  if entry.contributors <> [] then
    Buffer.add_string buf
      (Fmt.str "*Contributors: %s*\n" (String.concat ", " entry.contributors));
  Buffer.add_string buf "\n"

let format_type_section buf title entries =
  if entries <> [] then begin
    Buffer.add_string buf (Fmt.str "### %s\n\n" title);
    List.iter (format_entry_zulip buf) entries
  end

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
      Buffer.add_string buf
        (match date with
        | Some d -> Fmt.str "Updates for %s:\n\n" d
        | None -> "Recent updates:\n\n");
    (* 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
    List.iter
      (fun (ct, title) ->
        let matching =
          List.filter
            (fun (e : Changes_aggregated.entry) -> e.change_type = ct)
            entries
        in
        format_type_section buf title matching)
      by_type;
    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
    Fmt.str "%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_entry buf (entry : Changes_daily.entry) =
  Buffer.add_string buf (Fmt.str "**%s**\n" entry.summary);
  List.iter
    (fun change -> Buffer.add_string buf (Fmt.str "- %s\n" change))
    entry.changes;
  if entry.contributors <> [] then
    Buffer.add_string buf
      (Fmt.str "*Contributors: %s*\n" (String.concat ", " entry.contributors));
  Buffer.add_string buf "\n"

let format_repo_section buf repo repo_entries =
  if repo_entries <> [] then begin
    let first_entry = List.hd repo_entries in
    let repo_link = format_repo_link repo first_entry.Changes_daily.repo_url in
    Buffer.add_string buf (Fmt.str "### %s\n\n" repo_link);
    List.iter (format_daily_entry buf) repo_entries
  end

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
      Buffer.add_string buf
        (match date with
        | Some d -> Fmt.str "## Changes for %s\n\n" d
        | None -> "## Recent Changes\n\n");
    (* 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
        format_repo_section buf repo repo_entries)
      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
    Fmt.str "%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)