select.lua: select from the watch history with g-h

Implement saving watched paths and selecting them.

--osd-playlist-entry determines whether titles and/or filenames are
shown. But unlike in show-text ${playlist} and select-playlist, "file"
and "both" print full paths because history is much more likely to have
files from completely different directories, so showing the directory
conveys where files are located. This is particularly helpful for
filenames like 1.jpg.

The last entry in the selector deletes the history file, as requested by
Samillion.

The history could be formatted as CSV, but this requires escaping the
separator in the fields and doesn't work with paths and titles with
newlines, or as JSON, but it is inefficient to reread and rewrite the
whole history on each new file, and doing so overwrites the history with
an empty file when writing without disk space left. I went with an
hybrid of one JSON array per line to get the best of both worlds. And I
discovered afterwards that this was an existing thing called NDJSON or
JSONL. Since there are these 2 competing standards it is not clear if
the file extension should be ndjson or jsonl, so I just used txt.

watch_history_path is awkwardly documented along with the key binding
because I don't think it's worth adding a select.lua section to the
manual just for this. I will add it and move it there if I add more
script-opts in the future.

DOCS/man/mpv.rst

@@ -328,6 +328,12 @@ g-l
 g-d
     Select an audio device.
 
+g-h
+    Select a file from the watch history. Requires
+    ``--script-opt=select-save_watch_history=yes``. The history path is
+    configured with ``--script-opt=select-watch_history_path=...``, and defaults
+    to ``~~state/watch_history.txt`` (see `PATHS`_).
+
 g-w
     Select a file from watch later config files (see `RESUMING PLAYBACK`_) to
     resume playing. Requires ``--write-filename-in-watch-later-config``. This

etc/input.conf

@@ -187,6 +187,7 @@
 #g-e script-binding select/select-edition
 #g-l script-binding select/select-subtitle-line
 #g-d script-binding select/select-audio-device
+#g-h script-binding select/select-history
 #g-w script-binding select/select-watch-later
 #g-b script-binding select/select-binding
 #g-r script-binding select/show-properties

player/lua/select.lua

@@ -18,6 +18,13 @@ License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
 local utils = require "mp.utils"
 local input = require "mp.input"
 
+local options = {
+    save_watch_history = false,
+    watch_history_path = "~~state/watch_history.txt",
+}
+
+require "mp.options".read_options(options)
+
 local function show_warning(message)
     mp.msg.warn(message)
     if mp.get_property_native("vo-configured") then
@@ -353,6 +360,92 @@ mp.add_key_binding(nil, "select-audio-device", function ()
     })
 end)
 
+local history_file_path = mp.command_native({"expand-path", options.watch_history_path})
+
+local function save_to_watch_history()
+    local history_file, error_message = io.open(history_file_path, "a")
+    if not history_file then
+        show_error("Failed to write the watch history: " .. error_message)
+        return
+    end
+
+    local path = mp.command_native({"normalize-path", mp.get_property("path")})
+    local title = mp.get_property("playlist/" .. mp.get_property("playlist-pos") .. "/title")
+
+    history_file:write(utils.format_json({os.time(), path, title}) .. "\n")
+    history_file:close()
+end
+
+if options.save_watch_history then
+    mp.register_event("file-loaded", save_to_watch_history)
+end
+
+local function add_history_entry(line, items, paths, osd_playlist_entry)
+    local entry = utils.parse_json(line)
+
+    if not entry then
+        mp.msg.warn(line .. " in " .. history_file_path .. " is not valid JSON.")
+        return
+    end
+
+    local time, path, title = unpack(entry)
+
+    local status, date = pcall(os.date, "(%Y-%m-%d %H:%M) ", time)
+
+    if not status or not path then
+        mp.msg.warn(line .. " in " .. history_file_path .. " has invalid data.")
+        return
+    end
+
+    local item = path
+    if title and osd_playlist_entry == "title" then
+        item = title
+    elseif title and osd_playlist_entry == "both" then
+        item = title .. " (" .. path .. ")"
+    end
+
+    table.insert(items, 1, date .. item)
+    table.insert(paths, 1, path)
+end
+
+mp.add_key_binding(nil, "select-history", function ()
+    local history_file, error_message = io.open(history_file_path)
+    if not history_file then
+        show_warning(options.save_watch_history
+                     and error_message
+                     or "Enable --script-opt=select-save_watch_history=yes")
+        return
+    end
+
+    local items = {}
+    local paths = {}
+    local osd_playlist_entry = mp.get_property("osd-playlist-entry")
+
+    for line in history_file:lines() do
+        add_history_entry(line, items, paths, osd_playlist_entry)
+    end
+
+    items[#items+1] = "Clear the history"
+
+    input.select({
+        prompt = "Select a file:",
+        items = items,
+        submit = function (i)
+            if paths[i] then
+                mp.commandv("loadfile", paths[i])
+                return
+            end
+
+            error_message = select(2, os.remove(history_file_path))
+            if error_message then
+                show_error(error_message)
+            else
+                mp.osd_message("History cleared.")
+            end
+        end,
+    })
+end)
+
 mp.add_key_binding(nil, "select-watch-later", function ()
     local watch_later_dir = mp.get_property("current-watch-later-dir")