feat(core.ui.calendar): implement more of the barebones UI

lua/neorg/modules/core/ui/calendar.lua

@@ -32,11 +32,9 @@ module.public = {
 
             -- Next, we need two namespaces: one for rendering decorational
             -- extmarks, and one for logical operations.
-            -- TODO: Break out the logical namespace into a separate `do` block?
-            local decorational_namespace, logical_namespace = vim.api.nvim_create_namespace("neorg/calendar/decorational"), vim.api.nvim_create_namespace("neorg/calendar/logical")
+            local decorational_namespace = vim.api.nvim_create_namespace("neorg/calendar/decorational")
 
             vim.api.nvim_buf_clear_namespace(buffer, decorational_namespace, 0, -1)
-            vim.api.nvim_buf_clear_namespace(buffer, logical_namespace, 0, -1)
 
             --> Decorational section
             -- CALENDAR text:
@@ -56,6 +54,55 @@ module.public = {
                 virt_text_pos = "overlay"
             })
         end
+
+        local logical_namespace = vim.api.nvim_create_namespace("neorg/calendar/logical")
+
+        vim.api.nvim_buf_clear_namespace(buffer, logical_namespace, 0, -1)
+
+        local year, month, day = os.date("%Y-%m-%d"):match("(%d+)%-(%d+)%-(%d+)")
+
+        -- Display the current year
+        local year_extmark = vim.api.nvim_buf_set_extmark(buffer, logical_namespace, 2, half_width - math.floor(string.len("< " .. tostring(year) .. " >") / 2), {
+            virt_text = { { "< ", "Whitespace" }, { tostring(year), "TSNumber" }, { " >", "Whitespace" } },
+            virt_text_pos = "overlay",
+        })
+
+        --> Month rendering routine
+        -- We render the first month at the very center of the screen. Each month takes up a static 26 characters.
+
+        -- Render the top text of the month (June, August etc.)
+        -- The top text displays the abbreviated month
+        -- TODO: Extract this logic out into a function because different views
+        -- will supply different abbreviations to render.
+        local abbreviated_month_name = os.date("%b", os.time({
+            year = year,
+            month = month,
+            day = day,
+        }))
+
+        vim.api.nvim_buf_set_extmark(buffer, logical_namespace, 4, half_width - math.floor(string.len(abbreviated_month_name) / 2), {
+            virt_text = { { abbreviated_month_name, "TSUnderline" } },
+            virt_text_pos = "overlay",
+        })
+
+        -- Render the days of the week
+        -- To effectively do this, we grab all the weekdays from a constant time.
+        -- This makes the weekdays retrieved locale dependent (which is what we want).
+        local weekdays = {}
+
+        for i = 1, 7 do
+            table.insert(weekdays, { os.date("%a", os.time({
+                year = 2000,
+                month = 5,
+                day = i,
+            })):sub(1, 1), "TSTitle" })
+            table.insert(weekdays, { " " })
+        end
+
+        vim.api.nvim_buf_set_extmark(buffer, logical_namespace, 5, half_width - math.floor(#weekdays / 2) + 1, {
+            virt_text = weekdays,
+            virt_text_pos = "overlay",
+        })
     end,
 
     select_date = function(options)