dev: Add funding options and Khal Endar module

- Added a new funding.yml file for the GitHub community to support the project.
- Added new Khal Endar lua module in initialization, UI, and utility files.
- The module contains utility functions for calculating dates for various time intervals (week, month, quarter, year).
- The UI file sets up the user interface for the Khal Endar calendar display.
- The initialization file combines these functionalities to show and interact with calendar events.

.github/FUNDING.yml

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+ko_fi: bentribyte
+buy_me_a_coffee: bentribyte

lua/khal_endar/init.lua

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+local M = {}
+M.ui = require("khal_endar.ui")
+M.utils = require("khal_endar.utils")
+local date_funcs = {
+  ["week"] = M.utils.calculate_week_dates,
+  ["month"] = M.utils.calculate_month_dates,
+  ["quarter"] = M.utils.calculate_quarter_dates,
+  ["year"] = M.utils.calculate_year_dates,
+}
+function M.execute_command(command, return_data, print_output)
+  if not return_data or return_data == nil then
+    command = command .. " 2>&1"
+  end
+  local handle = io.popen(command)
+  local result = handle:read("*a")
+  if print_output then
+    print(result)
+  end
+  local _, status, code = handle:close()
+  return code, result
+end
+
+function M.show(type, args)
+  local start_date, end_date = nil, nil
+  if #args == 0 then
+    -- start_date, end_date = M.utils.calculate_relative_datetime('2w')
+    start_date, end_date = M.utils.calculate_week_dates()
+  elseif #args == 1 then
+    if M.utils.table_contains(args[1], { "week", "month", "quarter", "year" }) then
+      start_date, end_date = date_funcs[args[1]]()
+    else
+      start_date, end_date = M.utils.calculate_relative_datetime(args[1])
+    end
+  else
+    start_date, end_date = args[1], args[2]
+  end
+  local _, cal = M.execute_command("khal --color " .. type .. " " .. start_date .. " " .. end_date, true)
+  local contents = vim.split(cal, "\n")
+  M.ui.trigger_hover(contents, "List of events")
+end
+
+function M.run(args)
+  M.execute_command("khal " .. table.concat(args, " "), false, true)
+end
+
+function M.interact()
+  local Popup = require("nui.popup")
+  local event = require("nui.utils.autocmd").event
+
+  local popup = Popup({
+    enter = true,
+    focusable = true,
+    border = {
+      style = "rounded",
+    },
+
+    position = "50%",
+    size = {
+      width = "80%",
+      height = "60%",
+    },
+  })
+
+  -- mount/open the component
+  popup:mount()
+  vim.cmd("term ikhal")
+  vim.cmd("startinsert")
+  popup:on(event.TermClose, function()
+    popup:unmount()
+  end)
+
+end
+
+function M.setup()
+  vim.api.nvim_create_user_command("KLendar", function(args)
+    M.show("calendar", args.fargs)
+  end, { nargs = "*" })
+  vim.api.nvim_create_user_command("KList", function(args)
+    M.show("list", args.fargs)
+  end, { nargs = "*" })
+  vim.api.nvim_create_user_command("KLInteract", function(args)
+    M.interact()
+  end, {})
+  vim.api.nvim_create_user_command("KLRun", function(args)
+    M.run(args.fargs)
+  end, { nargs = "*" })
+
+end
+
+return M

lua/khal_endar/ui.lua

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+local M = {}
+
+function M.trigger_hover(contents, title)
+  if title == nil then
+    title = ""
+  end
+  local Popup = require("nui.popup")
+  local event = require("nui.utils.autocmd").event
+  local autocmd = require("nui.utils.autocmd")
+  local max_width = 0
+  for _, content in ipairs(contents) do
+    max_width = math.max(max_width, #content)
+  end
+  local popup = Popup({
+    enter = false,
+    focusable = true,
+    border = {
+      style = "rounded",
+      text = {
+        top = title,
+        top_align = "center",
+      },
+    },
+    relative = "cursor",
+    position = 0,
+    size = {
+      width = max_width + 1,
+      height = #contents,
+    },
+  })
+
+  -- mount/open the component
+  local bufnr = vim.api.nvim_get_current_buf()
+  autocmd.buf.define(bufnr, { event.CursorMoved, event.BufWinLeave }, function()
+    popup:unmount()
+  end, { once = true })
+  popup:mount()
+
+  vim.api.nvim_buf_set_lines(popup.bufnr, 0, 1, false, contents)
+  vim.api.nvim_buf_set_keymap(popup.bufnr, "n", "q", "<Cmd>q<CR>", { silent = true })
+  vim.api.nvim_buf_call(popup.bufnr, function()
+    vim.cmd("ColorHighlight")
+  end)
+  return popup
+end
+
+return M

lua/khal_endar/utils.lua

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+local M = {}
+
+function M.table_contains(str, tbl)
+    for _, value in ipairs(tbl) do
+        if value == str then
+            return true
+        end
+    end
+    return false
+end
+
+-- Function to check if string_1 is a starting substring of string_2
+function M.starts_with(string, substring)
+    -- Get the substring from string_2 that has the same length as string_1
+    local substring_from_string = string.sub(string, 1, #substring)
+
+    -- Compare the extracted substring with string_1
+    if substring_from_string == substring then
+        return true
+    else
+        return false
+    end
+end
+
+-- Function to calculate start_date and end_date of the current week
+function M.calculate_week_dates()
+    -- Get the current time in seconds since the epoch
+    local current_time = os.time()
+
+    -- Get the current date
+    local current_date = os.date("*t", current_time)
+
+    -- Calculate the day of the week where Monday is 1 and Sunday is 7
+    local weekday = current_date.wday
+    -- Calculate the number of days to subtract to get to the start of the week (Monday)
+    local days_to_subtract = weekday - 2 -- We want Monday to be day 1 (subtract 2 for Sunday)
+    -- Calculate the start date of the week (Monday)
+    local start_date = os.date("*t", current_time - days_to_subtract * 86400)
+    start_date.hour = 0
+    start_date.min = 0
+    start_date.sec = 0
+    -- Calculate the end date of the week (Sunday)
+    local end_date = os.date("*t", current_time + (7 - weekday + 1) * 86400)
+    end_date.hour = 23
+    end_date.min = 59
+    end_date.sec = 59
+    -- Return the start_date and end_date
+    return os.date("%Y-%m-%d", os.time(start_date)), os.date("%Y-%m-%d", os.time(end_date))
+end
+
+function M.calculate_month_dates()
+    -- Get the current time in seconds since the epoch
+    local current_time = os.time()
+
+    -- Get the current date
+    local current_date = os.date("*t", current_time)
+
+    -- Set the day of the current date to 1 to get the start of the month
+    current_date.day = 1
+
+    -- Calculate the start_date of the month
+    local start_date = current_date
+    start_date.hour = 0
+    start_date.min = 0
+    start_date.sec = 0
+
+    -- Calculate the end_date of the month
+    local next_month = start_date.month + 1
+    local next_month_year = start_date.year
+    if next_month > 12 then
+        next_month = 1
+        next_month_year = next_month_year + 1
+    end
+    local end_date = {
+        year = next_month_year,
+        month = next_month,
+        day = 1,
+        hour = 0,
+        min = 0,
+        sec = 0
+    }
+    end_date = os.date("*t", os.time(end_date) - 1) -- Subtract 1 second to get last day of current month
+
+    -- Return the start_date and end_date
+    return os.date("%Y-%m-%d", os.time(start_date)), os.date("%Y-%m-%d", os.time(end_date))
+
+end
+
+function M.calculate_quarter_dates()
+    -- Get the current time in seconds since the epoch
+    local current_time = os.time()
+
+    -- Get the current date
+    local current_date = os.date("*t", current_time)
+
+    -- Determine the current quarter
+    local quarter = math.ceil(current_date.month / 3)
+
+    -- Calculate the start_date of the quarter
+    local start_date = {
+        year = current_date.year,
+        month = (quarter - 1) * 3 + 1,
+        day = 1,
+        hour = 0,
+        min = 0,
+        sec = 0
+    }
+
+    -- Calculate the end_date of the quarter
+    local end_date = {
+        year = current_date.year,
+        month = quarter * 3 + 1,
+        day = 1,
+        hour = 0,
+        min = 0,
+        sec = 0
+    }
+    end_date = os.date("*t", os.time(end_date) - 86400) -- Subtract 1 day to get last day of previous month
+
+    -- Return the start_date and end_date
+    return os.date("%Y-%m-%d", os.time(start_date)), os.date("%Y-%m-%d", os.time(end_date))
+
+end
+
+-- Function to calculate start_date and end_date of the current year
+function M.calculate_year_dates()
+    -- Get the current time in seconds since the epoch
+    local current_time = os.time()
+
+    -- Get the current date
+    local current_date = os.date("*t", current_time)
+
+    -- Calculate the start_date of the year (January 1st of the current year)
+    local start_date = {
+        year = current_date.year,
+        month = 1,
+        day = 1,
+        hour = 0,
+        min = 0,
+        sec = 0
+    }
+
+    -- Calculate the end_date of the year (December 31st of the current year)
+    local end_date = {
+        year = current_date.year,
+        month = 12,
+        day = 31,
+        hour = 23,
+        min = 59,
+        sec = 59
+    }
+
+    -- Return the start_date and end_date
+    return os.date("%Y-%m-%d", os.time(start_date)), os.date("%Y-%m-%d", os.time(end_date))
+
+end
+
+function M.calculate_relative_datetime(interval)
+  -- Parse the interval string to extract the numeric value and unit
+  local numeric_value, unit = interval:match("(%d+)(%a+)")
+  if not numeric_value or not unit then
+    return nil -- Invalid interval format
+  end
+
+  -- Convert numeric value to integer
+  local numeric = tonumber(numeric_value)
+  if not numeric then
+    return nil -- Invalid numeric value
+  end
+
+  -- Get current time in seconds since epoch
+  local now = os.time()
+
+  -- Define time units in seconds
+  local unit_seconds = {
+    ["secconds"] = 1,
+    ["minutes"] = 60,
+    ["hours"] = 3600,
+    ["days"] = 86400,
+    ["weeks"] = 604800, -- 7 days in seconds
+    ["months"] = 2592000, -- 30 days in seconds
+    ["years"] = 31536000, -- 365 days in seconds
+  }
+  for key, _ in pairs(unit_seconds) do
+    if M.starts_with(key, unit) then
+      unit = key
+      break
+    end
+  end
+  -- Calculate the relative time in seconds
+  local interval_seconds = unit_seconds[unit]
+  if not interval_seconds then
+    return nil -- Invalid time unit
+  end
+
+  local relative_time = now + numeric * interval_seconds
+  return 'today', os.date("%Y-%m-%d", relative_time)
+end
+
+
+return M