local builtin = require "telescope.builtin"
local actions = require("telescope.actions") local action_state = require "telescope.actions.state"

-- declare locals for the nvim api stuff to avoid more lsp warnings
local vim = vim


-- ----------------------------------------------------------------------------
-- DEFAULT CONFIG
-- ----------------------------------------------------------------------------
local home = vim.fn.expand("~/zettelkasten")

ZkCfg = {
    home         = home,
    dailies      = home .. '/' .. 'daily',
    weeklies     = home .. '/' .. 'weekly',
    templates    = home .. '/' .. 'templates',
    extension    = ".md",


    -- following a link to a non-existing note will create it
    follow_creates_nonexisting = true,
    dailies_create_nonexisting = true,
    weeklies_create_nonexisting = true,

    -- templates for new notes
    template_new_note   = home .. '/' .. 'templates/new_note.md',
    template_new_daily  = home .. '/' .. 'templates/daily_tk.md',
    template_new_weekly = home .. '/' .. 'templates/weekly_tk.md',

    -- integrate with calendar-vim
    plug_into_calendar = true,
    calendar_opts = {
        -- calendar week display mode: 1 .. 'WK01', 2 .. 'WK 1', 3 .. 'KW01', 4 .. 'KW 1', 5 .. '1'
        weeknm = 4,
        -- use monday as first day of week: 1 .. true, 0 .. false
        calendar_monday = 1,
        -- calendar mark: where to put mark for marked days: 'left', 'right', 'left-fit'
        calendar_mark = 'left-fit',
    }
}

-- ----------------------------------------------------------------------------

local note_type_templates = {
    normal = ZkCfg.template_new_note,
    daily = ZkCfg.template_new_daily,
    weekly = ZkCfg.template_new_weekly,
}

local function file_exists(fname)
   local f=io.open(fname,"r")
   -- print("checking for " .. fname)
   if f~=nil then io.close(f) return true else return false end
end

local function daysuffix(day)
    if((day == '1') or (day == '21') or (day == '31')) then return 'st' end
    if((day == '2') or (day == '22')) then return 'nd' end
    if((day == '3') or (day == '33')) then return 'rd' end
    return 'th'
end

local daymap = { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" }
local monthmap = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" }

local calenderinfo_today = function()
    local dinfo = os.date("*t")
    local opts = {}
    opts.date = os.date("%Y-%m-%d")
    opts.hdate = daymap[dinfo.wday] .. ', ' .. monthmap[dinfo.month] .. ' ' .. dinfo.day .. daysuffix(dinfo.day) .. ', ' .. dinfo.year
    opts.week = os.date("%V")
    opts.month = dinfo.month
    opts.year = dinfo.year
    opts.day = dinfo.day
    return opts
end

local function linesubst(line, title, calendar_info)
    local cinfo = calendar_info or calenderinfo_today()
    local substs = {
        date = cinfo.date,
        hdate = cinfo.hdate,
        week = cinfo.week,
        year = cinfo.year,
        title = title,
    }
    for k, v in pairs(substs) do
        line = line:gsub("{{"..k.."}}", v)
    end

    return line
end

local create_note_from_template = function (title, filepath, templatefn, calendar_info)
    -- first, read the template file
    local lines = {}
    for line in io.lines(templatefn) do
        lines[#lines+1] = line
    end

    -- now write the output file, substituting vars line by line
    local ofile = io.open(filepath, 'a')
    for _, line in pairs(lines) do
        ofile:write(linesubst(line, title, calendar_info) .. '\n')
    end

    ofile:close()
end

local path_to_linkname = function(p)
    local fn = vim.split(p, "/")
    fn = fn[#fn]
    fn = vim.split(fn, ZkCfg.extension)
    fn = fn[1]
    return fn
end


--
-- FindDailyNotes:
-- ---------------
--
-- Select from daily notes
--
FindDailyNotes = function(opts)
    opts = opts or {}

    local today = os.date("%Y-%m-%d")
    local fname = ZkCfg.dailies .. '/' .. today .. ZkCfg.extension
    local fexists = file_exists(fname)
    if ((fexists ~= true) and ((opts.dailies_create_nonexisting == true) or ZkCfg.dailies_create_nonexisting == true)) then
        create_note_from_template(today, fname, note_type_templates.daily)
    end

    builtin.find_files({
        prompt_title = "Find daily note",
        cwd = ZkCfg.dailies,
        find_command = ZkCfg.find_command,
      })
end


--
-- FindWeeklyNotes:
-- ---------------
--
-- Select from daily notes
--
FindWeeklyNotes = function(opts)
    opts = opts or {}

    local title = os.date("%Y-W%V")
    local fname = ZkCfg.weeklies .. '/' .. title .. ZkCfg.extension
    local fexists = file_exists(fname)
    if ((fexists ~= true) and ((opts.weeklies_create_nonexisting == true) or ZkCfg.weeklies_create_nonexisting == true)) then
        create_note_from_template(title, fname, note_type_templates.weekly)
    end

    builtin.find_files({
        prompt_title = "Find weekly note",
        cwd = ZkCfg.weeklies,
        find_command = ZkCfg.find_command,
      })
end


--
-- InsertLink:
-- -----------
--
-- Select from all notes and put a link in the current buffer
--
InsertLink = function(opts)
    opts = opts or {}
    builtin.find_files({
        prompt_title = "Insert link to note",
        cwd = ZkCfg.home,
        attach_mappings = function(prompt_bufnr, map)
            map = map -- get rid of lsp error
            actions.select_default:replace(function()
                actions.close(prompt_bufnr)
                local selection = action_state.get_selected_entry()
                local fn = path_to_linkname(selection.value)
                vim.api.nvim_put({ "[["..fn.."]]" }, "", false, true)
            end)
            return true
        end,
        find_command = ZkCfg.find_command,
   })
end


--
-- FollowLink:
-- -----------
--
-- find the file linked to by the word under the cursor
--
FollowLink = function(opts)
    opts = opts or {}
    vim.cmd('normal yi]')
    local title = vim.fn.getreg('"0')

    -- check if fname exists anywhere
    local fexists = file_exists(ZkCfg.weeklies .. '/' .. title .. ZkCfg.extension)
    fexists = fexists or file_exists(ZkCfg.dailies .. '/' .. title .. ZkCfg.extension)
    fexists = fexists or file_exists(ZkCfg.home .. '/' .. title .. ZkCfg.extension)

    if ((fexists ~= true) and ((opts.follow_creates_nonexisting == true) or ZkCfg.follow_creates_nonexisting == true)) then
        local fname = ZkCfg.home .. '/' .. title .. ZkCfg.extension
        create_note_from_template(title, fname, note_type_templates.normal)
    end

    builtin.find_files({
        prompt_title = "Follow link to note...",
        cwd = ZkCfg.home,
        default_text = title,
        find_command = ZkCfg.find_command,
    })
end


--
-- YankLink:
-- -----------
--
-- Create and yank a [[link]] from the current note.
--
YankLink = function()
    local title = '[[' .. path_to_linkname(vim.fn.expand('%')) .. ']]'
    vim.fn.setreg('"', title)
    print('yanked ' .. title)
end


--
-- GotoToday:
-- ----------
--
-- find today's daily note and create it if necessary.
--


GotoToday = function(opts)
    opts = opts or calenderinfo_today()
    local word = opts.date or os.date("%Y-%m-%d")

    local fname = ZkCfg.dailies .. '/' .. word .. ZkCfg.extension
    local fexists = file_exists(fname)
    if ((fexists ~= true) and ((opts.follow_creates_nonexisting == true) or ZkCfg.follow_creates_nonexisting == true)) then
        create_note_from_template(word, fname, note_type_templates.daily, opts)
    end

    builtin.find_files({
        prompt_title = "Goto day",
        cwd = ZkCfg.home,
        default_text = word,
        find_command = ZkCfg.find_command,
        attach_mappings = function(prompt_bufnr, map)
            map = map -- get rid of lsp error
            actions.select_default:replace(function()
                actions.close(prompt_bufnr)

                -- open the new note
                if (opts.calendar == true) then
                    vim.cmd('wincmd w')
                end
                vim.cmd('e ' .. fname)
            end)
            return true
        end,
    })
end


--
-- FindNotes:
-- ----------
--
-- Select from notes
--
FindNotes = function(opts)
    opts = opts or {}
    builtin.find_files({
        prompt_title = "Find notes by name",
        cwd = ZkCfg.home,
        find_command = ZkCfg.find_command,
   })
end


--
-- SearchNotes:
-- ------------
--
-- find the file linked to by the word under the cursor
--
SearchNotes = function(opts)
    opts = opts or {}

    builtin.live_grep({
        prompt_title = "Search in notes",
        cwd = ZkCfg.home,
        search_dirs = { ZkCfg.home },
        default_text = vim.fn.expand("<cword>"),
        find_command = ZkCfg.find_command,
    })
end


--
-- CreateNote:
-- ------------
--
-- Prompts for title and creates note with default template
--
local function on_create(title)
    if (title == nil) then return end

    local fname = ZkCfg.home .. '/' .. title .. ZkCfg.extension
    local fexists = file_exists(fname)
    if (fexists ~= true) then
        create_note_from_template(title, fname, note_type_templates.normal)
    end

    builtin.find_files({
        prompt_title = "Created note...",
        cwd = ZkCfg.home,
        default_text = title,
        find_command = ZkCfg.find_command,
    })
end

CreateNote = function(opts)
    opts = opts or {}
    vim.ui.input({prompt = 'Title: '}, on_create)
end


--
-- CreateNoteSelectTemplate()
-- --------------------------
--
-- Prompts for title, then pops up telescope for template selection,
-- creates the new note by template and opens it

local function on_create_with_template(title)
    if (title == nil) then return end

    local fname = ZkCfg.home .. '/' .. title .. ZkCfg.extension
    local fexists = file_exists(fname)
    if (fexists == true) then
        -- open the new note
        vim.cmd('e ' .. fname)
        return
    end

    builtin.find_files({
        prompt_title = "Select template...",
        cwd = ZkCfg.templates,
        find_command = ZkCfg.find_command,
        attach_mappings = function(prompt_bufnr, map)
            map = map -- get rid of lsp error
            actions.select_default:replace(function()
                actions.close(prompt_bufnr)
                local template = ZkCfg.templates .. '/' .. action_state.get_selected_entry().value
                create_note_from_template(title, fname, template)
                -- open the new note
                vim.cmd('e ' .. fname)
            end)
            return true
        end,
    })
end

CreateNoteSelectTemplate = function(opts)
    opts = opts or {}
    vim.ui.input({prompt = 'Title: '}, on_create_with_template)
end


--
-- GotoThisWeek:
-- -------------
--
-- find this week's weekly note and create it if necessary.
--
GotoThisWeek = function(opts)
    opts = opts or {}

    local title = os.date("%Y-W%V")
    local fname = ZkCfg.weeklies .. '/' .. title .. ZkCfg.extension
    local fexists = file_exists(fname)
    if ((fexists ~= true) and ((opts.weeklies_create_nonexisting == true) or ZkCfg.weeklies_create_nonexisting == true)) then
        create_note_from_template(title, fname, note_type_templates.weekly)
    end

    builtin.find_files({
        prompt_title = "Goto this week:",
        cwd = ZkCfg.weeklies,
        default_text = title,
        find_command = ZkCfg.find_command,
    })
end



--
-- Calendar Stuff
-- --------------

-- return if a daily 'note exists' indicator (sign) should be displayed for a particular day
CalendarSignDay = function(day, month, year)
    local fn = ZkCfg.dailies .. '/' .. string.format('%04d-%02d-%02d', year, month, day) .. ZkCfg.extension
    if file_exists(fn) then
        return 1
    end
    return 0
end

-- action on enter on a specific day: preview in telescope, stay in calendar on cancel, open note in other window on accept
CalendarAction = function(day, month, year, weekday, dir)
    -- lsp
    dir = dir

    local today = string.format('%04d-%02d-%02d', year, month, day)
    local opts = {}
    opts.date = today
    opts.hdate = daymap[weekday] .. ', ' .. monthmap[tonumber(month)] .. ' ' .. day .. daysuffix(day) .. ', ' .. year
    opts.week = 'n/a'  -- TODO: calculate the week somehow
    opts.month = month
    opts.year = year
    opts.day = day
    opts.calendar = true
    GotoToday(opts)
end

ShowCalendar = function(opts)
    local defaults = {}
    defaults.cmd = 'CalendarVR'
    defaults.vertical_resize = 1

    opts = opts or defaults
    vim.cmd(opts.cmd)
    if (opts.vertical_resize) then
        vim.cmd('vertical resize +' .. opts.vertical_resize)
    end
end

-- set up calendar integration: forward to our lua functions
SetupCalendar = function(opts)
    local defaults = ZkCfg.calendar_opts
    opts = opts or defaults

    local cmd = [[
        function! MyCalSign(day, month, year)
            return luaeval('CalendarSignDay(_A[1], _A[2], _A[3])', [a:day, a:month, a:year])
        endfunction

        function! MyCalAction(day, month, year, weekday, dir)
            " day : day
            " month : month
            " year year 
            " weekday : day of week (monday=1)
            " dir : direction of calendar
            return luaeval('CalendarAction(_A[1], _A[2], _A[3], _A[4], _A[5])', [a:day, a:month, a:year, a:weekday, a:dir]) 
        endfunction

        function! MyCalBegin()
            " too early, windown doesn't exist yet
            " cannot resize
        endfunction

        let g:calendar_sign = 'MyCalSign'
        let g:calendar_action = 'MyCalAction'
        " let g:calendar_begin = 'MyCalBegin'

        let g:calendar_monday = {{calendar_monday}}
        let g:calendar_mark = '{{calendar_mark}}'
        let g:calendar_weeknm = {{weeknm}}
    ]]

    for k, v in pairs(opts) do
        cmd = cmd:gsub('{{' .. k .. '}}', v)
    end
    vim.cmd(cmd)
end


-- Setup(cfg)
--
-- Overrides config with elements from cfg. See top of file for defaults.
--
Setup = function(cfg)
    cfg = cfg or {}
    for k, v in pairs(cfg) do
        -- merge everything but calendar opts
        -- they will be merged later
       if (k ~= 'calendar_opts') then
           ZkCfg[k] = v
       end
    end
    if vim.fn.executable('rg') then
        ZkCfg.find_command = { 'rg', '--files', '--sortr', 'created',  }
    else
        ZkCfg.find_command = nil
    end

    -- this looks a little messy
    if (ZkCfg.plug_into_calendar) then
        cfg.calendar_opts = cfg.calendar_opts or {}
        ZkCfg.calendar_opts = ZkCfg.calendar_opts or {}
        ZkCfg.calendar_opts.weeknm = cfg.calendar_opts.weeknm or ZkCfg.calendar_opts.weeknm or 1
        ZkCfg.calendar_opts.calendar_monday = cfg.calendar_opts.calendar_monday or ZkCfg.calendar_opts.calendar_monday or 1
        ZkCfg.calendar_opts.calendar_mark = cfg.calendar_opts.calendar_mark or ZkCfg.calendar_opts.calendar_mark or 'left-fit'
        SetupCalendar(ZkCfg.calendar_opts)
    end
end

local M = {
    ZkCfg = ZkCfg,
    find_notes = FindNotes,
    find_daily_notes = FindDailyNotes,
    search_notes = SearchNotes,
    insert_link = InsertLink,
    follow_link = FollowLink,
    setup = Setup,
    goto_today = GotoToday,
    new_note = CreateNote,
    goto_thisweek = GotoThisWeek,
    find_weekly_notes = FindWeeklyNotes,
    yank_notelink = YankLink,
    create_note_sel_template = CreateNoteSelectTemplate,
    show_calendar = ShowCalendar,
}
return M