-- nixos-config - My current NixOS configuration
--
-- Copyright (C) 2025 Benedikt Peetz <benedikt.peetz@b-peetz.de>
-- SPDX-License-Identifier: GPL-3.0-or-later
--
-- This file is part of my nixos-config.
--
-- You should have received a copy of the License along with this program.
-- If not, see <https://www.gnu.org/licenses/gpl-3.0.txt>.

local ls = require("luasnip")
local fmt = require("luasnip.extras.fmt").fmt

--- Get the comment string {begin,end} table
---
---@param comment_type integer 1 for `line`-comment and 2 for `block`-comment
---@return table comment_strings {["begin"]=begin_comment_string, ["end"]=end_comment_string}
local get_comment_string = function(comment_type)
  local calculate_comment_string = require("Comment.ft").calculate
  local utils = require("Comment.utils")

  -- use the `Comments.nvim` API to fetch the comment string for the region (eq. '--%s' or '--[[%s]]' for `lua`)
  local cstring =
    calculate_comment_string({ ctype = comment_type; range = utils.get_region(); })

  if cstring == nil then
    -- TODO: Use `vim.bo.commentstring` <2025-05-02>

    -- Use some useful default values.
    return { ["begin"] = "#"; ["end"] = ""; }
  end

  -- as we want only the strings themselves and not strings ready for using `format` we want to split the left and right side
  local left, right = utils.unwrap_cstr(cstring)

  -- create a `{left, right}` table for it
  return { ["begin"] = left; ["end"] = right; }
end

--- Wraps a table of snippet nodes in two comment function nodes.
---
---@param comment_type integer 1 for `line`-comment and 2 for `block`-comment
---@param nodes table The nodes that should be wrapped
---@return table wrapped_nodes The now wrapped `nodes` table.
local wrap_snippet_in_comments = function(comment_type, nodes)
  local output = {}

  table.insert(output, ls.function_node(function()
    return get_comment_string(comment_type)["begin"]
  end))


  for _, v in ipairs(nodes) do
    table.insert(output, v)
  end

  table.insert(output, ls.function_node(function()
    return get_comment_string(comment_type)["end"]
  end))

  return output
end

-- auto_pairs  {{{
local get_visual = function(_, parent)
  if #parent.snippet.env.SELECT_RAW > 0 then
    return ls.snippet_node(nil, ls.insert_node(1, parent.snippet.env.SELECT_RAW))
  else
    return ls.snippet_node(nil, ls.insert_node(1, ""))
  end
end

local function char_count_same(c1, c2)
  local line = vim.api.nvim_get_current_line()
  -- '%'-escape chars to force explicit match (gsub accepts patterns).
  -- second return value is number of substitutions.
  local _, ct1 = string.gsub(line, "%" .. c1, "")
  local _, ct2 = string.gsub(line, "%" .. c2, "")
  return ct1 == ct2
end

local function even_count(c, ...)
  local line = vim.api.nvim_get_current_line()
  local _, ct = string.gsub(line, c, "")
  return ct % 2 == 0
end

-- This makes creation of pair-type snippets easier.
local function pair(pair_begin, pair_end, file_types, condition_function)
  -- FIXME(@Soispha): This only works if file_types == nil, otherwise the snippet does not expand.
  -- It would be nice, if it would support both an empty array (`{}`) and nil <2023-08-27>
  -- file_types = file_types or {};

  return ls.snippet(
    {
      trig = pair_begin;
      wordTrig = false;
      snippetType = "autosnippet";
    },
    {
      ls.text_node({ pair_begin; });
      ls.dynamic_node(1, get_visual);
      ls.text_node({ pair_end; });
    },
    {
      condition = function()
        local filetype_check = true

        if file_types ~= nil then
          filetype_check = file_types[vim.bo.filetype] or false
        end

        return (not condition_function(pair_begin, pair_end)) and filetype_check
      end;
    }
  )
end

local auto_pairs = {
  pair("(", ")", nil, char_count_same);
  pair("{", "}", nil, char_count_same);
  pair("[", "]", nil, char_count_same);
  pair("<", ">", { ["rust"] = true; ["tex"] = true; }, char_count_same);
  pair("'", "'", nil, even_count);
  pair("\"", "\"", nil, even_count);
  pair("`", "`", nil, even_count);
}

ls.add_snippets("all", auto_pairs, { type = "snippets"; key = "auto_pairs"; })
-- }}}

-- todo_comments {{{
local read_git_config = function(config_value)
  local command = string.format("git config \"%s\"", config_value)

  local handle = io.popen(command)
  if handle == nil then
    return error(string.format("Failed to call `%s`.", command))
  end

  local result = handle:read("*a")
  handle:close()

  -- stripped = string.gsub(str, '%s+', '')
  return string.gsub(result, "\n", "")
end

--- Create a @handle from a full name.
---
--- Example:
--- “Benedikt Peetz” -> “@bpeetz”
local handle_from_name = function(name)
  -- from: https://stackoverflow.com/a/7615129
  local split = function(inputstr, sep)
    local t = {}
    for str in string.gmatch(inputstr, "([^" .. sep .. "]+)") do
      table.insert(t, str)
    end
    return t
  end

  -- Split on spaces
  local parts = split(name, "%s")

  local output_name = ""

  if #parts > 2 then
    -- Only use the first chars.
    --
    -- Example:
    -- “Richard Matthew Stallman” -> “rms”
    for _, val in ipairs(parts) do
      output_name = string.format("%s%s", output_name, val:sub(1, 1))
    end
  elseif #parts == 2 then
    output_name = string.format("%s%s", parts[1]:sub(1, 1), parts[2])
  elseif #parts == 1 then
    output_name = parts[1]
  elseif #parts == 0 then
    output_name = "<NoName>"
  end

  return string.format("@%s", output_name:lower())
end

--- Generate a comment snippet
---
---@param trig string The trigger
---@param name string name for the comment (ex.: {FIX, ISSUE, FIXIT, BUG})
---@param comment_type integer The comment type.
---@param mark_function function: The function used to get the marks
local todo_snippet = function(trig, name, comment_type, mark_function)
  assert(trig, "context doesn't include a `trig` key which is mandatory")
  assert(comment_type == 1 or comment_type == 2)

  local context = {}
  context.name = name .. " comment"
  context.trig = trig

  local date_node, signature_node = mark_function()

  local nodes = fmt("{} {}{}: {} {} {}", wrap_snippet_in_comments(comment_type, {
    ls.text_node(name);
    signature_node;
    ls.insert_node(1, "content");
    date_node;
  }))

  return ls.snippet(context, nodes, { ctype = comment_type; })
end

---@param trigger string: The luasnip trigger
---@param comment_type integer: The luasnip comment type
---@param name string: All aliases for a name
---@return table: All possible snippets build from the marks
local process_marks = function(trigger, name, comment_type)
  local username = function()
    return handle_from_name(read_git_config("user.name"))
  end

  local marks = {
    signature = function()
      return ls.text_node("(" .. username() .. ")"), ls.text_node("")
    end;

    date_signature = function()
      return ls.text_node("<" .. os.date("%Y-%m-%d") .. ">"), ls.text_node("(" .. username() .. ")")
    end;

    date = function()
      return ls.text_node("<" .. os.date("%Y-%m-%d") .. ">"), ls.text_node("")
    end;

    empty = function()
      return ls.text_node(""), ls.text_node("")
    end;
  }

  local output = {}
  for mark_name, mark_function in pairs(marks) do
    local trig = trigger .. "-" .. mark_name

    output[#output + 1] = todo_snippet(trig, name, comment_type, mark_function)
  end

  return output
end

local todo_snippet_specs = {
  { { trig = "todo"; };  { "TODO"; };                                     { ctype = 1; }; };
  { { trig = "fix"; };   { "FIXME"; "ISSUE"; };                           { ctype = 1; }; };
  { { trig = "hack"; };  { "HACK"; };                                     { ctype = 1; }; };
  { { trig = "warn"; };  { "WARNING"; };                                  { ctype = 1; }; };
  { { trig = "perf"; };  { "PERFORMANCE"; "OPTIMIZE"; };                  { ctype = 1; }; };
  { { trig = "note"; };  { "NOTE"; "INFO"; };                             { ctype = 1; }; };

  -- NOTE: Block commented todo-comments
  { { trig = "todob"; }; { "TODO"; };                                     { ctype = 2; }; };
  { { trig = "fixb"; };  { "FIXME"; "ISSUE"; };                           { ctype = 2; }; };
  { { trig = "hackb"; }; { "HACK"; };                                     { ctype = 2; }; };
  { { trig = "warnb"; }; { "WARNING"; };                                  { ctype = 2; }; };
  { { trig = "perfb"; }; { "PERF"; "PERFORMANCE"; "OPTIM"; "OPTIMIZE"; }; { ctype = 2; }; };
  { { trig = "noteb"; }; { "NOTE"; "INFO"; };                             { ctype = 2; }; };
}

local todo_comment_snippets = {}
for _, v in ipairs(todo_snippet_specs) do
  local snippets = process_marks(v[1].trig, v[2][1], v[3].ctype)
  for _, value in pairs(snippets) do
    table.insert(todo_comment_snippets, value)
  end
end

ls.add_snippets("all", todo_comment_snippets, { type = "snippets"; key = "todo_comments"; })
-- }}}

-- spdx snippets {{{
local generate_spdx_snippet = function(comment_type, spdx_license_expr, trigger)
  assert(trigger, "context doesn't include a `trig` key which is mandatory")
  assert(comment_type == 1 or comment_type == 2)

  local context = {}
  context.name = trigger .. " spdx snippet expr"
  context.trig = trigger


  local nodes = {
    fmt("{} SPDX-SnippetBegin {}", wrap_snippet_in_comments(comment_type, {}));

    fmt("{} SPDX-SnippetCopyrightText: {} {} <{}> {}",
        wrap_snippet_in_comments(comment_type, {
          ls.insert_node(1, "year");
          ls.insert_node(2, "author");
          ls.insert_node(3, "email");
        })
    );

    fmt("{} SPDX-License-Identifier: {} {}", wrap_snippet_in_comments(comment_type, {
      ls.text_node(spdx_license_expr);
    }));

    { ls.insert_node(4, "content"); };

    fmt("{} SPDX-SnippetEnd {}", wrap_snippet_in_comments(comment_type, {}));

    { ls.insert_node(0); };
  }

  local newline_nodes = {}
  for _, sub_nodes in ipairs(nodes) do
    for _, node in ipairs(sub_nodes) do
      table.insert(newline_nodes, node)
    end

    -- luasnip requires newlines to be encoded like this:
    table.insert(newline_nodes, ls.text_node({ ""; ""; }))
  end

  return ls.snippet(context, newline_nodes, { ctype = comment_type; })
end

local spdx = {
  { trigger = "spdx-AGPL3+"; license = "AGPL-3.0-or-later"; };
  { trigger = "spdx-GPL3+";  license = "GPL-3.0-or-later"; };
  { trigger = "spdx-MIT";    license = "MIT"; };
}

local spdx_snippets = {}
for _, value in ipairs(spdx) do
  local snippet = generate_spdx_snippet(1, value.license, value.trigger)
  table.insert(spdx_snippets, snippet)

  snippet = generate_spdx_snippet(2, value.license, value.trigger .. "-block")
  table.insert(spdx_snippets, snippet)
end

ls.add_snippets("all", spdx_snippets, { type = "snippets"; key = "spdx_snippets"; })
-- }}}