local M = {}

local query = vim.treesitter.query.parse(
  "lua",
  [[
    ;; top-level locals
    ((variable_declaration (
      assignment_statement 
        (variable_list name: (identifier) @local_name)
        (expression_list value: (_) @local_value)
        (#match? @local_value "(setmetatable|\\{)")
      )) @local
      (#any-of? @local_name "M" "defaults" "config")
      (#has-parent? @local chunk))

    ;; top-level functions/methods
    (function_declaration 
      name: (_) @fun_name (#match? @fun_name "^M")
      parameters: (_) @fun_params
    ) @fun

    ;; styles
    (function_call
      name: (dot_index_expression) @_sf (#eq? @_sf "Snacks.config.style")
      arguments: (arguments
        (string content: (string_content) @style_name)
        (table_constructor) @style_config)
    ) @style
  ]]
)

---@class snacks.docs.Capture
---@field name string
---@field line number
---@field node TSNode
---@field text string
---@field comment string
---@field fields table<string, string>

---@class snacks.docs.Parse
---@field captures snacks.docs.Capture[]
---@field comments string[]

---@class snacks.docs.Info
---@field config? string
---@field mod? string
---@field methods {name: string, args: string, comment?: string, types?: string, type: "method"|"function"}[]
---@field types string[]
---@field styles {name:string, opts:string}[]

---@param lines string[]
function M.parse(lines)
  local source = table.concat(lines, "\n")
  local parser = vim.treesitter.get_string_parser(source, "lua")
  parser:parse()

  local comments = {} ---@type string[]
  for l, line in ipairs(lines) do
    if line:find("^%-%-") then
      comments[l] = line
      if comments[l - 1] then
        comments[l] = comments[l - 1] .. "\n" .. comments[l]
        comments[l - 1] = nil
      end
    end
  end

  ---@type snacks.docs.Parse
  local ret = { captures = {}, comments = {} }

  for id, node in query:iter_captures(parser:trees()[1]:root(), source) do
    local name = query.captures[id]
    if not name:find("_") then
      -- add fields
      local fields = {}
      for id2, node2 in query:iter_captures(node, source) do
        local c = query.captures[id2]
        if c:find(".+_") then
          fields[c:gsub("^.*_", "")] = vim.treesitter.get_node_text(node2, source)
        end
      end

      -- add comments
      local comment = "" ---@type string
      if comments[node:start()] then
        comment = comments[node:start()]
        comments[node:start()] = nil
      end

      table.insert(ret.captures, {
        text = vim.treesitter.get_node_text(node, source),
        name = name,
        comment = comment,
        line = node:start() + 1,
        node = node,
        fields = fields,
      })
    end
  end

  -- remove comments that are followed by code
  for l in pairs(comments) do
    if lines[l + 1] and lines[l + 1]:find("^.+$") then
      comments[l] = nil
    end
  end
  for l in ipairs(lines) do
    if comments[l] then
      table.insert(ret.comments, comments[l])
    end
  end

  return ret
end

---@param lines string[]
function M.extract(lines)
  local parse = M.parse(lines)
  ---@type snacks.docs.Info
  local ret = {
    methods = {},
    types = vim.tbl_filter(function(c)
      return not c:find("@private")
    end, parse.comments),
    styles = {},
  }

  for _, c in ipairs(parse.captures) do
    if c.comment:find("@private") then
      -- skip private
    elseif c.name == "local" then
      if vim.tbl_contains({ "defaults", "config" }, c.fields.name) then
        ret.config = vim.trim(c.comment .. "\n" .. c.fields.value)
      elseif c.fields.name == "M" then
        ret.mod = c.comment
      end
    elseif c.name == "fun" then
      local name = c.fields.name:sub(2)
      local args = (c.fields.params or ""):sub(2, -2)
      local comment = c.comment
      local type = name:sub(1, 1)
      name = name:sub(2)
      if not name:find("^_") then
        table.insert(ret.methods, { name = name, args = args, comment = comment, type = type })
      end
    elseif c.name == "style" then
      table.insert(ret.styles, { name = c.fields.name, opts = c.fields.config })
    end
  end

  return ret
end

---@param tag string
---@param readme string
---@param content string
function M.replace(tag, readme, content)
  content = vim.trim(content)
  local pattern = "(<%!%-%- " .. tag .. ":start %-%->).*(<%!%-%- " .. tag .. ":end %-%->)"
  if not readme:find(pattern) then
    error("tag " .. tag .. " not found")
  end
  return readme:gsub(pattern, "%1\n\n" .. content .. "\n\n%2")
end

---@param str string
---@param opts? {extract_comment: boolean} -- default true
function M.md(str, opts)
  str = str or ""
  opts = opts or {}
  if opts.extract_comment == nil then
    opts.extract_comment = true
  end
  str = str:gsub("\n%s*%-%-%s*stylua: ignore\n", "\n")
  local comments = {} ---@type string[]
  local lines = vim.split(str, "\n", { plain = true })

  if opts.extract_comment then
    while lines[1] and lines[1]:find("^%-%-") and not lines[1]:find("^%-%-%-%s*@") do
      local line = table.remove(lines, 1):gsub("^[%-]*%s*", "")
      table.insert(comments, line)
    end
  end

  local ret = {} ---@type string[]
  if #comments > 0 then
    table.insert(ret, vim.trim(table.concat(comments, "\n")))
    table.insert(ret, "")
  end
  if #lines > 0 then
    table.insert(ret, "```lua")
    table.insert(ret, vim.trim(table.concat(lines, "\n")))
    table.insert(ret, "```")
  end

  return vim.trim(table.concat(ret, "\n")) .. "\n"
end

---@param name string
---@param info snacks.docs.Info
function M.render(name, info)
  local lines = {} ---@type string[]
  local function add(line)
    table.insert(lines, line)
  end

  local prefix = ("Snacks.%s"):format(name)
  if name == "init" then
    prefix = "Snacks"
  end

  if info.config then
    add("## ⚙️ Config\n")
    add(M.md(info.config))
  end

  if #info.styles > 0 then
    table.sort(info.styles, function(a, b)
      return a.name < b.name
    end)
    add("## 🎨 Styles\n")
    for _, style in pairs(info.styles) do
      add(("### `%s`\n"):format(style.name))
      add(M.md(style.opts))
    end
  end

  if #info.types > 0 then
    add("## 📚 Types\n")
    for _, t in ipairs(info.types) do
      add(M.md(t))
    end
  end

  if info.mod or #info.methods > 0 then
    add("## 📦 Module\n")
  end

  if info.mod then
    local mod_lines = vim.split(info.mod, "\n")
    mod_lines = vim.tbl_filter(function(line)
      local overload = line:match("^%-%-%-%s*@overload (.*)(%s*)$") --[[@as string?]]
      if overload then
        table.insert(info.methods, {
          name = "",
          args = "",
          type = "",
          comment = "---@type " .. overload,
        })
        return false
      elseif line:find("^%s*$") then
        return false
      end
      return true
    end, mod_lines)
    local hide = #mod_lines == 1 and mod_lines[1]:find("@class")
    if not hide then
      table.insert(mod_lines, prefix .. " = {}")
      add(M.md(table.concat(mod_lines, "\n")))
    end
  end

  table.sort(info.methods, function(a, b)
    if a.type == b.type then
      return a.name < b.name
    end
    return a.type < b.type
  end)

  for _, method in ipairs(info.methods) do
    add(("### `%s%s%s()`\n"):format(method.type == ":" and name or prefix, method.type, method.name))
    local code = ("%s\n%s%s%s(%s)"):format(
      method.comment or "",
      method.type == ":" and name or prefix,
      method.type,
      method.name,
      method.args
    )
    add(M.md(code))
  end

  lines = vim.split(vim.trim(table.concat(lines, "\n")), "\n")
  return lines
end

function M.write(name, lines)
  local path = ("docs/%s.md"):format(name)
  local ok, text = pcall(vim.fn.readfile, path)

  local docgen = "<!-- docgen -->"
  local top = {} ---@type string[]

  if not ok then
    table.insert(top, "# 🍿 " .. name)
    table.insert(top, "")
  else
    for _, line in ipairs(text) do
      if line == docgen then
        break
      end
      table.insert(top, line)
    end
  end
  table.insert(top, docgen)
  table.insert(top, "")
  vim.list_extend(top, lines)

  vim.fn.writefile(top, path)
end

function M._build()
  local skip = { "docs", "health" }
  for file, t in vim.fs.dir("lua/snacks", { depth = 1 }) do
    local name = vim.fn.fnamemodify(file, ":t:r")
    if t == "file" and not vim.tbl_contains(skip, name) then
      print(name .. ".md")
      local path = ("lua/snacks/%s"):format(file)
      local lines = vim.fn.readfile(path)
      local info = M.extract(lines)
      M.write(name, M.render(name, info))
      if name == "init" then
        local readme = table.concat(vim.fn.readfile("README.md"), "\n")
        local example = table.concat(vim.fn.readfile("docs/example.lua"), "\n")
        example = example:gsub(".*\nreturn {", "{", 1)
        readme = M.replace("config", readme, M.md(info.config))
        readme = M.replace("example", readme, M.md(example))
        vim.fn.writefile(vim.split(readme, "\n"), "README.md")
      end
    end
  end
  vim.cmd.checktime()
end

function M.fix_titles()
  for file, t in vim.fs.dir("doc", { depth = 1 }) do
    if t == "file" and file:find("%.txt$") then
      local lines = vim.fn.readfile("doc/" .. file) --[[@as string[] ]]
      for i, line in ipairs(lines) do
        -- Example: SNACKS.GIT.BLAME_LINE()            *snacks-git-module-snacks.git.blame_line()*
        local func = line:gsub("^SNACKS.*module%-snacks(.+%(%))%*$", "Snacks%1")
        if func ~= line then
          local left = ("`%s`"):format(func)
          local right = ("*%s*"):format(func)
          line = left .. string.rep(" ", #line - #left - #right) .. right
          lines[i] = line
        end
      end
      vim.fn.writefile(lines, "doc/" .. file)
    end
  end
  vim.cmd.helptags("doc")
end

function M.build()
  local ok, err = pcall(M._build)
  if not ok then
    vim.api.nvim_err_writeln(err)
    os.exit(1)
  end
end

return M