local api = vim.api
local query = vim.treesitter.query
local Range = require('vim.treesitter._range')

local ns = api.nvim_create_namespace('treesitter/highlighter')

---@alias vim.treesitter.highlighter.Iter fun(end_line: integer|nil): integer, TSNode, TSMetadata

---@class vim.treesitter.highlighter.Query
---@field private _query vim.treesitter.query.Query?
---@field private lang string
---@field private hl_cache table<integer,integer>
local TSHighlighterQuery = {}
TSHighlighterQuery.__index = TSHighlighterQuery

---@private
---@param lang string
---@param query_string string?
---@return vim.treesitter.highlighter.Query
function TSHighlighterQuery.new(lang, query_string)
  local self = setmetatable({}, TSHighlighterQuery)
  self.lang = lang
  self.hl_cache = {}

  if query_string then
    self._query = query.parse(lang, query_string)
  else
    self._query = query.get(lang, 'highlights')
  end

  return self
end

---@package
---@param capture integer
---@return integer?
function TSHighlighterQuery:get_hl_from_capture(capture)
  if not self.hl_cache[capture] then
    local name = self._query.captures[capture]
    local id = 0
    if not vim.startswith(name, '_') then
      id = api.nvim_get_hl_id_by_name('@' .. name .. '.' .. self.lang)
    end
    self.hl_cache[capture] = id
  end

  return self.hl_cache[capture]
end

---@package
function TSHighlighterQuery:query()
  return self._query
end

---@class vim.treesitter.highlighter.State
---@field tstree TSTree
---@field next_row integer
---@field iter vim.treesitter.highlighter.Iter?
---@field highlighter_query vim.treesitter.highlighter.Query

---@class vim.treesitter.highlighter
---@field active table<integer,vim.treesitter.highlighter>
---@field bufnr integer
---@field orig_spelloptions string
--- A map of highlight states.
--- This state is kept during rendering across each line update.
---@field _highlight_states vim.treesitter.highlighter.State[]
---@field _queries table<string,vim.treesitter.highlighter.Query>
---@field tree LanguageTree
---@field redraw_count integer
local TSHighlighter = {
  active = {},
}

TSHighlighter.__index = TSHighlighter

---@package
---
--- Creates a highlighter for `tree`.
---
---@param tree LanguageTree parser object to use for highlighting
---@param opts (table|nil) Configuration of the highlighter:
---           - queries table overwrite queries used by the highlighter
---@return vim.treesitter.highlighter Created highlighter object
function TSHighlighter.new(tree, opts)
  local self = setmetatable({}, TSHighlighter)

  if type(tree:source()) ~= 'number' then
    error('TSHighlighter can not be used with a string parser source.')
  end

  opts = opts or {} ---@type { queries: table<string,string> }
  self.tree = tree
  tree:register_cbs({
    on_bytes = function(...)
      self:on_bytes(...)
    end,
    on_detach = function()
      self:on_detach()
    end,
  })

  tree:register_cbs({
    on_changedtree = function(...)
      self:on_changedtree(...)
    end,
    on_child_removed = function(child)
      child:for_each_tree(function(t)
        self:on_changedtree(t:included_ranges(true))
      end)
    end,
  }, true)

  local source = tree:source()
  assert(type(source) == 'number')

  self.bufnr = source
  self.redraw_count = 0
  self._highlight_states = {}
  self._queries = {}

  -- Queries for a specific language can be overridden by a custom
  -- string query... if one is not provided it will be looked up by file.
  if opts.queries then
    for lang, query_string in pairs(opts.queries) do
      self._queries[lang] = TSHighlighterQuery.new(lang, query_string)
    end
  end

  self.orig_spelloptions = vim.bo[self.bufnr].spelloptions

  vim.bo[self.bufnr].syntax = ''
  vim.b[self.bufnr].ts_highlight = true

  TSHighlighter.active[self.bufnr] = self

  -- Tricky: if syntax hasn't been enabled, we need to reload color scheme
  -- but use synload.vim rather than syntax.vim to not enable
  -- syntax FileType autocmds. Later on we should integrate with the
  -- `:syntax` and `set syntax=...` machinery properly.
  if vim.g.syntax_on ~= 1 then
    vim.cmd.runtime({ 'syntax/synload.vim', bang = true })
  end

  api.nvim_buf_call(self.bufnr, function()
    vim.opt_local.spelloptions:append('noplainbuffer')
  end)

  self.tree:parse()

  return self
end

--- @nodoc
--- Removes all internal references to the highlighter
function TSHighlighter:destroy()
  TSHighlighter.active[self.bufnr] = nil

  if api.nvim_buf_is_loaded(self.bufnr) then
    vim.bo[self.bufnr].spelloptions = self.orig_spelloptions
    vim.b[self.bufnr].ts_highlight = nil
    if vim.g.syntax_on == 1 then
      api.nvim_exec_autocmds('FileType', { group = 'syntaxset', buffer = self.bufnr })
    end
  end
end

---@param srow integer
---@param erow integer exclusive
---@private
function TSHighlighter:prepare_highlight_states(srow, erow)
  self._highlight_states = {}

  self.tree:for_each_tree(function(tstree, tree)
    if not tstree then
      return
    end

    local root_node = tstree:root()
    local root_start_row, _, root_end_row, _ = root_node:range()

    -- Only consider trees within the visible range
    if root_start_row > erow or root_end_row < srow then
      return
    end

    local highlighter_query = self:get_query(tree:lang())

    -- Some injected languages may not have highlight queries.
    if not highlighter_query:query() then
      return
    end

    -- _highlight_states should be a list so that the highlights are added in the same order as
    -- for_each_tree traversal. This ensures that parents' highlight don't override children's.
    table.insert(self._highlight_states, {
      tstree = tstree,
      next_row = 0,
      iter = nil,
      highlighter_query = highlighter_query,
    })
  end)
end

---@param fn fun(state: vim.treesitter.highlighter.State)
---@package
function TSHighlighter:for_each_highlight_state(fn)
  for _, state in ipairs(self._highlight_states) do
    fn(state)
  end
end

---@package
---@param start_row integer
---@param new_end integer
function TSHighlighter:on_bytes(_, _, start_row, _, _, _, _, _, new_end)
  api.nvim__buf_redraw_range(self.bufnr, start_row, start_row + new_end + 1)
end

---@package
function TSHighlighter:on_detach()
  self:destroy()
end

---@package
---@param changes Range6[]
function TSHighlighter:on_changedtree(changes)
  for _, ch in ipairs(changes) do
    api.nvim__buf_redraw_range(self.bufnr, ch[1], ch[4] + 1)
  end
end

--- Gets the query used for @param lang
--
---@package
---@param lang string Language used by the highlighter.
---@return vim.treesitter.highlighter.Query
function TSHighlighter:get_query(lang)
  if not self._queries[lang] then
    self._queries[lang] = TSHighlighterQuery.new(lang)
  end

  return self._queries[lang]
end

---@param self vim.treesitter.highlighter
---@param buf integer
---@param line integer
---@param is_spell_nav boolean
local function on_line_impl(self, buf, line, is_spell_nav)
  self:for_each_highlight_state(function(state)
    local root_node = state.tstree:root()
    local root_start_row, _, root_end_row, _ = root_node:range()

    -- Only consider trees that contain this line
    if root_start_row > line or root_end_row < line then
      return
    end

    if state.iter == nil or state.next_row < line then
      state.iter =
        state.highlighter_query:query():iter_captures(root_node, self.bufnr, line, root_end_row + 1)
    end

    while line >= state.next_row do
      local capture, node, metadata = state.iter(line)

      local range = { root_end_row + 1, 0, root_end_row + 1, 0 }
      if node then
        range = vim.treesitter.get_range(node, buf, metadata and metadata[capture])
      end
      local start_row, start_col, end_row, end_col = Range.unpack4(range)

      if capture then
        local hl = state.highlighter_query:get_hl_from_capture(capture)

        local capture_name = state.highlighter_query:query().captures[capture]
        local spell = nil ---@type boolean?
        if capture_name == 'spell' then
          spell = true
        elseif capture_name == 'nospell' then
          spell = false
        end

        -- Give nospell a higher priority so it always overrides spell captures.
        local spell_pri_offset = capture_name == 'nospell' and 1 or 0

        if hl and end_row >= line and (not is_spell_nav or spell ~= nil) then
          local priority = (tonumber(metadata.priority) or vim.highlight.priorities.treesitter)
            + spell_pri_offset
          api.nvim_buf_set_extmark(buf, ns, start_row, start_col, {
            end_line = end_row,
            end_col = end_col,
            hl_group = hl,
            ephemeral = true,
            priority = priority,
            conceal = metadata.conceal,
            spell = spell,
          })
        end
      end

      if start_row > line then
        state.next_row = start_row
      end
    end
  end)
end

---@private
---@param _win integer
---@param buf integer
---@param line integer
function TSHighlighter._on_line(_, _win, buf, line, _)
  local self = TSHighlighter.active[buf]
  if not self then
    return
  end

  on_line_impl(self, buf, line, false)
end

---@private
---@param buf integer
---@param srow integer
---@param erow integer
function TSHighlighter._on_spell_nav(_, _, buf, srow, _, erow, _)
  local self = TSHighlighter.active[buf]
  if not self then
    return
  end

  self:prepare_highlight_states(srow, erow)

  for row = srow, erow do
    on_line_impl(self, buf, row, true)
  end
end

---@private
---@param _win integer
---@param buf integer
---@param topline integer
---@param botline integer
function TSHighlighter._on_win(_, _win, buf, topline, botline)
  local self = TSHighlighter.active[buf]
  if not self then
    return false
  end
  self.tree:parse({ topline, botline + 1 })
  self:prepare_highlight_states(topline, botline + 1)
  self.redraw_count = self.redraw_count + 1
  return true
end

api.nvim_set_decoration_provider(ns, {
  on_win = TSHighlighter._on_win,
  on_line = TSHighlighter._on_line,
  _on_spell_nav = TSHighlighter._on_spell_nav,
})

return TSHighlighter
