local api = vim.api

local locals = require'nvim-treesitter.locals'
local parsers = require'nvim-treesitter.parsers'

local M = {}

--- Gets the actual text content of a node
-- @param node the node to get the text from
-- @param bufnr the buffer containing the node
-- @return list of lines of text of the node
function M.get_node_text(node, bufnr)
  local bufnr = bufnr or api.nvim_get_current_buf()
  if not node then return {} end

  -- We have to remember that end_col is end-exclusive
  local start_row, start_col, end_row, end_col = node:range()

  if start_row ~= end_row then
    local lines = api.nvim_buf_get_lines(bufnr, start_row, end_row+1, false)
    lines[1] = string.sub(lines[1], start_col+1)
    lines[#lines] = string.sub(lines[#lines], 1, end_col)
    return lines
  else
    local line = api.nvim_buf_get_lines(bufnr, start_row, start_row+1, false)[1]
    -- If line is nil then the line is empty
    return line and { string.sub(line, start_col+1, end_col) } or {}
  end
end

--- Determines whether a node is the parent of another
-- @param dest the possible parent
-- @param source the possible child node
function M.is_parent(dest, source)
  if not (dest and source) then return false end

  local current = source
  while current ~= nil do
    if current == dest then
      return true
    end

    current = current:parent()
  end

  return false
end

--- Get next node with same parent
-- @param node                 node
-- @param allow_switch_parents allow switching parents if last node
-- @param allow_next_parent    allow next parent if last node and next parent without children
function M.get_next_node(node, allow_switch_parents, allow_next_parent)
  local destination_node
  local parent = node:parent()

  if not parent then return end
  local found_pos = 0
  for i = 0,parent:named_child_count()-1,1 do
    if parent:named_child(i) == node then
      found_pos = i
      break
    end
  end
  if parent:named_child_count() > found_pos + 1 then
    destination_node = parent:named_child(found_pos + 1)
  elseif allow_switch_parents then
    local next_node = M.get_next_node(node:parent())
    if next_node and next_node:named_child_count() > 0 then
      destination_node = next_node:named_child(0)
    elseif next_node and allow_next_parent then
      destination_node = next_node
    end
  end

  return destination_node
end

--- Get previous node with same parent
-- @param node                     node
-- @param allow_switch_parents     allow switching parents if first node
-- @param allow_previous_parent    allow previous parent if first node and previous parent without children
function M.get_previous_node(node, allow_switch_parents, allow_previous_parent)
  local destination_node
  local parent = node:parent()
  if not parent then return end

  local found_pos = 0
  for i = 0,parent:named_child_count()-1,1 do
    if parent:named_child(i) == node then
      found_pos = i
      break
    end
  end
  if 0 < found_pos then
    destination_node = parent:named_child(found_pos - 1)
  elseif allow_switch_parents then
    local previous_node = M.get_previous_node(node:parent())
    if previous_node and previous_node:named_child_count() > 0 then
      destination_node = previous_node:named_child(previous_node:named_child_count() - 1)
    elseif previous_node and allow_previous_parent then
      destination_node = previous_node
    end
  end
  return destination_node
end

function M.parent_scope(node, cursor_pos)
  local bufnr = api.nvim_get_current_buf()

  local scopes = locals.get_scopes(bufnr)
  if not node or not scopes then return end

  local row = cursor_pos.row
  local col = cursor_pos.col
  local iter_node = node

  while iter_node ~= nil do
    local row_, col_ = iter_node:start()
    if vim.tbl_contains(scopes, iter_node) and (row_+1 ~= row or col_ ~= col) then
      return iter_node
    end
    iter_node = iter_node:parent()
  end
end

function M.containing_scope(node, bufnr)
  local bufnr = bufnr or api.nvim_get_current_buf()

  local scopes = locals.get_scopes(bufnr)
  if not node or not scopes then return end

  local iter_node = node

  while iter_node ~= nil and not vim.tbl_contains(scopes, iter_node) do
    iter_node = iter_node:parent()
  end

  return iter_node or node
end

function M.get_named_children(node)
  local nodes = {}
  for i=0,node:named_child_count() - 1,1 do
    nodes[i+1] = node:named_child(i)
  end
  return nodes
end

function M.nested_scope(node, cursor_pos)
  local bufnr = api.nvim_get_current_buf()

  local scopes = locals.get_scopes(bufnr)
  if not node or not scopes then return end

  local row = cursor_pos.row
  local col = cursor_pos.col
  local scope = M.containing_scope(node)

  for _, child in ipairs(M.get_named_children(scope)) do
    local row_, col_ = child:start()
    if vim.tbl_contains(scopes, child) and ((row_+1 == row and col_ > col) or row_+1 > row) then
      return child
    end
  end
end

function M.next_scope(node)
  local bufnr = api.nvim_get_current_buf()

  local scopes = locals.get_scopes(bufnr)
  if not node or not scopes then return end

  local scope = M.containing_scope(node)

  local parent = scope:parent()
  if not parent then return end

  local is_prev = true
  for _, child in ipairs(M.get_named_children(parent)) do
    if child == scope then
      is_prev = false
    elseif not is_prev and vim.tbl_contains(scopes, child) then
      return child
    end
  end
end

function M.previous_scope(node)
  local bufnr = api.nvim_get_current_buf()

  local scopes = locals.get_scopes(bufnr)
  if not node or not scopes then return end

  local scope = M.containing_scope(node)

  local parent = scope:parent()
  if not parent then return end

  local is_prev = true
  local children = M.get_named_children(parent)
  for i=#children,1,-1 do
    if children[i] == scope then
      is_prev = false
    elseif not is_prev and vim.tbl_contains(scopes, children[i]) then
      return children[i]
    end
  end
end

function M.get_node_at_cursor(winnr)
  local cursor = api.nvim_win_get_cursor(winnr or 0)
  local root = parsers.get_parser().tree:root()
  return root:named_descendant_for_range(cursor[1]-1,cursor[2],cursor[1]-1,cursor[2])
end

-- Finds the definition node and it's scope node of a node
-- @param node starting node
-- @param bufnr buffer
-- @returns the definition node and the definition nodes scope node
function M.find_definition(node, bufnr)
  local bufnr = bufnr or api.nvim_get_current_buf()
  local node_text = M.get_node_text(node)[1]
  local current_scope = M.containing_scope(node)
  local matching_def_nodes = {}

  -- If a scope wasn't found then use the root node
  if current_scope == node then
    current_scope = parsers.get_parser(bufnr).tree:root()
  end

  -- Get all definitions that match the node text
  for _, def in ipairs(locals.get_definitions(bufnr)) do
    for _, def_node in ipairs(M.get_local_nodes(def)) do
      if M.get_node_text(def_node)[1] == node_text then
        table.insert(matching_def_nodes, def_node)
      end
    end
  end

  -- Continue up each scope until we find the scope that contains the definition
  while current_scope do
    for _, def_node in ipairs(matching_def_nodes) do
      if M.is_parent(current_scope, def_node) then
        return def_node, current_scope
      end
    end
    current_scope = M.containing_scope(current_scope:parent())
  end

  return node, parsers.get_parser(bufnr).tree:root()
end

-- Gets all nodes from a local list result.
-- @param local_def the local list result
-- @returns a list of nodes
function M.get_local_nodes(local_def)
  local result = {}

  M.recurse_local_nodes(local_def, function(_, node)
    table.insert(result, node)
  end)

  return result
end

-- Recurse locals results until a node is found.
-- The accumulator function is given
-- * The table of the node
-- * The node
-- * The full definition match `@definition.var.something` -> 'var.something'
-- * The last definition match `@definition.var.something` -> 'something'
-- @param The locals result
-- @param The accumulator function
-- @param The full match path to append to
-- @param The last match
function M.recurse_local_nodes(local_def, accumulator, full_match, last_match)
  if local_def.node then
    accumulator(local_def, local_def.node, full_match, last_match)
  else
    for match_key, def in pairs(local_def) do
      M.recurse_local_nodes(
        def,
        accumulator,
        full_match and (full_match..'.'..match_key) or match_key,
        match_key)
    end
  end
end

-- Finds usages of a node in a given scope
-- @param node the node to find usages for
-- @param scope_node the node to look within
-- @returns a list of nodes
function M.find_usages(node, scope_node, bufnr)
  local bufnr = bufnr or api.nvim_get_current_buf()
  local node_text = M.get_node_text(node)[1]

  if not node_text or #node_text < 1 then return {} end

  local scope_node = scope_node or parsers.get_parser(bufnr).tree:root()
  local usages = {}

  for match in locals.iter_locals(bufnr, scope_node) do
    if match.reference
      and match.reference.node
      and M.get_node_text(match.reference.node)[1] == node_text
    then
      table.insert(usages, match.reference.node)
    end
  end

  return usages
end

function M.highlight_node(node, buf, hl_namespace, hl_group)
  if not node then return end
  M.highlight_range({node:range()}, buf, hl_namespace, hl_group)
end

function M.highlight_range(range, buf, hl_namespace, hl_group)
  local start_row, start_col, end_row, end_col = unpack(range)
  vim.highlight.range(buf, hl_namespace, hl_group, {start_row, start_col}, {end_row, end_col})
end

-- Set visual selection to node
function M.update_selection(buf, node)
  local start_row, start_col, end_row, end_col
  if type(node) == 'table' then
    start_row, start_col, end_row, end_col = unpack(node)
  else
    start_row, start_col, end_row, end_col = node:range()
  end

  if end_row == vim.fn.line('$') then
    end_col = #vim.fn.getline('$')
  end

  -- Convert to 1-based indices
  start_row = start_row + 1
  start_col = start_col + 1
  end_row = end_row + 1
  end_col = end_col + 1

  vim.fn.setpos(".", { buf, start_row, start_col, 0 })
  vim.fn.nvim_exec("normal v", false)

  -- Convert exclusive end position to inclusive
  if end_col == 1 then
    vim.fn.setpos(".", { buf, end_row - 1, -1, 0 })
  else
    vim.fn.setpos(".", { buf, end_row, end_col - 1, 0 })
  end
end

-- Byte length of node range
function M.node_length(node)
  local _, _, start_byte = node:start()
  local _, _, end_byte = node:end_()
  return end_byte - start_byte
end

--- Determines whether (line, col) position is in node range
-- @param node Node defining the range
-- @param line A line (0-based)
-- @param col A column (0-based)
function M.is_in_node_range(node, line, col)
  local start_line, start_col, end_line, end_col = node:range()
  if line >= start_line and line <= end_line then
    if line == start_line and line == end_line then
      return col >= start_col and col < end_col
    elseif line == start_line then
      return col >= start_col
    elseif line == end_line then
      return col < end_col
    else
      return true
    end
  else
    return false
  end
end

return M