local cache = require("oil.cache")
local columns = require("oil.columns")
local config = require("oil.config")
local constants = require("oil.constants")
local oil = require("oil")
local parser = require("oil.mutator.parser")
local pathutil = require("oil.pathutil")
local preview = require("oil.mutator.preview")
local Progress = require("oil.mutator.progress")
local Trie = require("oil.mutator.trie")
local util = require("oil.util")
local view = require("oil.view")
local M = {}

local FIELD_NAME = constants.FIELD_NAME
local FIELD_TYPE = constants.FIELD_TYPE

---@alias oil.Action oil.CreateAction|oil.DeleteAction|oil.MoveAction|oil.CopyAction|oil.ChangeAction

---@class (exact) oil.CreateAction
---@field type "create"
---@field url string
---@field entry_type oil.EntryType
---@field link nil|string

---@class (exact) oil.DeleteAction
---@field type "delete"
---@field url string
---@field entry_type oil.EntryType

---@class (exact) oil.MoveAction
---@field type "move"
---@field entry_type oil.EntryType
---@field src_url string
---@field dest_url string

---@class (exact) oil.CopyAction
---@field type "copy"
---@field entry_type oil.EntryType
---@field src_url string
---@field dest_url string

---@class (exact) oil.ChangeAction
---@field type "change"
---@field entry_type oil.EntryType
---@field url string
---@field column string
---@field value any

---@param all_diffs table<integer, oil.Diff[]>
---@return oil.Action[]
M.create_actions_from_diffs = function(all_diffs)
  ---@type oil.Action[]
  local actions = {}

  local diff_by_id = setmetatable({}, {
    __index = function(t, key)
      local list = {}
      rawset(t, key, list)
      return list
    end,
  })
  for bufnr, diffs in pairs(all_diffs) do
    local adapter = util.get_adapter(bufnr)
    if not adapter then
      error("Missing adapter")
    end
    local parent_url = vim.api.nvim_buf_get_name(bufnr)
    for _, diff in ipairs(diffs) do
      if diff.type == "new" then
        if diff.id then
          local by_id = diff_by_id[diff.id]
          -- FIXME this is kind of a hack. We shouldn't be setting undocumented fields on the diff
          ---@diagnostic disable-next-line: inject-field
          diff.dest = parent_url .. diff.name
          table.insert(by_id, diff)
        else
          -- Parse nested files like foo/bar/baz
          local pieces = vim.split(diff.name, "/")
          local url = parent_url:gsub("/$", "")
          for i, v in ipairs(pieces) do
            local is_last = i == #pieces
            local entry_type = is_last and diff.entry_type or "directory"
            local alternation = v:match("{([^}]+)}")
            if is_last and alternation then
              -- Parse alternations like foo.{js,test.js}
              for _, alt in ipairs(vim.split(alternation, ",")) do
                local alt_url = url .. "/" .. v:gsub("{[^}]+}", alt)
                table.insert(actions, {
                  type = "create",
                  url = alt_url,
                  entry_type = entry_type,
                  link = diff.link,
                })
              end
            else
              url = url .. "/" .. v
              table.insert(actions, {
                type = "create",
                url = url,
                entry_type = entry_type,
                link = diff.link,
              })
            end
          end
        end
      elseif diff.type == "change" then
        table.insert(actions, {
          type = "change",
          url = parent_url .. diff.name,
          entry_type = diff.entry_type,
          column = diff.column,
          value = diff.value,
        })
      else
        local by_id = diff_by_id[diff.id]
        by_id.has_delete = true
        -- Don't insert the delete. We already know that there is a delete because of the presense
        -- in the diff_by_id map. The list will only include the 'new' diffs.
      end
    end
  end

  for id, diffs in pairs(diff_by_id) do
    local entry = cache.get_entry_by_id(id)
    if not entry then
      error(string.format("Could not find entry %d", id))
    end
    if diffs.has_delete then
      local has_create = #diffs > 0
      if has_create then
        -- MOVE (+ optional copies) when has both creates and delete
        for i, diff in ipairs(diffs) do
          table.insert(actions, {
            type = i == #diffs and "move" or "copy",
            entry_type = entry[FIELD_TYPE],
            dest_url = diff.dest,
            src_url = cache.get_parent_url(id) .. entry[FIELD_NAME],
          })
        end
      else
        -- DELETE when no create
        table.insert(actions, {
          type = "delete",
          entry_type = entry[FIELD_TYPE],
          url = cache.get_parent_url(id) .. entry[FIELD_NAME],
        })
      end
    else
      -- COPY when create but no delete
      for _, diff in ipairs(diffs) do
        table.insert(actions, {
          type = "copy",
          entry_type = entry[FIELD_TYPE],
          src_url = cache.get_parent_url(id) .. entry[FIELD_NAME],
          dest_url = diff.dest,
        })
      end
    end
  end

  return M.enforce_action_order(actions)
end

---@param actions oil.Action[]
---@return oil.Action[]
M.enforce_action_order = function(actions)
  local src_trie = Trie.new()
  local dest_trie = Trie.new()
  for _, action in ipairs(actions) do
    if action.type == "delete" or action.type == "change" then
      src_trie:insert_action(action.url, action)
    elseif action.type == "create" then
      dest_trie:insert_action(action.url, action)
    else
      dest_trie:insert_action(action.dest_url, action)
      src_trie:insert_action(action.src_url, action)
    end
  end

  -- 1. create a graph, each node points to all of its dependencies
  -- 2. for each action, if not added, find it in the graph
  -- 3. traverse through the graph until you reach a node that has no dependencies (leaf)
  -- 4. append that action to the return value, and remove it from the graph
  --   a. TODO optimization: check immediate parents to see if they have no dependencies now
  -- 5. repeat

  ---Gets the dependencies of a particular action. Effectively dynamically calculates the dependency
  ---"edges" of the graph.
  ---@param action oil.Action
  local function get_deps(action)
    local ret = {}
    if action.type == "delete" then
      src_trie:accum_children_of(action.url, ret)
    elseif action.type == "create" then
      -- Finish operating on parents first
      -- e.g. NEW /a BEFORE NEW /a/b
      dest_trie:accum_first_parents_of(action.url, ret)
      -- Process remove path before creating new path
      -- e.g. DELETE /a BEFORE NEW /a
      src_trie:accum_actions_at(action.url, ret, function(a)
        return a.type == "move" or a.type == "delete"
      end)
    elseif action.type == "change" then
      -- Finish operating on parents first
      -- e.g. NEW /a BEFORE CHANGE /a/b
      dest_trie:accum_first_parents_of(action.url, ret)
      -- Finish operations on this path first
      -- e.g. NEW /a BEFORE CHANGE /a
      dest_trie:accum_actions_at(action.url, ret)
      -- Finish copy from operations first
      -- e.g. COPY /a -> /b BEFORE CHANGE /a
      src_trie:accum_actions_at(action.url, ret, function(entry)
        return entry.type == "copy"
      end)
    elseif action.type == "move" then
      -- Finish operating on parents first
      -- e.g. NEW /a BEFORE MOVE /z -> /a/b
      dest_trie:accum_first_parents_of(action.dest_url, ret)
      -- Process children before moving
      -- e.g. NEW /a/b BEFORE MOVE /a -> /b
      dest_trie:accum_children_of(action.src_url, ret)
      -- Copy children before moving parent dir
      -- e.g. COPY /a/b -> /b BEFORE MOVE /a -> /d
      src_trie:accum_children_of(action.src_url, ret, function(a)
        return a.type == "copy"
      end)
      -- Process remove path before moving to new path
      -- e.g. MOVE /a -> /b BEFORE MOVE /c -> /a
      src_trie:accum_actions_at(action.dest_url, ret, function(a)
        return a.type == "move" or a.type == "delete"
      end)
    elseif action.type == "copy" then
      -- Finish operating on parents first
      -- e.g. NEW /a BEFORE COPY /z -> /a/b
      dest_trie:accum_first_parents_of(action.dest_url, ret)
      -- Process children before copying
      -- e.g. NEW /a/b BEFORE COPY /a -> /b
      dest_trie:accum_children_of(action.src_url, ret)
      -- Process remove path before copying to new path
      -- e.g. MOVE /a -> /b BEFORE COPY /c -> /a
      src_trie:accum_actions_at(action.dest_url, ret, function(a)
        return a.type == "move" or a.type == "delete"
      end)
    end
    return ret
  end

  ---@return nil|oil.Action The leaf action
  ---@return nil|oil.Action When no leaves found, this is the last action in the loop
  local function find_leaf(action, seen)
    if not seen then
      seen = {}
    elseif seen[action] then
      return nil, action
    end
    seen[action] = true
    local deps = get_deps(action)
    if vim.tbl_isempty(deps) then
      return action
    end
    local action_in_loop
    for _, dep in ipairs(deps) do
      local leaf, loop_action = find_leaf(dep, seen)
      if leaf then
        return leaf
      elseif not action_in_loop and loop_action then
        action_in_loop = loop_action
      end
    end
    return nil, action_in_loop
  end

  local ret = {}
  local after = {}
  while not vim.tbl_isempty(actions) do
    local action = actions[1]
    local selected, loop_action = find_leaf(action)
    local to_remove
    if selected then
      to_remove = selected
    else
      if loop_action and loop_action.type == "move" then
        -- If this is moving a parent into itself, that's an error
        if vim.startswith(loop_action.dest_url, loop_action.src_url) then
          error("Detected cycle in desired paths")
        end

        -- We've detected a move cycle (e.g. MOVE /a -> /b + MOVE /b -> /a)
        -- Split one of the moves and retry
        local intermediate_url =
          string.format("%s__oil_tmp_%05d", loop_action.src_url, math.random(999999))
        local move_1 = {
          type = "move",
          entry_type = loop_action.entry_type,
          src_url = loop_action.src_url,
          dest_url = intermediate_url,
        }
        local move_2 = {
          type = "move",
          entry_type = loop_action.entry_type,
          src_url = intermediate_url,
          dest_url = loop_action.dest_url,
        }
        to_remove = loop_action
        table.insert(actions, move_1)
        table.insert(after, move_2)
        dest_trie:insert_action(move_1.dest_url, move_1)
        src_trie:insert_action(move_1.src_url, move_1)
      else
        error("Detected cycle in desired paths")
      end
    end

    if selected then
      if selected.type == "move" or selected.type == "copy" then
        if vim.startswith(selected.dest_url, selected.src_url .. "/") then
          error(
            string.format(
              "Cannot move or copy parent into itself: %s -> %s",
              selected.src_url,
              selected.dest_url
            )
          )
        end
      end
      table.insert(ret, selected)
    end

    if to_remove then
      if to_remove.type == "delete" or to_remove.type == "change" then
        src_trie:remove_action(to_remove.url, to_remove)
      elseif to_remove.type == "create" then
        dest_trie:remove_action(to_remove.url, to_remove)
      else
        dest_trie:remove_action(to_remove.dest_url, to_remove)
        src_trie:remove_action(to_remove.src_url, to_remove)
      end
      for i, a in ipairs(actions) do
        if a == to_remove then
          table.remove(actions, i)
          break
        end
      end
    end
  end

  vim.list_extend(ret, after)
  return ret
end

---@param actions oil.Action[]
---@param cb fun(err: nil|string)
M.process_actions = function(actions, cb)
  -- convert delete actions to move-to-trash
  local trash_url = config.get_trash_url()
  if trash_url then
    for i, v in ipairs(actions) do
      if v.type == "delete" then
        local scheme, path = util.parse_url(v.url)
        if config.adapters[scheme] == "files" then
          assert(path)
          ---@type oil.MoveAction
          local move_action = {
            type = "move",
            src_url = v.url,
            entry_type = v.entry_type,
            dest_url = trash_url .. "/" .. pathutil.basename(path) .. string.format(
              "_%06d",
              math.random(999999)
            ),
          }
          actions[i] = move_action
        end
      end
    end
  end

  -- Convert cross-adapter moves to a copy + delete
  for _, action in ipairs(actions) do
    if action.type == "move" then
      local src_scheme = util.parse_url(action.src_url)
      local dest_scheme = util.parse_url(action.dest_url)
      if src_scheme ~= dest_scheme then
        action.type = "copy"
        table.insert(actions, {
          type = "delete",
          url = action.src_url,
          entry_type = action.entry_type,
        })
      end
    end
  end

  local finished = false
  local progress = Progress.new()
  local function finish(...)
    if not finished then
      finished = true
      progress:close()
      cb(...)
    end
  end

  -- Defer showing the progress to avoid flicker for fast operations
  vim.defer_fn(function()
    if not finished then
      progress:show({
        -- TODO some actions are actually cancelable.
        -- We should stop them instead of stopping after the current action
        cancel = function()
          finish("Canceled")
        end,
      })
    end
  end, 100)

  local idx = 1
  local next_action
  next_action = function()
    if finished then
      return
    end
    if idx > #actions then
      finish()
      return
    end
    local action = actions[idx]
    progress:set_action(action, idx, #actions)
    idx = idx + 1
    local ok, adapter = pcall(util.get_adapter_for_action, action)
    if not ok then
      return finish(adapter)
    end
    local callback = vim.schedule_wrap(function(err)
      if finished then
        -- This can happen if the user canceled out of the progress window
        return
      elseif err then
        finish(err)
      else
        cache.perform_action(action)
        next_action()
      end
    end)
    if action.type == "change" then
      ---@cast action oil.ChangeAction
      columns.perform_change_action(adapter, action, callback)
    else
      adapter.perform_action(action, callback)
    end
  end
  next_action()
end

local mutation_in_progress = false

---@param confirm nil|boolean
M.try_write_changes = function(confirm)
  if mutation_in_progress then
    error("Cannot perform mutation when already in progress")
    return
  end
  local current_buf = vim.api.nvim_get_current_buf()
  local was_modified = vim.bo.modified
  local buffers = view.get_all_buffers()
  local all_diffs = {}
  local all_errors = {}

  mutation_in_progress = true
  -- Lock the buffer to prevent race conditions from the user modifying them during parsing
  view.lock_buffers()
  for _, bufnr in ipairs(buffers) do
    if vim.bo[bufnr].modified then
      local diffs, errors = parser.parse(bufnr)
      all_diffs[bufnr] = diffs
      if not vim.tbl_isempty(errors) then
        all_errors[bufnr] = errors
      end
    end
  end
  local function unlock()
    view.unlock_buffers()
    -- The ":write" will set nomodified even if we cancel here, so we need to restore it
    if was_modified then
      vim.bo[current_buf].modified = true
    end
    mutation_in_progress = false
  end

  local ns = vim.api.nvim_create_namespace("Oil")
  vim.diagnostic.reset(ns)
  if not vim.tbl_isempty(all_errors) then
    vim.notify("Error parsing oil buffers", vim.log.levels.ERROR)
    for bufnr, errors in pairs(all_errors) do
      vim.diagnostic.set(ns, bufnr, errors)
    end

    -- Jump to an error
    local curbuf = vim.api.nvim_get_current_buf()
    if all_errors[curbuf] then
      pcall(
        vim.api.nvim_win_set_cursor,
        0,
        { all_errors[curbuf][1].lnum + 1, all_errors[curbuf][1].col }
      )
    else
      ---@diagnostic disable-next-line: param-type-mismatch
      local bufnr, errs = next(pairs(all_errors))
      vim.api.nvim_win_set_buf(0, bufnr)
      pcall(vim.api.nvim_win_set_cursor, 0, { errs[1].lnum + 1, errs[1].col })
    end
    return unlock()
  end

  local actions = M.create_actions_from_diffs(all_diffs)
  preview.show(actions, confirm, function(proceed)
    if not proceed then
      return unlock()
    end

    M.process_actions(
      actions,
      vim.schedule_wrap(function(err)
        view.unlock_buffers()
        if err then
          vim.notify(string.format("[oil] Error applying actions: %s", err), vim.log.levels.ERROR)
          view.rerender_all_oil_buffers({ preserve_undo = false })
        else
          local current_entry = oil.get_cursor_entry()
          if current_entry then
            -- get the entry under the cursor and make sure the cursor stays on it
            view.set_last_cursor(
              vim.api.nvim_buf_get_name(0),
              vim.split(current_entry.parsed_name or current_entry.name, "/")[1]
            )
          end
          view.rerender_all_oil_buffers({ preserve_undo = M.trash })
        end
        mutation_in_progress = false
      end)
    )
  end)
end

return M