local M = {}

--- @class FffLayoutConfig
--- @field height number
--- @field width number
--- @field prompt_position string
--- @field preview_position string
--- @field preview_size number
--- @field min_list_height number
--- @field show_scrollbar boolean
--- @field path_shorten_strategy string
--- @field border? 'single'|'double'|'rounded'|'solid'|'shadow'|'none' Border preset; falls back to `vim.o.winborder` when nil

--- @class FffPreviewConfig
--- @field enabled boolean
--- @field max_size number
--- @field chunk_size number
--- @field binary_file_threshold number
--- @field imagemagick_info_format_str string
--- @field line_numbers boolean
--- @field cursorlineopt string
--- @field wrap_lines boolean
--- @field filetypes table<string, table>

--- @class FffKeymapsConfig
--- @field close string
--- @field select string
--- @field select_split string
--- @field select_vsplit string
--- @field select_tab string
--- @field move_up string|string[]
--- @field move_down string|string[]
--- @field preview_scroll_up string
--- @field preview_scroll_down string
--- @field toggle_debug string
--- @field cycle_grep_modes string
--- @field cycle_previous_query string
--- @field cycle_forward_query string
--- @field grep_jump_to_next_file string|string[]
--- @field grep_jump_to_prev_file string|string[]
--- @field toggle_select string
--- @field send_to_quickfix string
--- @field focus_list string
--- @field focus_preview string

--- @class FffFrecencyConfig
--- @field enabled boolean
--- @field db_path string

--- @class FffHistoryConfig
--- @field enabled boolean
--- @field db_path string
--- @field min_combo_count number
--- @field combo_boost_score_multiplier number

--- @class FffGrepConfig
--- @field max_file_size number
--- @field max_matches_per_file number
--- @field smart_case boolean
--- @field time_budget_ms number
--- @field modes string[]
--- @field trim_whitespace boolean
--- @field location_format string

--- @alias FffSelectAction 'edit' | 'split' | 'vsplit' | 'tab'

--- @class FffSelectConfig
--- @field select_window fun(current_buf: integer, action: FffSelectAction): integer|nil

--- @class FffConfig
--- @field base_path string
--- @field prompt string
--- @field title string
--- @field max_results number
--- @field max_threads number
--- @field lazy_sync boolean
--- @field prompt_vim_mode boolean
--- @field follow_symlinks boolean
--- @field enable_fs_root_scanning boolean
--- @field enable_home_dir_scanning boolean
--- @field layout FffLayoutConfig
--- @field preview FffPreviewConfig
--- @field keymaps FffKeymapsConfig
--- @field hl table<string, string>
--- @field frecency FffFrecencyConfig
--- @field history FffHistoryConfig
--- @field select FffSelectConfig
--- @field git table
--- @field debug table
--- @field logging table
--- @field wrap_around boolean
--- @field file_picker table
--- @field grep FffGrepConfig

---@class fff.conf.State
local state = {
  ---@type FffConfig|nil
  config = nil,
}

local DEPRECATION_RULES = {
  {
    -- Top-level width -> layout.width
    old_path = { 'width' },
    new_path = { 'layout', 'width' },
    message = 'config.width is deprecated. Use config.layout.width instead.',
  },
  {
    -- Top-level height -> layout.height
    old_path = { 'height' },
    new_path = { 'layout', 'height' },
    message = 'config.height is deprecated. Use config.layout.height instead.',
  },
  {
    -- preview.width -> layout.preview_size
    old_path = { 'preview', 'width' },
    new_path = { 'layout', 'preview_size' },
    message = 'config.preview.width is deprecated. Use config.layout.preview_size instead.',
  },
  {
    -- layout.preview_width -> layout.preview_size
    old_path = { 'layout', 'preview_width' },
    new_path = { 'layout', 'preview_size' },
    message = 'config.layout.preview_width is deprecated. Use config.layout.preview_size instead.',
  },
}

--- Get value from nested table using path array
--- @param tbl table Source table
--- @param path table Array of keys to traverse
--- @return any|nil Value at path or nil if not found
local function get_nested_value(tbl, path)
  local current = tbl
  for _, key in ipairs(path) do
    if type(current) ~= 'table' or current[key] == nil then return nil end
    current = current[key]
  end

  return current
end

--- Set value in nested table using path array, creating intermediate tables
--- @param tbl table Target table
--- @param path table Array of keys to traverse
--- @param value any Value to set
local function set_nested_value(tbl, path, value)
  local current = tbl
  for i = 1, #path - 1 do
    local key = path[i]
    if type(current[key]) ~= 'table' then current[key] = {} end
    current = current[key]
  end

  current[path[#path]] = value
end

--- Remove value from nested table using path array
--- @param tbl table Target table
--- @param path table Array of keys to traverse
local function remove_nested_value(tbl, path)
  if #path == 0 then return end

  local current = tbl
  for i = 1, #path - 1 do
    local key = path[i]
    if type(current[key]) ~= 'table' then return end
    current = current[key]
  end

  current[path[#path]] = nil
end

--- Handle deprecated configuration options with migration warnings
--- @param user_config table User provided configuration
--- @return table Migrated configuration
local function handle_deprecated_config(user_config)
  if not user_config then return {} end

  local migrated_config = vim.deepcopy(user_config)

  for _, rule in ipairs(DEPRECATION_RULES) do
    local old_value = get_nested_value(user_config, rule.old_path)
    if old_value ~= nil then
      set_nested_value(migrated_config, rule.new_path, old_value)
      remove_nested_value(migrated_config, rule.old_path)

      vim.notify('FFF: ' .. rule.message, vim.log.levels.WARN)
    end
  end

  return migrated_config
end

---@param name table list of highlight groups to choose from
---@return string one of the provided groups
local function fallback_hl(name)
  local resolved_hl
  for _, hl in ipairs(name) do
    local resolved_group = vim.api.nvim_get_hl(0, { name = hl })

    if not vim.tbl_isempty(resolved_group) then resolved_hl = hl end
  end

  return resolved_hl or name[#name]
end

local function init()
  local config = vim.g.fff or {}
  local default_config = {
    base_path = vim.fn.getcwd(),
    prompt = '🪿 ',
    title = 'FFFiles',
    max_results = 100,
    max_threads = 4,
    lazy_sync = true, -- set to false if you want file indexing to start on open
    prompt_vim_mode = false, -- set to true to enable vim-mode in the prompt: <Esc> leaves insert for normal mode bindings (also allows <leader>p or <leader>l to jump around) the second <Esc> closes the picker
    wrap_around = false, -- set to true to wrap cursor to the opposite end when reaching the first/last item
    follow_symlinks = false, -- set to true to follow symbolic links during file indexing
    -- Allow fff in the user's $HOME director.
    enable_home_dir_scanning = true,
    -- Allow fff in a filesystem root (e.g. `/`, `C:\`)
    enable_fs_root_scanning = false,
    layout = {
      height = 0.8,
      width = 0.8,
      prompt_position = 'bottom', -- or 'top'
      preview_position = 'right', -- or 'left', 'right', 'top', 'bottom'
      preview_size = 0.5,
      -- Border style for the picker windows: 'single', 'double', 'rounded',
      -- 'solid', 'shadow' or 'none'. Leave unset (nil) to follow the global
      -- `vim.o.winborder` setting.
      border = nil,
      flex = { -- set to nil to disable flex layout
        size = 130, -- column threshold: if screen width >= size, use preview_position; otherwise use wrap
        wrap = 'top', -- position to use when screen is narrower than size
      },
      -- Minimum list height required to render the preview. When the available
      -- list area would drop below this on small terminals, the preview is
      -- auto-hidden so the file list stays usable. Set to 0 to disable.
      min_list_height = 10,
      show_scrollbar = true, -- Show scrollbar for pagination
      -- How to shorten long directory paths in the file list:
      -- 'middle' (default): always uses dots (a/./b, a/../b, a/.../b)
      -- 'middle_number' uses dots for 1-3 hidden (a/./b, a/../b, a/.../b)
      --                 and numbers for 4+ (a/.4./b, a/.5./b)
      -- 'end': truncates from the end, keeps the start (home/user/projects)
      -- 'start': truncates from the start, keeps the end (.../parts/ai_extracted)
      path_shorten_strategy = 'middle',
    },
    preview = {
      enabled = true,
      max_size = 10 * 1024 * 1024, -- Do not try to read files larger than 10MB
      chunk_size = 8192, -- Bytes per chunk for dynamic loading (8kb - fits ~100-200 lines)
      binary_file_threshold = 1024, -- amount of bytes to scan for binary content (set 0 to disable)
      imagemagick_info_format_str = '%m: %wx%h, %[colorspace], %q-bit',
      line_numbers = false,
      cursorlineopt = 'both',
      wrap_lines = false,
      filetypes = {
        svg = { wrap_lines = true },
        markdown = { wrap_lines = true },
        text = { wrap_lines = true },
      },
    },
    keymaps = {
      close = '<Esc>',
      select = '<CR>',
      select_split = '<C-s>',
      select_vsplit = '<C-v>',
      select_tab = '<C-t>',
      -- you can assign multiple keys to any action
      move_up = { '<Up>', '<C-p>' },
      move_down = { '<Down>', '<C-n>' },
      preview_scroll_up = '<C-u>',
      preview_scroll_down = '<C-d>',
      toggle_debug = '<F2>',
      -- grep mode: cycle between plain text, regex, and fuzzy search
      cycle_grep_modes = '<S-Tab>',
      -- grep mode only: jump cursor to first item of next/prev file group
      grep_jump_to_next_file = { '<C-A-n>', '<A-Down>' },
      grep_jump_to_prev_file = { '<C-A-p>', '<A-Up>' },
      -- goes to the previous query in history
      cycle_previous_query = '<C-Up>',
      -- goes to the next query in history (forward)
      cycle_forward_query = '<C-Down>',
      -- multi-select keymaps for quickfix
      toggle_select = '<Tab>',
      send_to_quickfix = '<C-q>',
      -- this are specific for the normal mode (you can exit it using any other keybind like jj)
      focus_list = '<leader>l',
      focus_preview = '<leader>p',
    },
    hl = {
      border = 'FloatBorder',
      normal = 'NormalFloat',
      matched = 'IncSearch',
      title = 'Title',
      prompt = 'Question',
      cursor = fallback_hl({ 'CursorLine', 'Visual' }),
      frecency = 'Number',
      debug = 'Comment',
      combo_header = 'Number',
      scrollbar = 'Comment',
      directory_path = 'Comment',
      -- Multi-select highlights
      selected = 'FFFSelected',
      selected_active = 'FFFSelectedActive',
      -- Git text highlights for file names
      git_staged = 'FFFGitStaged',
      git_modified = 'FFFGitModified',
      git_deleted = 'FFFGitDeleted',
      git_renamed = 'FFFGitRenamed',
      git_untracked = 'FFFGitUntracked',
      git_ignored = 'FFFGitIgnored',
      -- Git sign/border highlights
      git_sign_staged = 'FFFGitSignStaged',
      git_sign_modified = 'FFFGitSignModified',
      git_sign_deleted = 'FFFGitSignDeleted',
      git_sign_renamed = 'FFFGitSignRenamed',
      git_sign_untracked = 'FFFGitSignUntracked',
      git_sign_ignored = 'FFFGitSignIgnored',
      -- Git sign selected highlights
      git_sign_staged_selected = 'FFFGitSignStagedSelected',
      git_sign_modified_selected = 'FFFGitSignModifiedSelected',
      git_sign_deleted_selected = 'FFFGitSignDeletedSelected',
      git_sign_renamed_selected = 'FFFGitSignRenamedSelected',
      git_sign_untracked_selected = 'FFFGitSignUntrackedSelected',
      git_sign_ignored_selected = 'FFFGitSignIgnoredSelected',
      -- Grep highlights
      grep_match = 'IncSearch', -- Highlight for matched text in grep results
      grep_line_number = 'LineNr', -- Highlight for :line:col location
      grep_regex_active = 'DiagnosticInfo', -- Highlight for keybind + label when regex is on
      grep_plain_active = 'Comment', -- Highlight for keybind + label when regex is off
      grep_fuzzy_active = 'DiagnosticHint', -- Highlight for keybind + label when fuzzy is on
      -- Cross-mode suggestion highlights
      suggestion_header = 'WarningMsg', -- Highlight for the "No results found. Suggested..." banner
      -- File info panel highlights
      file_info_section = 'FFFFileInfoSection', -- Section header label (e.g. "file", "score")
      file_info_separator = 'FFFFileInfoSeparator', -- Dash dividers used like a border
      file_info_label = 'FFFFileInfoLabel', -- Row labels (Size, Type, Git, ...)
      file_info_value = 'FFFFileInfoValue', -- Plain values
      file_info_value_dim = 'FFFFileInfoValueDim', -- Tertiary values, separators inside rows
      file_info_size = 'FFFFileInfoSize', -- File size value
      file_info_type = 'FFFFileInfoType', -- Filetype value
      file_info_path = 'FFFFileInfoPath', -- Full path value
      file_info_total_score = 'FFFFileInfoTotalScore', -- Total score (bold)
      file_info_match_type = 'FFFFileInfoMatchType', -- match_type label (bold)
      file_info_score_pos = 'FFFFileInfoScorePos', -- Positive score components
      file_info_score_neg = 'FFFFileInfoScoreNeg', -- Negative score components / penalties
      -- Per-window 'winhighlight' overrides. When nil, falls back to a combination of `normal`, `border`, and `title` above.
      -- Accepts either a string applied to every picker window, or a table with optional `prompt`, `list`, `preview`, `file_info` keys.
      -- Example: `winhl = 'Normal:NormalFloat,FloatBorder:FloatBorder,FloatTitle:Title'`
      -- Example: `winhl = { prompt = 'Normal:Pmenu,...', list = 'Normal:NormalFloat,...' }`
      winhl = nil,
    },
    -- Store file open frecency
    frecency = {
      enabled = true,
      db_path = vim.fn.stdpath('cache') .. '/fff_nvim',
    },
    -- Store successfully opened queries with respective matches
    history = {
      enabled = true,
      db_path = vim.fn.stdpath('data') .. '/fff_queries',
      min_combo_count = 3, -- Minimum selections before combo boost applies (3 = boost starts on 3rd selection)
      combo_boost_score_multiplier = 100, -- Score multiplier for combo matches (files repeatedly opened with same query)
    },
    select = {
      --- Returns winid to open the file in. Return nil to open in the invoking
      --- window. Default retargets when the invoking window can't host a file
      --- buffer (special buftype, non-modifiable, or winfixbuf).
      --- @param current_buf integer
      --- @param action FffSelectAction
      --- @return integer|nil
      select_window = function(current_buf, action)
        if action ~= 'edit' then return nil end
        local current_win = vim.api.nvim_get_current_win()
        local buftype = vim.api.nvim_get_option_value('buftype', { buf = current_buf })
        local modifiable = vim.api.nvim_get_option_value('modifiable', { buf = current_buf })
        local winfixbuf = require('fff.utils').window_has_winfixbuf(current_win)
        if buftype == '' and modifiable and not winfixbuf then return nil end
        return require('fff.utils').find_suitable_window()
      end,
    },
    -- Git integration
    git = {
      status_text_color = false, -- Apply git status colors to filename text (default: false, only sign column)
    },
    debug = {
      enabled = false, -- Show file info panel in preview
      show_scores = false, -- Show scores inline in the UI
      show_file_info = {
        file_info = true, -- Size, type, git status, frecency
        score_breakdown = true, -- Total + match type, bonuses, modifiers, penalty
        -- Modified + accessed timestamps. Pass a boolean to toggle the
        -- whole section, or a table to hide individual rows:
        --   timings = { modified = false, accessed = true }
        timings = true,
        full_path = true, -- Full absolute path at the bottom
      },
    },
    logging = {
      enabled = true,
      -- Path-shape hint: each nvim startup writes a fresh sibling file
      -- `<stem>+<UTC-timestamp>+<pid>.<ext>` next to this path. The literal
      -- path itself is never written to — multiple concurrent nvim instances
      -- get their own per-pid file with no locking.
      log_file = vim.fn.stdpath('log') .. '/fff.log',
      log_level = 'info',
      -- How many session log files to retain. Newest are kept, older are
      -- pruned on the next startup. Set to 0 to disable retention.
      retain_runs = 20,
    },
    -- find_files settings
    file_picker = {
      current_file_label = '(current)',
    },
    -- grep settings
    grep = {
      max_file_size = 10 * 1024 * 1024, -- Skip files larger than 10MB
      max_matches_per_file = 100, -- Maximum matches per file (set 0 to unlimited)
      smart_case = true, -- Case-insensitive unless query has uppercase
      time_budget_ms = 150, -- Max search time in ms per call (prevents UI freeze, 0 = no limit)
      modes = { 'plain', 'regex', 'fuzzy' }, -- Available grep modes and their cycling order
      trim_whitespace = false, -- Strip leading whitespace from matched lines (useful for cleaner display)
      -- Treat filename-like tokens (e.g. `score.rs`, `src/main.rs`) in a grep query as a
      -- file-path filter, scoping the content search to matching files. When off, such
      -- tokens are searched as literal text. A token is a filename if it has a valid-looking
      -- extension and no wildcards.
      enable_filename_constraint = false,
      -- Format string for the line/column location prefix in grep results.
      -- Uses vim's printf-style format: %d placeholders for line and column (1-based).
      -- Default ':%d:%d' renders as ':356:1'. Use ':%d' for line-only ':356'.
      location_format = ':%d:%d',
    },
  }

  local migrated_user_config = handle_deprecated_config(config)
  local merged_config = vim.tbl_deep_extend('force', default_config, migrated_user_config)

  -- Normalise show_file_info: accept a boolean shorthand or a partial table
  local sfi = merged_config.debug and merged_config.debug.show_file_info
  local default_sections = { file_info = true, score_breakdown = true, timings = true, full_path = true }
  if type(sfi) == 'boolean' then
    merged_config.debug.show_file_info = {
      file_info = sfi,
      score_breakdown = sfi,
      timings = sfi,
      full_path = sfi,
    }
  elseif type(sfi) == 'table' then
    for k, v in pairs(default_sections) do
      if sfi[k] == nil then sfi[k] = v end
    end
  else
    merged_config.debug.show_file_info = default_sections
  end

  state.config = merged_config
end

--- Setup the file picker with the given configuration
--- @param config FffConfig Configuration options
function M.setup(config) vim.g.fff = config end

--- @return FffConfig the fff configuration
function M.get()
  if not state.config then init() end
  return state.config
end

--- True when preview rendering is requested by config. Defaults to `true`
--- when `config` (or its `preview` block) is missing so callers don't have
--- to guard against partial state during init.
--- @param config? FffConfig Optional config; falls back to `M.get()` when nil.
--- @return boolean
function M.preview_enabled(config)
  config = config or M.get()
  if not config or not config.preview then return true end
  return config.preview.enabled
end

--- @return boolean state_changed
function M.toggle_debug()
  local old_debug_state = state.config.debug.show_scores
  state.config.debug.show_scores = not state.config.debug.show_scores
  state.config.debug.enabled = state.config.debug.show_scores
  local status = state.config.debug.show_scores and 'enabled' or 'disabled'
  vim.notify('FFF debug scores ' .. status, vim.log.levels.INFO)
  return old_debug_state ~= state.config.debug.show_scores
end

return M