local case_policy = require("clever_f.case_policy")
local domain = require("clever_f.domain")
local text_topology = require("clever_f.text_topology")

local M = {}
local DirectPreviewPlanner = {}
DirectPreviewPlanner.__index = DirectPreviewPlanner
M.DirectPreviewPlanner = DirectPreviewPlanner

local planner_records = setmetatable({}, { __mode = "k" })

local function fail(message, level)
  error(message, (level or 1) + 1)
end

local function require_view(view)
  if not text_topology.TextView.is(view) then
    fail("direct preview text must be a TextView", 3)
  end
  return view
end

local function require_case_resolver(options)
  options = options or {}
  if type(options) == "function" then
    options = { lowercase = options }
  end
  if type(options) ~= "table" then
    fail("DirectPreviewPlanner options must be a table", 3)
  end
  local resolver = options.case_resolver
  if resolver == nil then
    resolver = case_policy.new({ lowercase = options.lowercase })
  end
  if type(resolver) ~= "table" or type(resolver.lowercase) ~= "function" then
    fail("DirectPreviewPlanner case resolver must provide lowercase", 3)
  end
  return resolver
end

function DirectPreviewPlanner.new(options)
  if DirectPreviewPlanner.is(options) then
    return options
  end
  local planner = setmetatable({}, DirectPreviewPlanner)
  planner_records[planner] = {
    case_resolver = require_case_resolver(options),
  }
  return planner
end

function DirectPreviewPlanner.is(value)
  return type(value) == "table" and planner_records[value] ~= nil
end

function DirectPreviewPlanner:scan_current_line(view, origin, direction)
  require_view(view)
  origin = domain.Position.coerce(origin)
  direction = domain.Direction.from_string(direction)
  local records = {}
  for position, character, span in view:iter_strict(
    origin,
    direction,
    domain.SearchScope.CURRENT_LINE
  ) do
    records[#records + 1] = {
      position = position,
      character = character,
      span = span,
    }
  end
  return records
end

function M.normalize_count(count)
  return domain.Count.to_number(count)
end

function DirectPreviewPlanner:normalize_count(count)
  return M.normalize_count(count)
end

function M.direction_for_descriptor(descriptor)
  descriptor = domain.Descriptor.from_string(descriptor)
  if domain.Descriptor.is_uppercase(descriptor) then
    return domain.Direction.BACKWARD
  end
  return domain.Direction.FORWARD
end

function DirectPreviewPlanner:scan_for_descriptor(view, origin, descriptor)
  return self:scan_current_line(
    view,
    origin,
    M.direction_for_descriptor(descriptor)
  )
end

local function increment_counter(counters, character)
  local value = (counters[character] or 0) + 1
  counters[character] = value
  return value
end

local function is_upper_ascii(character)
  if type(character) ~= "string" or #character ~= 1 then
    return false
  end
  local code = character:byte(1)
  return code >= string.byte("A") and code <= string.byte("Z")
end

local function increment_smart_counters(counters, character)
  local exact_count = increment_counter(counters, character)
  local lowercase_count
  if is_upper_ascii(character) then
    local lowercase = string.char(character:byte(1) + 32)
    lowercase_count = increment_counter(counters, lowercase)
  end
  return exact_count, lowercase_count
end

M.is_upper_ascii = is_upper_ascii

local function require_case_setting(settings, name)
  local value = settings[name]
  if value == nil then
    return false
  end
  if type(value) ~= "boolean" then
    fail("direct preview " .. name .. " must be a Boolean", 3)
  end
  return value
end

function DirectPreviewPlanner:plan(view, origin, descriptor, count, settings)
  settings = settings or {}
  if type(settings) ~= "table" then
    fail("direct preview case settings must be a table", 2)
  end
  local ignore_case = require_case_setting(settings, "ignore_case")
  local smart_case = require_case_setting(settings, "smart_case")
  local selected_occurrence = self:normalize_count(count)
  local counters = {}
  local positions = {}
  local resolver = planner_records[self].case_resolver
  for _, record in ipairs(self:scan_for_descriptor(view, origin, descriptor)) do
    local selected
    if ignore_case then
      selected = increment_counter(
        counters,
        resolver:lowercase(record.character)
      ) == selected_occurrence
    elseif smart_case then
      selected = increment_smart_counters(
        counters,
        record.character
      ) == selected_occurrence
    else
      selected = increment_counter(
        counters,
        record.character
      ) == selected_occurrence
    end
    if selected then
      positions[#positions + 1] = record.position
    end
  end
  return positions
end

function M.new(options)
  return DirectPreviewPlanner.new(options)
end

function M.scan_current_line(view, origin, direction)
  return DirectPreviewPlanner.new():scan_current_line(view, origin, direction)
end

function M.scan_for_descriptor(view, origin, descriptor)
  return DirectPreviewPlanner.new():scan_for_descriptor(view, origin, descriptor)
end

function M.plan(view, origin, descriptor, count, settings, options)
  return DirectPreviewPlanner.new(options):plan(
    view,
    origin,
    descriptor,
    count,
    settings
  )
end

setmetatable(M, {
  __call = function(_, options)
    return DirectPreviewPlanner.new(options)
  end,
})

return M