local case_policy = require("clever_tee.case_policy")
local domain = require("clever_tee.domain")
local migemo_catalog = require("clever_tee.migemo_catalog")
local text_topology = require("clever_tee.text_topology")

local M = {}
local TargetPlanFactory = {}
M.TargetPlanFactory = TargetPlanFactory

M.SYMBOLS = "!\"#$%&'()=~|\\-^@`[]{};:+*<>,.?_/"

local SYMBOL_CHARACTERS = {}
local SYMBOL_SET = {}
for index = 1, #M.SYMBOLS do
  local character = M.SYMBOLS:sub(index, index)
  SYMBOL_CHARACTERS[index] = character
  SYMBOL_SET[character] = true
end

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

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

local function require_target(target)
  if not domain.TargetValue.is(target) then
    fail("target plan target must be a TargetValue", 2)
  end
  return target
end

local function require_boolean(value, name)
  if type(value) ~= "boolean" then
    fail("match policy " .. name .. " must be a Boolean", 2)
  end
  return value
end

local function require_string(value, name)
  if type(value) ~= "string" then
    fail("match policy " .. name .. " must be a string", 2)
  end
  return value
end

local function copy_list(values)
  local result = {}
  for index = 1, #values do
    result[index] = values[index]
  end
  return result
end

function M.symbol_characters()
  return copy_list(SYMBOL_CHARACTERS)
end

function M.is_symbol(character)
  return type(character) == "string" and SYMBOL_SET[character] == true
end

local function require_character_list(characters, source)
  if type(characters) ~= "table" then
    fail("editor character splitter must return a list", 3)
  end

  local result = {}
  local item_count = 0
  for key, character in pairs(characters) do
    if type(key) ~= "number"
      or key ~= math.floor(key)
      or key < 1
      or key > #characters
      or type(character) ~= "string"
      or character == ""
    then
      fail("editor character splitter must return a list of nonempty strings", 3)
    end
    result[key] = character
    item_count = item_count + 1
  end
  if item_count ~= #characters or table.concat(result) ~= source then
    fail("editor character splitter must preserve the configured trigger string", 3)
  end
  return result
end

function M.parse_trigger_characters(value, splitter)
  if type(value) ~= "string" then
    fail("chars_match_any_signs must be a string", 2)
  end
  splitter = splitter or text_topology.split_editor_characters
  if type(splitter) ~= "function" then
    fail("editor character splitter must be a function", 2)
  end
  return require_character_list(splitter(value), value)
end

local function trigger_set(value, splitter)
  local result = {}
  for _, character in ipairs(M.parse_trigger_characters(value, splitter)) do
    result[character] = true
  end
  return result
end

local function false_matcher()
  return false
end

local function symbol_matcher(candidate_character)
  return M.is_symbol(candidate_character)
end

local function normalize_factory_options(options)
  if options == nil then
    return {}
  end
  if type(options) == "function" then
    return { lowercase = options }
  end
  if type(options) ~= "table" then
    fail("TargetPlanFactory options must be a table", 3)
  end
  if type(options.sample_match) == "function"
    and options.policy == nil
    and options.policy_service == nil
    and options.case_resolver == nil
    and options.lowercase == nil
    and options.splitter == nil
    and options.split_editor_characters == nil
  then
    return { policy = options }
  end
  return options
end

local function require_policy_service(service)
  if service ~= nil and (type(service) ~= "table"
      or type(service.sample_match) ~= "function")
  then
    fail("TargetPlanFactory policy must provide sample_match", 3)
  end
  return service
end

local function require_case_resolver(resolver, options)
  if resolver == nil then
    return case_policy.new({
      lowercase = options.lowercase,
    })
  end
  if type(resolver) ~= "table"
    or type(resolver.resolve) ~= "function"
    or type(resolver.comparator) ~= "function"
  then
    fail("TargetPlanFactory case resolver is invalid", 3)
  end
  return resolver
end

local function require_splitter(splitter)
  splitter = splitter or text_topology.split_editor_characters
  if type(splitter) ~= "function" then
    fail("TargetPlanFactory editor character splitter must be a function", 3)
  end
  return splitter
end

local function require_migemo_catalog(catalog)
  if catalog ~= nil and not migemo_catalog.MigemoCatalog.is(catalog) then
    fail("TargetPlanFactory migemo_catalog must be a MigemoCatalog", 3)
  end
  return catalog
end

local factory_metatable = {
  __index = TargetPlanFactory,
  __newindex = function()
    fail("TargetPlanFactory values are immutable", 2)
  end,
  __tostring = function()
    return "target-plan-factory"
  end,
  __metatable = "clever_tee.target_plan.TargetPlanFactory",
}

function TargetPlanFactory.new(options)
  if TargetPlanFactory.is(options) then
    return options
  end
  options = normalize_factory_options(options)
  local factory = setmetatable({}, factory_metatable)
  factory_records[factory] = {
    policy = require_policy_service(options.policy or options.policy_service),
    case_resolver = require_case_resolver(options.case_resolver, options),
    splitter = require_splitter(
      options.split_editor_characters or options.splitter
    ),
    migemo_catalog = require_migemo_catalog(
      options.migemo_catalog or options.catalog
    ),
  }
  return factory
end

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

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

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

local function default_match_policy()
  return {
    ignore_case = false,
    smart_case = false,
    use_migemo = false,
    chars_match_any_signs = "",
  }
end

local function sampled_policy(factory, target, match_policy)
  local service
  if match_policy == nil then
    service = factory_records[factory].policy
    if service == nil then
      return default_match_policy()
    end
  elseif type(match_policy) == "table"
    and type(match_policy.sample_match) == "function"
  then
    service = match_policy
  end

  if service ~= nil then
    match_policy = service:sample_match(target)
  end
  if type(match_policy) ~= "table" then
    fail("target match policy must be a table", 3)
  end

  local use_migemo = match_policy.use_migemo
  if use_migemo == nil then
    use_migemo = false
  end

  return {
    ignore_case = require_boolean(match_policy.ignore_case, "ignore_case"),
    smart_case = require_boolean(match_policy.smart_case, "smart_case"),
    use_migemo = require_boolean(use_migemo, "use_migemo"),
    chars_match_any_signs = require_string(
      match_policy.chars_match_any_signs,
      "chars_match_any_signs"
    ),
  }
end

local function new_plan(target, kind, case_mode, matcher)
  return domain.TargetPlan.new({
    target = target,
    kind = kind,
    case_mode = case_mode,
    matcher = matcher,
  })
end

local function is_ascii_alphabetic(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"))
    or (code >= string.byte("A") and code <= string.byte("Z"))
end

M.is_ascii_alphabetic = is_ascii_alphabetic

local function context_field(context, primary, alternate)
  local value = context[primary]
  if value == nil and alternate ~= nil then
    value = context[alternate]
  end
  return value
end

local function context_table(match_policy, search_context)
  if text_topology.TextView.is(search_context) then
    return { text_view = search_context }
  end
  if search_context ~= nil and type(search_context) ~= "table" then
    fail("target search context must be a table or TextView", 3)
  end

  local context = search_context or {}
  if search_context == nil and type(match_policy) == "table" then
    if match_policy.text_view ~= nil
      or match_policy.view ~= nil
      or match_policy.search_scope ~= nil
      or match_policy.scope ~= nil
      or match_policy.origin ~= nil
      or match_policy.current_line ~= nil
      or match_policy.effective_encoding ~= nil
      or match_policy.encoding ~= nil
    then
      context = match_policy
    end
  end
  return context
end

local function active_policy_service(factory, match_policy)
  if type(match_policy) == "table"
    and type(match_policy.sample_match) == "function"
  then
    return match_policy
  end
  return factory_records[factory].policy
end

local function search_scope(factory, match_policy, context)
  local value = context_field(context, "search_scope", "scope")
  if value == nil and type(match_policy) == "table" then
    value = match_policy.search_scope
    if value == nil and match_policy.search_current_line_only ~= nil then
      value = match_policy.search_current_line_only
          and domain.SearchScope.CURRENT_LINE
        or domain.SearchScope.BUFFER
    end
  end
  if value == nil then
    local service = active_policy_service(factory, match_policy)
    if service ~= nil and type(service.sample_search) == "function" then
      value = service:sample_search().search_scope
    end
  end
  if value == nil then
    return domain.SearchScope.BUFFER
  end
  if value == "line" then
    value = domain.SearchScope.CURRENT_LINE
  end
  return domain.SearchScope.from_string(value)
end

local function migemo_search_context(factory, match_policy, search_context)
  local context = context_table(match_policy, search_context)
  local view = context_field(context, "text_view", "view")
  if not text_topology.TextView.is(view) then
    fail("Migemo target planning requires a TextView", 3)
  end

  local scope = search_scope(factory, match_policy, context)
  local origin = context.origin
  if origin == nil then
    origin = context.current_line
  end
  if scope == domain.SearchScope.CURRENT_LINE and origin == nil then
    fail("current-line Migemo planning requires an origin line", 3)
  end

  local line_number
  if scope == domain.SearchScope.CURRENT_LINE then
    line_number = type(origin) == "number"
        and origin
      or domain.Position.coerce(origin).line
  end

  local encoding = context_field(context, "effective_encoding", "encoding")
    or view.requested_encoding
    or view.effective_encoding
  return {
    view = view,
    scope = scope,
    origin = origin,
    line_number = line_number,
    encoding = encoding,
    bounds = view:match_start_bounds(scope, origin),
  }
end

local function selected_migemo_catalog(factory, match_policy)
  local record = factory_records[factory]
  if record.migemo_catalog == nil then
    record.migemo_catalog = migemo_catalog.new({
      policy = active_policy_service(factory, match_policy),
    })
  end
  return record.migemo_catalog
end

local function migemo_matcher(
  target_character,
  case_mode,
  resolver,
  dictionary,
  context
)
  local target_equal = resolver:comparator(target_character, case_mode)
  local assertion = dictionary:predicate(target_character, case_mode)

  return function(candidate_character, candidate_position, candidate_view)
    if candidate_position == nil then
      fail("Migemo matching requires a candidate Position", 2)
    end
    local position = domain.Position.coerce(candidate_position)
    local view = candidate_view or context.view
    if not text_topology.TextView.is(view) then
      fail("Migemo matching requires a TextView", 2)
    end
    if not context.bounds:contains(position)
      or not view:is_character_start(position)
    then
      return false
    end

    local actual_character = view:character_at(position)
    if candidate_character ~= actual_character then
      return false
    end
    if is_ascii_alphabetic(actual_character)
      and not target_equal(actual_character)
    then
      return false
    end
    return assertion(view:text_suffix(position))
  end
end

function TargetPlanFactory:build(target, match_policy, search_context)
  target = require_target(target)
  local record = factory_records[self]
  local sampled = sampled_policy(self, target, match_policy)
  local case_mode = record.case_resolver:resolve(
    target,
    sampled.ignore_case,
    sampled.smart_case
  )

  if target.first_code == 0x80 then
    return new_plan(
      target,
      domain.TargetPlanKind.EMPTY,
      case_mode,
      false_matcher
    )
  end

  if sampled.use_migemo and is_ascii_alphabetic(target.value) then
    local context = migemo_search_context(self, match_policy, search_context)
    local active = context.scope == domain.SearchScope.BUFFER
      or context.view:line_byte_length(context.line_number)
        > context.view:line_character_count(context.line_number)
    if active then
      local dictionary = selected_migemo_catalog(self, match_policy):get(
        context.encoding,
        active_policy_service(self, match_policy)
      )
      return new_plan(
        target,
        domain.TargetPlanKind.MIGEMO,
        case_mode,
        migemo_matcher(
          target.value,
          case_mode,
          record.case_resolver,
          dictionary,
          context
        )
      )
    end
  end

  local triggers = trigger_set(sampled.chars_match_any_signs, record.splitter)
  if triggers[target.value] then
    return new_plan(
      target,
      domain.TargetPlanKind.SYMBOL,
      case_mode,
      symbol_matcher
    )
  end

  local kind = target.value == "\\"
      and domain.TargetPlanKind.BACKSLASH
    or domain.TargetPlanKind.LITERAL
  return new_plan(
    target,
    kind,
    case_mode,
    record.case_resolver:comparator(target.value, case_mode)
  )
end

local function is_search_context(value)
  return text_topology.TextView.is(value)
    or (type(value) == "table" and (
      value.text_view ~= nil
      or value.view ~= nil
      or value.search_scope ~= nil
      or value.scope ~= nil
      or value.origin ~= nil
      or value.current_line ~= nil
      or value.effective_encoding ~= nil
      or value.encoding ~= nil
    ))
end

function M.build(target, match_policy, options, search_context)
  if search_context == nil and is_search_context(options) then
    search_context = options
    options = nil
  end
  return TargetPlanFactory.new(options):build(
    target,
    match_policy,
    search_context
  )
end

function M.build_for_view(target, view, origin, scope, match_policy, options)
  return TargetPlanFactory.new(options):build(target, match_policy, {
    text_view = view,
    origin = origin,
    search_scope = scope,
  })
end

M.create = M.build
M.create_plan = M.build
M.SYMBOL_SET_STRING = M.SYMBOLS

return M