local log = require "kong.cmd.utils.log"


local MIGRATIONS_MUTEX_KEY = "migrations"
local NOT_LEADER_MSG = "aborted: another node is performing database changes"
local NEEDS_BOOTSTRAP_MSG = "Database needs bootstrapping or is older than Kong 1.0.\n\n" ..
  "To start a new installation from scratch, run 'kong migrations bootstrap'.\n\n" ..
  "To migrate from a version older than 1.0, migrated to Kong 1.5.0 first. \n" ..
  "If you still have 'apis' entities, you can convert them to Routes and Services\n" ..
  "using the 'kong migrations migrate-apis' command in Kong 1.5.0.\n\n"


local function check_state(schema_state)
  if not schema_state:is_up_to_date() then
    if schema_state.needs_bootstrap then
      error(NEEDS_BOOTSTRAP_MSG)
    end

    if schema_state.new_migrations then
      error("New migrations available; run 'kong migrations up' to proceed")
    end
  end
end

local function bootstrap(schema_state, db, ttl)
  if schema_state.needs_bootstrap then
    log("Bootstrapping database...")
    assert(db:schema_bootstrap())

  else
    log("Database already bootstrapped")
    return
  end

  local opts = {
    ttl = ttl,
    no_wait = true, -- exit the mutex if another node acquired it
  }

  local ok, err = db:cluster_mutex(MIGRATIONS_MUTEX_KEY, opts, function()
    assert(db:run_migrations(schema_state.new_migrations, {
      run_up = true,
      run_teardown = true,
    }))
    log("Database is up-to-date")
  end)
  if err then
    error(err)
  end

  if not ok then
    log(NOT_LEADER_MSG)
  end
end


local function up(schema_state, db, opts)
  if schema_state.needs_bootstrap then
    -- fresh install: must bootstrap (which will run migrations up)
    error("Cannot run migrations: " .. NEEDS_BOOTSTRAP_MSG)
  end

  -- see #6105 for background, this is a workaround that gives a better
  -- error message (one w/o the long stacktrace) when the pending
  -- migration checks failed
  if not opts.force and schema_state.pending_migrations then
    error("Database has pending migrations; run 'kong migrations finish'")
  end

  local ok, err = db:cluster_mutex(MIGRATIONS_MUTEX_KEY, opts, function()
    schema_state = assert(db:schema_state())

    if not opts.force and schema_state.pending_migrations then
      error("Database has pending migrations; run 'kong migrations finish'")
    end

    if opts.force and schema_state.executed_migrations then
      log.debug("forcing re-execution of these migrations:\n%s",
                schema_state.executed_migrations)

      assert(db:run_migrations(schema_state.executed_migrations, {
        run_up = true,
        run_teardown = true,
        skip_teardown_migrations = schema_state.pending_migrations
      }))

      schema_state = assert(db:schema_state())
      if schema_state.pending_migrations then
        log("\nDatabase has pending migrations; run 'kong migrations finish' when ready")
        return
      end
    end

    if not schema_state.new_migrations then
      if not opts.force then
        log("Database is already up-to-date")
      end

      return
    end

    log.debug("migrations to run:\n%s", schema_state.new_migrations)

    assert(db:run_migrations(schema_state.new_migrations, {
      run_up = true,
    }))

    schema_state = assert(db:schema_state())
    if schema_state.pending_migrations then
      log("\nDatabase has pending migrations; run 'kong migrations finish' when ready")
      return
    end
  end)
  if err then
    error(err)
  end

  if not ok then
    log(NOT_LEADER_MSG)
  end

  return ok
end


local function finish(schema_state, db, opts)
  if schema_state.needs_bootstrap then
    error("Cannot run migrations: " .. NEEDS_BOOTSTRAP_MSG)
  end

  opts.no_wait = true -- exit the mutex if another node acquired it

  local ok, err = db:cluster_mutex(MIGRATIONS_MUTEX_KEY, opts, function()
    local schema_state = assert(db:schema_state())

    if opts.force and schema_state.executed_migrations then
      assert(db:run_migrations(schema_state.executed_migrations, {
        run_up = true,
        run_teardown = true,
      }))

      schema_state = assert(db:schema_state())
    end

    if schema_state.pending_migrations then
      log.debug("pending migrations to finish:\n%s",
                schema_state.pending_migrations)

      assert(db:run_migrations(schema_state.pending_migrations, {
        run_teardown = true,
      }))

      schema_state = assert(db:schema_state())
    end

    if schema_state.new_migrations then
      log("\nNew migrations available; run 'kong migrations up' to proceed")
      return
    end

    if not opts.force and not schema_state.pending_migrations then
      log("No pending migrations to finish")
    end

    return
  end)
  if err then
    error(err)
  end

  if not ok then
    log(NOT_LEADER_MSG)
  end
end


local function reset(schema_state, db, ttl)
  if schema_state.needs_bootstrap then
    log("Database not bootstrapped, nothing to reset")
    return false
  end

  local opts = {
    ttl = ttl,
    no_wait = true,
    no_cleanup = true,
  }

  local ok, err = db:cluster_mutex(MIGRATIONS_MUTEX_KEY, opts, function()
    log("Resetting database...")
    assert(db:schema_reset())
    log("Database successfully reset")
  end)
  if err then
    -- failed to acquire locks - maybe locks table was dropped?
    log.error(err .. " - retrying without cluster lock")
    log("Resetting database...")
    -- ROLLBACK in order to solve this error
    -- ERROR: current transaction is aborted, commands ignored until end of transaction block
    assert(db.connector:query("ROLLBACK;"))
    assert(db:schema_reset())
    log("Database successfully reset")
    return true
  end

  if not ok then
    log(NOT_LEADER_MSG)
    return false
  end
  return true
end


return {
  up = up,
  reset = reset,
  finish = finish,
  bootstrap = bootstrap,
  check_state = check_state,
  NEEDS_BOOTSTRAP_MSG = NEEDS_BOOTSTRAP_MSG,
}