/*
 *     Copyright 2021-Present Couchbase, Inc.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */

#pragma once

#include "core/transactions/error_class.hxx"
#include "core/transactions/exceptions.hxx"
#include "core/transactions/result.hxx"
#include "transaction_context.hxx"

#include <couchbase/transaction_op_error_context.hxx>

#include <algorithm>
#include <list>

namespace couchbase::core::transactions
{
//  only used in ambiguity resolution during atr_commit
class retry_atr_commit : public std::runtime_error
{
  public:
    retry_atr_commit(const std::string& what)
      : std::runtime_error(what)
    {
    }
};

class retry_operation : public std::runtime_error
{
  public:
    retry_operation(const std::string& what)
      : std::runtime_error(what)
    {
    }
};

class retry_operation_timeout : public std::runtime_error
{
  public:
    retry_operation_timeout(const std::string& what)
      : std::runtime_error(what)
    {
    }
};

class retry_operation_retries_exhausted : public std::runtime_error
{
  public:
    retry_operation_retries_exhausted(const std::string& what)
      : std::runtime_error(what)
    {
    }
};

external_exception
external_exception_from_error_class(error_class ec);

template<typename OStream>
OStream&
operator<<(OStream& os, const error_class& ec)
{
    switch (ec) {
        case FAIL_HARD:
            os << "FAIL_HARD";
            break;
        case FAIL_OTHER:
            os << "FAIL_OTHER";
            break;
        case FAIL_TRANSIENT:
            os << "FAIL_TRANSIENT";
            break;
        case FAIL_AMBIGUOUS:
            os << "FAIL_AMBIGUOUS";
            break;
        case FAIL_DOC_ALREADY_EXISTS:
            os << "FAIL_DOC_ALREADY_EXISTS";
            break;
        case FAIL_DOC_NOT_FOUND:
            os << "FAIL_DOC_NOT_FOUND";
            break;
        case FAIL_PATH_NOT_FOUND:
            os << "FAIL_PATH_NOT_FOUND";
            break;
        case FAIL_CAS_MISMATCH:
            os << "FAIL_CAS_MISMATCH";
            break;
        case FAIL_WRITE_WRITE_CONFLICT:
            os << "FAIL_WRITE_WRITE_CONFLICT";
            break;
        case FAIL_ATR_FULL:
            os << "FAIL_ATR_FULL";
            break;
        case FAIL_PATH_ALREADY_EXISTS:
            os << "FAIL_PATH_ALREADY_EXISTS";
            break;
        case FAIL_EXPIRY:
            os << "FAIL_EXPIRY";
            break;
        default:
            os << "UNKNOWN ERROR CLASS";
            break;
    }
    return os;
}
enum final_error { FAILED, EXPIRED, FAILED_POST_COMMIT, AMBIGUOUS };

error_class
error_class_from_result(const result& res);

class client_error : public std::runtime_error
{
  private:
    error_class ec_;
    std::optional<result> res_;

  public:
    explicit client_error(const result& res)
      : runtime_error(res.strerror())
      , ec_(error_class_from_result(res))
      , res_(res)
    {
    }
    explicit client_error(error_class ec, const std::string& what)
      : runtime_error(what)
      , ec_(ec)
    {
    }
    error_class ec() const
    {
        return ec_;
    }
    std::optional<result> res() const
    {
        return res_;
    }
};

// Prefer this as it reads better than throw client_error(FAIL_EXPIRY, ...)
class attempt_expired : public client_error
{
  public:
    attempt_expired(const std::string& what)
      : client_error(FAIL_EXPIRY, what)
    {
    }
};

/**
 * All exceptions within a transaction are, or are converted to, an exception
 * derived from this.  The transaction logic then consumes them to decide to
 * retry, or rollback the transaction.
 */
class transaction_operation_failed : public std::runtime_error
{
  public:
    explicit transaction_operation_failed(error_class ec, const std::string& what)
      : std::runtime_error(what)
      , ec_(ec)
      , retry_(false)
      , rollback_(true)
      , to_raise_(FAILED)
      , cause_(external_exception_from_error_class(ec))
    {
    }
    explicit transaction_operation_failed(const client_error& client_err)
      : std::runtime_error(client_err.what())
      , ec_(client_err.ec())
      , retry_(false)
      , rollback_(true)
      , to_raise_(FAILED)
      , cause_(UNKNOWN)
    {
    }

    static transaction_operation_failed merge_errors(std::list<transaction_operation_failed> errors,
                                                     std::optional<external_exception> cause = {},
                                                     bool do_throw = true)
    {
        // default would be to set retry false, rollback true.  If
        // _all_ errors set retry to true, we set retry to true.  If _any_ errors
        // set rollback to false, we set rollback to false.
        // For now lets retain the ec, to_raise, and cause for the first of the
        // retries (if they all are true), or the first of the rollbacks, if it
        // is false.  Not rolling back takes precedence over retry.  Otherwise, we
        // just retain the first.
        assert(errors.size() > 0);
        // start with first error that isn't previous_operation_failed
        auto error_to_throw = *(std::find_if(
          errors.begin(), errors.end(), [](auto& err) { return err.cause() != external_exception::PREVIOUS_OPERATION_FAILED; }));
        for (auto& ex : errors) {
            if (ex.cause() == external_exception::PREVIOUS_OPERATION_FAILED) {
                continue;
            }
            if (!ex.retry_) {
                error_to_throw = ex;
            }
            if (!ex.rollback_) {
                // this takes precedence, (no_rollback means no_retry as well), so just throw this
                error_to_throw = ex;
                break;
            }
        }
        if (cause) {
            error_to_throw.cause(*cause);
        }
        if (do_throw) {
            throw error_to_throw;
        }
        return error_to_throw;
    }
    // Retry is false by default, this makes it true
    transaction_operation_failed& retry()
    {
        retry_ = true;
        return *this;
    }

    // Rollback defaults to true, this sets it to false
    transaction_operation_failed& no_rollback()
    {
        rollback_ = false;
        return *this;
    }

    // Defaults to FAILED, this sets it to EXPIRED
    transaction_operation_failed& expired()
    {
        to_raise_ = EXPIRED;
        return *this;
    }

    // Defaults to FAILED, sets to FAILED_POST_COMMIT
    transaction_operation_failed& failed_post_commit()
    {
        to_raise_ = FAILED_POST_COMMIT;
        return *this;
    }

    // Defaults to FAILED, sets AMBIGUOUS
    transaction_operation_failed& ambiguous()
    {
        to_raise_ = AMBIGUOUS;
        return *this;
    }

    transaction_operation_failed& cause(external_exception cause)
    {
        cause_ = cause;
        return *this;
    }

    bool should_rollback() const
    {
        return rollback_;
    }

    bool should_retry() const
    {
        return retry_;
    }

    external_exception cause() const
    {
        return cause_;
    }

    void do_throw(const transaction_context& context) const
    {
        if (to_raise_ == FAILED_POST_COMMIT) {
            return;
        }
        switch (to_raise_) {
            case EXPIRED:
                throw transaction_exception(*this, context, failure_type::EXPIRY);
            case AMBIGUOUS:
                throw transaction_exception(*this, context, failure_type::COMMIT_AMBIGUOUS);
            default:
                throw transaction_exception(*this, context, failure_type::FAIL);
        }
    }

    std::optional<transaction_exception> get_final_exception(const transaction_context& context) const
    {
        {

            switch (to_raise_) {
                case EXPIRED:
                    return transaction_exception(*this, context, failure_type::EXPIRY);
                case AMBIGUOUS:
                    return transaction_exception(*this, context, failure_type::COMMIT_AMBIGUOUS);
                case FAILED_POST_COMMIT:
                    return std::nullopt;
                default:
                    return transaction_exception(*this, context, failure_type::FAIL);
            }
        }
    }

    transaction_op_error_context get_error_ctx() const
    {
        errc::transaction_op ec = transaction_op_errc_from_external_exception(cause_);
        return { ec };
    }

  private:
    error_class ec_;
    bool retry_;
    bool rollback_;
    final_error to_raise_;
    external_exception cause_;
};

namespace internal
{
/**
 * Used only in testing: injects an error that will be handled as FAIL_HARD.
 *
 * This is not an error class the transaction library would ever raise
 * voluntarily.  It is designed to simulate an application crash or similar. The
 * transaction will not rollback and will stop abruptly.
 *
 * However, for testing purposes, a TransactionFailed will still be raised,
 * correct in all respects including the attempts field.
 */
class test_fail_hard : public client_error
{
  public:
    explicit test_fail_hard()
      : client_error(FAIL_HARD, "Injecting a FAIL_HARD error")
    {
    }
};

/**
 * Used only in testing: injects an error that will be handled as
 * FAIL_AMBIGUOUS.
 *
 * E.g. either the server or SDK raised an error indicating the operation was
 * ambiguously successful.
 */
class test_fail_ambiguous : public client_error
{
  public:
    explicit test_fail_ambiguous()
      : client_error(FAIL_AMBIGUOUS, "Injecting a FAIL_AMBIGUOUS error")
    {
    }
};

/**
 * Used only in testing: injects an error that will be handled as
 * FAIL_TRANSIENT.
 *
 * E.g. a transient server error that could be recovered with a retry of either
 * the operation or the transaction.
 */
class test_fail_transient : public client_error
{
  public:
    explicit test_fail_transient()
      : client_error(FAIL_TRANSIENT, "Injecting a FAIL_TRANSIENT error")
    {
    }
};

/**
 * Used only in testing: injects an error that will be handled as FAIL_OTHER.
 *
 * E.g. an error which is not retryable.
 */
class test_fail_other : public client_error
{
  public:
    explicit test_fail_other()
      : client_error(FAIL_OTHER, "Injecting a FAIL_OTHER error")
    {
    }
};
} // namespace internal
} // namespace couchbase::core::transactions