/**
 * @file pgsql-transaction_variable_state_tracking-t.cpp
 * @brief TAP test validating PostgreSQL session parameter behavior in transactions.
 * Tests rollback/commit/savepoint behavior for session variables to ensure state consistency.
 */

#include <unistd.h>
#include <string>
#include <sstream>
#include <chrono>
#include <thread>
#include "libpq-fe.h"
#include "command_line.h"
#include "tap.h"
#include "utils.h"

CommandLine cl;

using PGConnPtr = std::unique_ptr<PGconn, decltype(&PQfinish)>;
using PGResultPtr = std::unique_ptr<PGresult, decltype(&PQclear)>;

enum ConnType {
    ADMIN,
    BACKEND
};

PGConnPtr createNewConnection(ConnType conn_type, const std::string& options = "", bool with_ssl = false) {
    
    const char* host = (conn_type == BACKEND) ? cl.pgsql_host : cl.pgsql_admin_host;
    int port = (conn_type == BACKEND) ? cl.pgsql_port : cl.pgsql_admin_port;
    const char* username = (conn_type == BACKEND) ? cl.pgsql_root_username : cl.admin_username;
    const char* password = (conn_type == BACKEND) ? cl.pgsql_root_password : cl.admin_password;

    std::stringstream ss;

    ss << "host=" << host << " port=" << port;
    ss << " user=" << username << " password=" << password;
    ss << (with_ssl ? " sslmode=require" : " sslmode=disable");

    if (options.empty() == false) {
		ss << " options='" << options << "'";
    }

    PGconn* conn = PQconnectdb(ss.str().c_str());
    if (PQstatus(conn) != CONNECTION_OK) {
        fprintf(stderr, "Connection failed to '%s': %s", (conn_type == BACKEND ? "Backend" : "Admin"), PQerrorMessage(conn));
        PQfinish(conn);
        return PGConnPtr(nullptr, &PQfinish);
    }
    return PGConnPtr(conn, &PQfinish);
}

struct TestCase {
    std::string name;
    std::function<bool()> test_fn;
    bool should_fail;
};

struct TestVariable {
    std::string name;
    std::vector<std::string> test_values;
};

std::vector<TestCase> tests;

PGResultPtr executeQuery(PGconn* conn, const std::string& query) {
    diag("Executing: %s", query.c_str());
    PGresult* res = PQexec(conn, query.c_str());
    if (PQresultStatus(res) != PGRES_COMMAND_OK && PQresultStatus(res) != PGRES_TUPLES_OK) {
        diag("Query failed: %s", PQerrorMessage(conn));
    }
    return PGResultPtr(res, &PQclear);
}

std::string getVariable(PGconn* conn, const std::string& var) {
    auto res = executeQuery(conn, ("SHOW " + var));
    const std::string& val = std::string(PQgetvalue(res.get(), 0, 0));
    diag(">> '%s' = '%s'", var.c_str(), val.c_str());
    return val;
}

void reset_variable(PGconn* conn, const std::string& var, const std::string& original) {
    executeQuery(conn, "SET " + var + " = " + original);
}

void add_test(const std::string& name, std::function<bool()> fn, bool should_fail = false) {
    tests.push_back({ name, fn, should_fail });
}

void run_tests() {
    
    for (const auto& test : tests) {
        bool result = false;

        try {
            result = test.test_fn();
            if (test.should_fail) result = !result;
        }
        catch (const std::exception& e) {
            result = false;
        }

		ok(result, "Test:%s should %s", test.name.c_str(), test.should_fail ? "FAIL" : "PASS");
    }
}

// Common test scenarios
bool test_transaction_rollback(const TestVariable& var) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    const auto original = getVariable(conn.get(), var.name);

    bool success = true;

    for (const auto& val : var.test_values) {
        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "ROLLBACK");

        success = getVariable(conn.get(), var.name) == original;
        if (!success)
            break;
    }

    return success;
}

bool test_transaction_abort(const TestVariable& var) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    const auto original = getVariable(conn.get(), var.name);

    bool success = true;

    for (const auto& val : var.test_values) {
        executeQuery(conn.get(), "START TRANSACTION");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "ABORT");

        success = getVariable(conn.get(), var.name) == original;
        if (!success)
            break;
    }
    return success;
}

bool test_savepoint_rollback(const TestVariable& var) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    const auto original = getVariable(conn.get(), var.name);

    bool success = true;

    for (const auto& val : var.test_values) {
        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SAVEPOINT sp1");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "ROLLBACK TO sp1");
        executeQuery(conn.get(), "COMMIT");

        success = getVariable(conn.get(), var.name) == original;
        if (!success)
            break;
    }
    return success;
}

bool test_transaction_commit(const TestVariable& var, const std::map<std::string, std::string>& original_values) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    
    bool success = true;
    
    for (const auto& val : var.test_values) {
        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "COMMIT");

        success = getVariable(conn.get(), var.name) == val;
        if (!success)
            break;
    }
    reset_variable(conn.get(), var.name, original_values.at(var.name));
    return success;
}

bool test_savepoint_commit(const TestVariable& var, const std::map<std::string, std::string>& original_values) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    bool success = true;

    for (const auto& val : var.test_values) {
        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SAVEPOINT sp1");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "RELEASE SAVEPOINT sp1");
        executeQuery(conn.get(), "COMMIT");

        success = getVariable(conn.get(), var.name) == val;
        if (!success)
            break;
    }
    reset_variable(conn.get(), var.name, original_values.at(var.name));
    return success;
}

bool test_savepoint_release_commit(const TestVariable& var, const std::map<std::string, std::string>& original_values) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    const auto original = getVariable(conn.get(), var.name);
    executeQuery(conn.get(), "BEGIN");
    executeQuery(conn.get(), "SET " + var.name + " = " + var.test_values[0]);
    executeQuery(conn.get(), "SAVEPOINT sp1");
    executeQuery(conn.get(), "SET " + var.name + " = " + var.test_values[1]);
    executeQuery(conn.get(), "RELEASE SAVEPOINT sp1");
    executeQuery(conn.get(), "COMMIT");
    const bool success = getVariable(conn.get(), var.name) == var.test_values[1];
    reset_variable(conn.get(), var.name, original_values.at(var.name));
    return success;
}

bool has_warnings = false;

void notice_processor(void* arg, const char* message) {
    diag("NOTICE: %s", message);
	has_warnings = true;
}

bool test_transaction_rollback_and_chain(const TestVariable& var) {
    auto conn = createNewConnection(ConnType::BACKEND, "", false);
    PQsetNoticeProcessor(conn.get(), notice_processor, NULL);

    const auto original = getVariable(conn.get(), var.name);

    bool success = true;

    for (const auto& val : var.test_values) {

        executeQuery(conn.get(), "START TRANSACTION");
        executeQuery(conn.get(), "SET " + var.name + " = " + val);
        executeQuery(conn.get(), "ROLLBACK AND CHAIN");

		char tran_stat = PQtransactionStatus(conn.get());

        if (tran_stat != PQTRANS_INTRANS) {
            diag("Expected transaction status INTRANS after ROLLBACK AND CHAIN, got %d", tran_stat);
            success = false;
            break;
		}

        success = getVariable(conn.get(), var.name) == original;
        if (success) {
            executeQuery(conn.get(), "ROLLBACK");
            tran_stat = PQtransactionStatus(conn.get());
            if (tran_stat != PQTRANS_IDLE) {
                diag("Expected transaction status IDLE after ROLLBACK, got %d", tran_stat);
                success = false;
                break;
            }

            if (has_warnings == false)
                success = getVariable(conn.get(), var.name) == original;
            else
                success = false;
        }
        if (!success)
            break;
    }

    return success;
}

int main(int argc, char** argv) {

    if (cl.getEnv())
        return exit_status();

    std::map<std::string, std::string> original_values;
    std::map<std::string, TestVariable> tracked_vars = {
        {"client_encoding", {"client_encoding", {"LATIN1", "UTF8"}}},
        {"datestyle", {"datestyle", {"ISO, MDY", "SQL, DMY"}}},
        {"intervalstyle", {"intervalstyle", {"postgres", "iso_8601"}}},
        {"standard_conforming_strings", {"standard_conforming_strings", {"on", "off"}}},
        {"timezone", {"timezone", {"UTC", "PST8PDT"}}},
        {"bytea_output", {"bytea_output", {"hex", "escape"}}},
        {"allow_in_place_tablespaces", {"allow_in_place_tablespaces", {"on", "off"}}},
        {"enable_bitmapscan", {"enable_bitmapscan", {"on", "off"}}},
        {"enable_hashjoin", {"enable_hashjoin", {"on", "off"}}},
        {"enable_indexscan", {"enable_indexscan", {"on", "off"}}},
        {"enable_nestloop", {"enable_nestloop", {"on", "off"}}},
        {"enable_seqscan", {"enable_seqscan", {"on", "off"}}},
        {"enable_sort", {"enable_sort", {"on", "off"}}},
        {"escape_string_warning", {"escape_string_warning", {"on", "off"}}},
        {"synchronous_commit", {"synchronous_commit", {"on", "off"}}},
        {"extra_float_digits", {"extra_float_digits", {"0", "3"}}},
        {"client_min_messages", {"client_min_messages", {"notice", "warning"}}}
    };


    PGConnPtr conn = createNewConnection(ConnType::BACKEND, "", false);
    if (!conn || PQstatus(conn.get()) != CONNECTION_OK) {
        BAIL_OUT("Error: failed to connect to the database in file %s, line %d", __FILE__, __LINE__);
        return exit_status();
    }

    // Store original values
    for (const auto& [name, var] : tracked_vars) {
        original_values[name] = getVariable(conn.get(), name);
    }


    // Add generic tests
    add_test("Commit without transaction should fail", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        PGresult* res = PQexec(conn.get(), "COMMIT");
        const bool failed = PQresultStatus(res) != PGRES_COMMAND_OK;
        PQclear(res);
        return failed;
        }, true);

    // Add variable-specific tests using containers
    for (const auto& [name, var] : tracked_vars) {
        add_test("Rollback reverts " + var.name, [var]() {
            return test_transaction_rollback(var);
            });

		add_test("Abort reverts " + var.name, [var]() {
            return test_transaction_abort(var);
			});

        add_test("Commit persists " + var.name, [&]() {
            return test_transaction_commit(var, original_values);
            });

        add_test("Savepoint rollback for " + var.name, [var]() {
            return test_savepoint_rollback(var);
            });

        add_test("Savepoint commit for " + var.name, [&]() {
            return test_savepoint_commit(var, original_values);
            });

		add_test("Rollback and chain for " + var.name, [var]() {
			return test_transaction_rollback_and_chain(var);
			});

        // Multi-value savepoint test
        if (var.test_values.size() > 1) {
           add_test("Multi-value savepoint for " + var.name, [&]() {
                return test_savepoint_release_commit(var, original_values);
                });
        }
    }

    // Add complex scenario tests
    add_test("Nested BEGIN with rollback", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        const auto original_tz = getVariable(conn.get(), "timezone");

        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET timezone = 'UTC'");
        executeQuery(conn.get(), "BEGIN");  // Second BEGIN
        executeQuery(conn.get(), "SET timezone = 'PST8PDT'");
        executeQuery(conn.get(), "ROLLBACK");

        const bool success = getVariable(conn.get(), "timezone") == original_tz;
        return success;
        });

    add_test("Mixed variables in transaction", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        bool success = true;

        executeQuery(conn.get(), "BEGIN");
        for (const auto& [name, var] : tracked_vars) {
            executeQuery(conn.get(), "SET " + var.name + " = " + var.test_values[0]);
        }
        executeQuery(conn.get(), "ROLLBACK");

        for (const auto& [name, var] : tracked_vars) {
            success = (getVariable(conn.get(), var.name) == original_values.at(var.name));
        }
        return success;
        });

    add_test("Mixed variables in transaction (ROLLBACK AND CHAIN)", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        bool success = true;

        executeQuery(conn.get(), "BEGIN");
        for (const auto& [name, var] : tracked_vars) {
            executeQuery(conn.get(), "SET " + var.name + " = " + var.test_values[0]);
        }
        executeQuery(conn.get(), "ROLLBACK AND CHAIN");

        for (const auto& [name, var] : tracked_vars) {
            success = (getVariable(conn.get(), var.name) == original_values.at(var.name));
        }
        return success;
        });

    add_test("Prepared ROLLBACK statement", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);

        executeQuery(conn.get(), "SET client_encoding = 'LATIN1'");
        const auto original = getVariable(conn.get(), "client_encoding");

        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET client_encoding = 'UTF8'");

        {
            diag(">>> Create Prepared Statement [stmt_client_encoding]: ROLLBACK");
            PGResultPtr res(PQprepare(conn.get(), "stmt_client_encoding", "ROLLBACK", 0, NULL), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Prepare failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        bool success = getVariable(conn.get(), "client_encoding") == "UTF8";

        if (!success) {
            diag("client_encoding not set to UTF8 as expected");
            return false;
		}

        {
            diag(">>> Executing Prepared Statement [stmt_client_encoding]: ROLLBACK");
			PGResultPtr res(PQexecPrepared(conn.get(), "stmt_client_encoding", 0, NULL, NULL, NULL, 0), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Execute failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        success = getVariable(conn.get(), "client_encoding") == original;
        if (!success) {
            diag("client_encoding not restored after ROLLBACK");
            return false;
        }

        return success;
	});

    add_test("Prepared ROLLBACK statement 2", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);

        executeQuery(conn.get(), "SET standard_conforming_strings = off");
        const auto original = getVariable(conn.get(), "standard_conforming_strings");

        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET standard_conforming_strings = on");

        {
            diag(">>> Create Prepared Statement [stmt_standard_conforming_strings]: ROLLBACK");
            PGResultPtr res(PQprepare(conn.get(), "stmt_standard_conforming_strings", "ROLLBACK", 0, NULL), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Prepare failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        bool success = getVariable(conn.get(), "standard_conforming_strings") == "on";

        if (!success) {
            diag("standard_conforming_strings not set to 'on' as expected");
            return false;
        }

        {
            diag(">>> Executing Prepared Statement [stmt_standard_conforming_strings]: ROLLBACK");
            PGResultPtr res(PQexecPrepared(conn.get(), "stmt_standard_conforming_strings", 0, NULL, NULL, NULL, 0), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Execute failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        success = getVariable(conn.get(), "standard_conforming_strings") == original;
        if (!success) {
            diag("standard_conforming_strings not restored after ROLLBACK");
            return false;
        }

        return success;
        });

    add_test("Prepared ROLLBACK TO SAVEPOINT statement", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        const auto original = getVariable(conn.get(), "client_encoding");

        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET client_encoding = 'UTF8'");
        executeQuery(conn.get(), "SAVEPOINT sp1");
        executeQuery(conn.get(), "SET client_encoding = 'LATIN1'");

        {
			diag(">>> Create Prepared Statement [stmt_rollback_sp]: ROLLBACK TO SAVEPOINT sp1");
            PGResultPtr res(PQprepare(conn.get(), "stmt_rollback_sp", "ROLLBACK TO SAVEPOINT sp1", 0, NULL), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Prepare failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        // Before executing prepared rollback, client_encoding should be 'LATIN1'
        bool success = getVariable(conn.get(), "client_encoding") == "LATIN1";
        if (!success) {
            diag("client_encoding not changed to 'LATIN1' before rollback");
            return false;
        }

        {
			diag(">>> Executing Prepared Statement [stmt_rollback_sp]: ROLLBACK TO SAVEPOINT sp1");
            PGResultPtr res(PQexecPrepared(conn.get(), "stmt_rollback_sp", 0, NULL, NULL, NULL, 0), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Execute failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        success = getVariable(conn.get(), "client_encoding") == original;
        if (!success) {
            diag("client_encoding not restored after ROLLBACK TO SAVEPOINT");
            return false;
        }

        return true;
        });
    
    add_test("Prepared ROLLBACK TO SAVEPOINT statement 2", [&]() {
        auto conn = createNewConnection(ConnType::BACKEND, "", false);
        const auto original = getVariable(conn.get(), "standard_conforming_strings");

        executeQuery(conn.get(), "BEGIN");
        executeQuery(conn.get(), "SET standard_conforming_strings = on");
        executeQuery(conn.get(), "SAVEPOINT sp1");
        executeQuery(conn.get(), "SET standard_conforming_strings = off");

        {
            diag(">>> Create Prepared Statement [stmt_rollback_sp2]: ROLLBACK TO SAVEPOINT sp1");
            PGResultPtr res(PQprepare(conn.get(), "stmt_rollback_sp2", "ROLLBACK TO SAVEPOINT sp1", 0, NULL), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Prepare failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        // Before executing prepared rollback, client_encoding should be 'off'
        bool success = getVariable(conn.get(), "standard_conforming_strings") == "off";
        if (!success) {
            diag("standard_conforming_strings not changed to 'off' before rollback");
            return false;
        }

        {
            diag(">>> Executing Prepared Statement [stmt_rollback_sp2]: ROLLBACK TO SAVEPOINT sp1");
            PGResultPtr res(PQexecPrepared(conn.get(), "stmt_rollback_sp2", 0, NULL, NULL, NULL, 0), &PQclear);
            if (PQresultStatus(res.get()) != PGRES_COMMAND_OK) {
                diag("Execute failed: %s", PQerrorMessage(conn.get()));
                return false;
            }
        }

        success = getVariable(conn.get(), "standard_conforming_strings") == original;
        if (!success) {
            diag("standard_conforming_strings not restored after ROLLBACK TO SAVEPOINT");
            return false;
        }
   
        return true;
        });

    int total_tests = 0;

    total_tests = tests.size();
    plan(total_tests);

    run_tests();
   
    return exit_status();
}