/// Dealing with results of queries
module dpq2.result;

public import dpq2.conv.to_d_types;
public import dpq2.conv.to_bson;
public import dpq2.oids;
public import dpq2.value;

import dpq2.connection: Connection;
import dpq2.args: QueryParams;
import dpq2.exception;
import derelict.pq.pq;

import core.vararg;
import std.string: toStringz;
import std.exception: enforce, assertThrown;
import core.exception: OutOfMemoryError;
import std.bitmanip: bigEndianToNative;
import std.conv: to;

/// Result table's cell coordinates
private struct Coords
{
    size_t row; /// Row
    size_t col; /// Column
}

package immutable final class ResultContainer
{
    // ResultContainer allows only one copy of PGresult* due to avoid double free.
    // For the same reason this class is declared as final.
    private PGresult* result;
    alias result this;

    nothrow invariant()
    {
        assert( result != null );
    }

    package this(immutable PGresult* r)
    {
        assert(r);

        result = r;
    }

    ~this()
    {
        assert(result != null);

        PQclear(result);
    }
}

/// Contains result of query regardless of whether it contains an error or data answer
immutable class Result
{
    private ResultContainer result;

    package this(immutable ResultContainer r)
    {
        result = r;
    }

    /// Returns the result status of the command.
    ExecStatusType status() nothrow
    {
        return PQresultStatus(result);
    }

    /// Text description of result status.
    string statusString()
    {
        return PQresStatus(status).to!string;
    }

    /// Returns the error message associated with the command, or an empty string if there was no error.
    string resultErrorMessage()
    {
        return PQresultErrorMessage(result).to!string;
    }

    /// Returns an individual field of an error report.
    string resultErrorField(int fieldcode)
    {
        return PQresultErrorField(result, fieldcode).to!string;
    }

    /// Creates Answer object
    immutable(Answer) getAnswer()
    {
        return new immutable Answer(result);
    }

    ///
    string toString()
    {
        import std.ascii: newline;

        string err = resultErrorMessage();

        return statusString()~(err.length != 0 ? newline~err : "");
    }
}

/// Contains result of query with valid data answer
immutable class Answer : Result
{
    package this(immutable ResultContainer r)
    {
        super(r);

        checkAnswerForErrors();
    }

    private void checkAnswerForErrors()
    {
        switch(status)
        {
            case PGRES_COMMAND_OK:
            case PGRES_TUPLES_OK:
            case PGRES_SINGLE_TUPLE:
            case PGRES_COPY_IN:
                break;

            case PGRES_COPY_OUT:
                throw new AnswerException(ExceptionType.COPY_OUT_NOT_IMPLEMENTED, "COPY TO not yet supported");

            default:
                throw new ResponseException(this, __FILE__, __LINE__);
        }
    }

    /**
     * Returns the command status tag from the SQL command that generated the PGresult
     * Commonly this is just the name of the command, but it might include
     * additional data such as the number of rows processed.
     */
    string cmdStatus()
    {
        return (cast(PGresult*) result.result).PQcmdStatus.to!string;
    }

    /**
     * Returns the number of rows affected by the SQL command.
     * This function returns a string containing the number of rows affected by the SQL statement
     * that generated the Answer. This function can only be used following the execution of
     * a SELECT, CREATE TABLE AS, INSERT, UPDATE, DELETE, MOVE, FETCH, or COPY statement,
     * or an EXECUTE of a prepared query that contains an INSERT, UPDATE, or DELETE statement.
     * If the command that generated the Anwser was anything else, cmdTuples returns an empty string.
    */
    string cmdTuples()
    {
        return PQcmdTuples(cast(PGresult*) result.result).to!string;
    }

    /// Returns row count
    size_t length() nothrow { return PQntuples(result); }

    /// Returns column count
    size_t columnCount() nothrow { return PQnfields(result); }

    /// Returns column format
    ValueFormat columnFormat( const size_t colNum )
    {
        assertCol( colNum );

        return cast(ValueFormat) PQfformat(result, to!int(colNum));
    }

    /// Returns column Oid
    OidType OID( size_t colNum )
    {
        assertCol( colNum );

        return PQftype(result, to!int(colNum)).oid2oidType;
    }

    /// Checks if column type is array
    bool isArray( const size_t colNum )
    {
        assertCol(colNum);

        return dpq2.oids.isSupportedArray(OID(colNum));
    }
    alias isSupportedArray = isArray; //TODO: deprecated

    /// Returns column number by field name
    size_t columnNum( string columnName )
    {
        import std.internal.cstring : tempCString;
        size_t n = ( string v, immutable(PGresult*) r ) @trusted {
            auto tmpstr = v.tempCString; // freed at the end of the scope, also uses SSO
            return PQfnumber(r, tmpstr);
        } ( columnName, result );

        if( n == -1 )
            throw new AnswerException(ExceptionType.COLUMN_NOT_FOUND,
                    "Column '"~columnName~"' is not found", __FILE__, __LINE__);

        return n;
    }

    /// Returns column name by field number
    string columnName( in size_t colNum )
    {
        const char* s = PQfname(result, colNum.to!int);

        if( s == null )
            throw new AnswerException(
                    ExceptionType.OUT_OF_RANGE,
                    "Column "~to!string(colNum)~" is out of range 0.."~to!string(columnCount),
                    __FILE__, __LINE__
                );

        return s.to!string;
    }

    /// Returns true if the column exists, false if not
    bool columnExists( string columnName )
    {
        size_t n = PQfnumber(result, columnName.toStringz);

        return n != -1;
    }

    /// Returns row of cells
    immutable (Row) opIndex(in size_t row)
    {
        return immutable Row(this, row);
    }

    /**
     Returns the number of parameters of a prepared statement.
     This function is only useful when inspecting the result of describePrepared.
     For other types of queries it will return zero.
    */
    uint nParams()
    {
        return PQnparams(result);
    }

    /**
     Returns the data type of the indicated statement parameter.
     Parameter numbers start at 0.
     This function is only useful when inspecting the result of describePrepared.
     For other types of queries it will return zero.
    */
    OidType paramType(T)(T paramNum)
    {
        return PQparamtype(result, paramNum.to!uint).oid2oidType;
    }

    ///
    override string toString()
    {
        import std.ascii: newline;

        string res;

        foreach(n; 0 .. columnCount)
            res ~= columnName(n)~"::"~OID(n).to!string~"\t";

        res ~= newline;

        foreach(row; rangify(this))
            res ~= row.toString~newline;

        return super.toString~newline~res;
    }

    private void assertCol( const size_t c )
    {
        if(!(c < columnCount))
            throw new AnswerException(
                ExceptionType.OUT_OF_RANGE,
                "Column "~to!string(c)~" is out of range 0.."~to!string(columnCount)~" of result columns",
                __FILE__, __LINE__
            );
    }

    private void assertRow( const size_t r )
    {
        if(!(r < length))
            throw new AnswerException(
                ExceptionType.OUT_OF_RANGE,
                "Row "~to!string(r)~" is out of range 0.."~to!string(length)~" of result rows",
                __FILE__, __LINE__
            );
    }

     private void assertCoords( const Coords c )
    {
        assertRow( c.row );
        assertCol( c.col );
    }
}

/// Creates forward range from immutable Answer
auto rangify(T)(T obj)
{
    struct Rangify(T)
    {
        T obj;
        alias obj this;

        private int curr;

        this(T o)
        {
            obj = o;
        }

        auto front(){ return obj[curr]; }
        void popFront(){ ++curr; }
        bool empty(){ return curr >= obj.length; }
    }

    return Rangify!(T)(obj);
}

/// Represents one row from the answer table
immutable struct Row
{
    private Answer answer;
    private size_t row;

    ///
    this(immutable Answer answer, in size_t row)
    {
        answer.assertRow( row );

        this.answer = answer;
        this.row = row;
    }

    /// Returns the actual length of a cell value in bytes.
    size_t size( const size_t col )
    {
        answer.assertCol(col);

        return PQgetlength(answer.result, to!int(row), to!int(col));
    }

    /// Checks if value is NULL
    ///
    /// Do not confuse it with Nullable's isNull method
    bool isNULL( const size_t col )
    {
        answer.assertCol(col);

        return PQgetisnull(answer.result, to!int(row), to!int(col)) != 0;
    }

    /// Checks if column with name exists
    bool columnExists(in string column)
    {
        return answer.columnExists(column);
    }

    /// Returns cell value by column number
    immutable (Value) opIndex(in size_t col)
    {
        answer.assertCoords( Coords( row, col ) );

        // The pointer returned by PQgetvalue points to storage that is part of the PGresult structure.
        // One should not modify the data it points to, and one must explicitly copy the data into other
        // storage if it is to be used past the lifetime of the PGresult structure itself.
        immutable ubyte* v = cast(immutable) PQgetvalue(answer.result, to!int(row), to!int(col));
        size_t s = size(col);

        return immutable Value(v[0..s], answer.OID(col), isNULL(col), answer.columnFormat(col));
    }

    /// Returns cell value by field name
    immutable (Value) opIndex(in string column)
    {
        return opIndex(columnNum(column));
    }

    /// Returns column number by field name
    size_t columnNum( string columnName )
    {
        return answer.columnNum( columnName );
    }

    /// Returns column name by field number
    string columnName( in size_t colNum )
    {
        return answer.columnName( colNum );
    }

    /// Returns column count
    size_t length() { return answer.columnCount(); }

    ///
    string toString()
    {
        string res;

        foreach(val; rangify(this))
        {
            try
                res ~= dpq2.result.toString(val);
            catch(ValueConvException e)
                res ~= `#%???%#`;

            res ~= "\t";
        }

        return res;
    }
}

/// Creates Array from appropriate Value
immutable (Array) asArray(immutable(Value) v)
{
    if(v.format == ValueFormat.TEXT)
        throw new ValueConvException(ConvExceptionType.NOT_ARRAY,
            "Value internal format is text",
            __FILE__, __LINE__
        );

    if(!v.isSupportedArray)
        throw new ValueConvException(ConvExceptionType.NOT_ARRAY,
            "Format of the value is "~to!string(v.oidType)~", isn't supported array",
            __FILE__, __LINE__
        );

    return immutable Array(v);
}

///
string toString(immutable Value v)
{
    import vibe.data.bson: Bson;

    return v.isNull ? "NULL" : v.as!Bson.toString;
}

package struct ArrayHeader_net // network byte order
{
    ubyte[4] ndims; // number of dimensions of the array
    ubyte[4] dataoffset_ign; // offset for data, removed by libpq. may be it contains isNULL flag!
    ubyte[4] OID; // element type OID
}

package struct Dim_net // network byte order
{
    ubyte[4] dim_size; // number of elements in dimension
    ubyte[4] lbound; // unknown
}

private @safe struct BytesReader(A = const ubyte[])
{
    A arr;
    size_t currIdx;

    this(A a)
    {
        arr = a;
    }

    T* read(T)() @trusted
    {
        const incremented = currIdx + T.sizeof;

        // Malformed buffer?
        if(incremented > arr.length)
            throw new AnswerException(ExceptionType.FATAL_ERROR, null);

        auto ret = cast(T*) &arr[currIdx];

        currIdx = incremented;

        return ret;
    }

    A readBuff(size_t len)
    in(len >= 0)
    {
        const incremented = currIdx + len;

        // Malformed buffer?
        if(incremented > arr.length)
            throw new AnswerException(ExceptionType.FATAL_ERROR, null);

        auto ret = arr[currIdx .. incremented];

        currIdx = incremented;

        return ret;
    }
}

///
struct ArrayProperties
{
    OidType OID = OidType.Undefined; /// Oid
    int[] dimsSize; /// Dimensions sizes info
    size_t nElems; /// Total elements
    package size_t dataOffset;

    this(in Value cell)
    {
        try
            fillStruct(cell);
        catch(AnswerException e)
        {
            // Malformed array bytes buffer?
            if(e.type == ExceptionType.FATAL_ERROR && e.msg is null)
                throw new ValueConvException(
                    ConvExceptionType.CORRUPTED_ARRAY,
                    "Corrupted array",
                    __FILE__, __LINE__, e
                );
            else
                throw e;
        }
    }

    private void fillStruct(in Value cell)
    {
        auto data = BytesReader!(immutable ubyte[])(cell.data);

        const ArrayHeader_net* h = data.read!ArrayHeader_net;
        int nDims = bigEndianToNative!int(h.ndims);
        OID = oid2oidType(bigEndianToNative!Oid(h.OID));

        if(nDims < 0)
            throw new ValueConvException(ConvExceptionType.CORRUPTED_ARRAY,
                "Array dimensions number is negative ("~to!string(nDims)~")",
            );

        dataOffset = ArrayHeader_net.sizeof + Dim_net.sizeof * nDims;

        dimsSize = new int[nDims];

        // Recognize dimensions of array
        for( auto i = 0; i < nDims; ++i )
        {
            Dim_net* d = (cast(Dim_net*) (h + 1)) + i;

            const dim_size = bigEndianToNative!int(d.dim_size);
            const lbound = bigEndianToNative!int(d.lbound);

            if(dim_size < 0)
                throw new ValueConvException(ConvExceptionType.CORRUPTED_ARRAY,
                    "Dimension size is negative ("~to!string(dim_size)~")",
                );

            // FIXME: What is lbound in postgresql array reply?
            if(!(lbound == 1))
                throw new ValueConvException(ConvExceptionType.CORRUPTED_ARRAY,
                    "Please report if you came across this error! lbound=="~to!string(lbound),
                );

            dimsSize[i] = dim_size;

            if(i == 0) // first dimension
                nElems = dim_size;
            else
                nElems *= dim_size;
        }
    }
}

/// Represents Value as array
///
/// Actually it is a reference to the cell value of the answer table
immutable struct Array
{
    ArrayProperties ap; ///
    alias ap this;

    private ubyte[][] elements;
    private bool[] elementIsNULL;

    this(immutable Value cell)
    {
        if(!(cell.format == ValueFormat.BINARY))
            throw new ValueConvException(ConvExceptionType.NOT_BINARY,
                msg_NOT_BINARY, __FILE__, __LINE__);

        ap = cast(immutable) ArrayProperties(cell);

        // Looping through all elements and fill out index of them
        try
        {
            auto elements = new immutable (ubyte)[][ nElems ];
            auto elementIsNULL = new bool[ nElems ];

            auto data = BytesReader!(immutable ubyte[])(cell.data[ap.dataOffset .. $]);

            for(uint i = 0; i < nElems; ++i)
            {
                /// size in network byte order
                const size_net = data.read!(ubyte[int.sizeof]);

                uint size = bigEndianToNative!uint(*size_net);
                if( size == size.max ) // NULL magic number
                {
                    elementIsNULL[i] = true;
                }
                else
                {
                    elementIsNULL[i] = false;
                    elements[i] = data.readBuff(size);
                }
            }

            this.elements = elements.idup;
            this.elementIsNULL = elementIsNULL.idup;
        }
        catch(AnswerException e)
        {
            // Malformed array bytes buffer?
            if(e.type == ExceptionType.FATAL_ERROR && e.msg is null)
                throw new ValueConvException(
                    ConvExceptionType.CORRUPTED_ARRAY,
                    "Corrupted array",
                    __FILE__, __LINE__, e
                );
            else
                throw e;
        }
    }

    /// Returns number of elements in array
    /// Useful for one-dimensional arrays
    size_t length()
    {
        return nElems;
    }

    /// Returns Value struct by index
    /// Useful for one-dimensional arrays
    immutable (Value) opIndex(size_t n)
    {
        return opIndex(n.to!int);
    }

    /// Returns Value struct by index
    /// Useful for one-dimensional arrays
    immutable (Value) opIndex(int n)
    {
        return getValue(n);
    }

    /// Returns Value struct
    /// Useful for multidimensional arrays
    immutable (Value) getValue( ... )
    {
        auto n = coords2Serial( _argptr, _arguments );

        return getValueByFlatIndex(n);
    }

    ///
    package immutable (Value) getValueByFlatIndex(size_t n)
    {
        return immutable Value(elements[n], OID, elementIsNULL[n], ValueFormat.BINARY);
    }

    /// Value NULL checking
    bool isNULL( ... )
    {
        auto n = coords2Serial( _argptr, _arguments );
        return elementIsNULL[n];
    }

    private size_t coords2Serial( va_list _argptr, TypeInfo[] _arguments )
    {
        assert( _arguments.length > 0, "Number of the arguments must be more than 0" );

        // Variadic args parsing
        auto args = new int[ _arguments.length ];

        if(!(dimsSize.length == args.length))
            throw new ValueConvException(
                ConvExceptionType.OUT_OF_RANGE,
                "Mismatched dimensions number in Value and passed arguments: "~dimsSize.length.to!string~" and "~args.length.to!string,
            );

        for( uint i; i < args.length; ++i )
        {
            assert( _arguments[i] == typeid(int) );
            args[i] = va_arg!(int)(_argptr);

            if(!(dimsSize[i] > args[i]))
                throw new ValueConvException(
                    ConvExceptionType.OUT_OF_RANGE,
                    "Index is out of range",
                );
        }

        // Calculates serial number of the element
        auto inner = args.length - 1; // inner dimension
        auto element_num = args[inner]; // serial number of the element
        uint s = 1; // perpendicular to a vector which size is calculated currently
        for( auto i = inner; i > 0; --i )
        {
            s *= dimsSize[i];
            element_num += s * args[i-1];
        }

        assert( element_num <= nElems );
        return element_num;
    }
}

/// Notify
class Notify
{
    private immutable PGnotify* n;

    package this(immutable PGnotify* pgn)
    {
        assert(pgn != null);

        n = pgn;
        cast(void) enforce!OutOfMemoryError(n, "Can't write notify");
    }

    ~this()
    {
        PQfreemem( cast(void*) n );
    }

    /// Returns notification condition name
    string name() { return to!string( n.relname ); }

    /// Returns notification parameter
    string extra() { return to!string( n.extra ); }

    /// Returns process ID of notifying server process
    size_t pid() { return n.be_pid; }
}

/// Covers errors of Answer creation when data was not received due to syntax errors, etc
class ResponseException : Dpq2Exception
{
    immutable(Result) result;
    alias result this;

    this(immutable(Result) result, string file = __FILE__, size_t line = __LINE__)
    {
        this.result = result;

        super(result.resultErrorMessage(), file, line);
    }
}

// TODO: deprecated
alias AnswerCreationException = ResponseException;

/// Answer exception types
enum ExceptionType
{
    FATAL_ERROR, ///
    COLUMN_NOT_FOUND, /// Column is not found
    OUT_OF_RANGE, ///
    COPY_OUT_NOT_IMPLEMENTED = 10000, /// TODO
}

/// Covers errors of access to Answer data
class AnswerException : Dpq2Exception
{
    const ExceptionType type; /// Exception type

    this(ExceptionType t, string msg, string file = __FILE__, size_t line = __LINE__) pure @safe
    {
        type = t;
        super(msg, file, line);
    }
}

package immutable msg_NOT_BINARY = "Format of the column is not binary";

version (integration_tests)
void _integration_test( string connParam )
{
    import core.exception: AssertError;

    auto conn = new Connection(connParam);

    // Text type results testing
    {
        string sql_query =
        "select now() as time,  'abc'::text as field_name,   123,  456.78\n"~
        "union all\n"~

        "select now(),          'def'::text,                 456,  910.11\n"~
        "union all\n"~

        "select NULL,           'ijk_АБВГД'::text,           789,  12345.115345";

        auto e = conn.exec(sql_query);

        assert( e[1][2].as!PGtext == "456" );
        assert( e[2][1].as!PGtext == "ijk_АБВГД" );
        assert( !e[0].isNULL(0) );
        assert( e[2].isNULL(0) );
        assert( e.columnNum( "field_name" ) == 1 );
        assert( e[1]["field_name"].as!PGtext == "def" );
        assert(e.columnExists("field_name"));
        assert(!e.columnExists("foo"));
    }

    // Binary type arguments testing:
    QueryParams p;
    p.resultFormat = ValueFormat.BINARY;
    p.sqlCommand = "SELECT "~
        "-32761::smallint, "~
        "-2147483646::integer as integer_value, "~
        "'first line\nsecond line'::text, "~
        "array[[[1,  2, 3], "~
               "[4,  5, 6]], "~

              "[[7,  8, 9], "~
              "[10, 11,12]], "~

              "[[13,14,NULL], "~
               "[16,17,18]]]::integer[] as test_array, "~
        "NULL::smallint,"~
        "array[11,22,NULL,44]::integer[] as small_array, "~
        "array['1','23',NULL,'789A']::text[] as text_array, "~
        "array[]::text[] as empty_array, "~
        "'2022-02-23'::date as unsupported_toString_output_type";

    auto r = conn.execParams(p);

    {
        assert( r[0].isNULL(4) );
        assert( !r[0].isNULL(2) );

        assert( r.OID(3) == OidType.Int4Array );
        assert( r.isSupportedArray(3) );
        assert( !r.isSupportedArray(2) );
        assert( r[0].columnExists("test_array") );
        auto v = r[0]["test_array"];
        assert( v.isSupportedArray );
        assert( !r[0][2].isSupportedArray );
        auto a = v.asArray;
        assert( a.OID == OidType.Int4 );
        assert( a.getValue(2,1,2).as!PGinteger == 18 );
        assert( a.isNULL(2,0,2) );
        assert( !a.isNULL(2,1,2) );
        assert( r[0]["small_array"].asArray[1].as!PGinteger == 22 );
        assert( r[0]["small_array"].asArray[2].isNull );
        assert( r[0]["text_array"].asArray[2].isNull );
        assert( r.columnName(3) == "test_array" );
        assert( r[0].columnName(3) == "test_array" );
        assert( r[0]["empty_array"].asArray.nElems == 0 );
        assert( r[0]["empty_array"].asArray.dimsSize.length == 0 );
        assert( r[0]["empty_array"].asArray.length == 0 );
        assert( r[0]["text_array"].asArray.length == 4 );
        assert( r[0]["test_array"].asArray.length == 18 );

        r[0].toString; // Must not throw
        assertThrown!ValueConvException(r[0]["unsupported_toString_output_type"].toString);

        // Access to NULL cell
        {
            bool isNullFlag = false;
            try
                cast(void) r[0][4].as!PGsmallint;
            catch(AssertError)
                isNullFlag = true;
            finally
                assert(isNullFlag);
        }

        // Access to NULL array element
        {
            bool isNullFlag = false;
            try
                cast(void) r[0]["small_array"].asArray[2].as!PGinteger;
            catch(AssertError)
                isNullFlag = true;
            finally
                assert(isNullFlag);
        }
    }

    // Notifies test
    {
        conn.exec( "listen test_notify; notify test_notify, 'test payload'" );
        auto notify = conn.getNextNotify;

        assert( notify.name == "test_notify" );
        assert( notify.extra == "test payload" );
    }

    // Async query test 1
    conn.sendQuery( "select 123; select 456; select 789" );
    while( conn.getResult() !is null ){}
    assert( conn.getResult() is null ); // removes null answer at the end

    // Async query test 2
    conn.sendQueryParams(p);
    while( conn.getResult() !is null ){}
    assert( conn.getResult() is null ); // removes null answer at the end

    {
        // Range test
        auto rowsRange = rangify(r);
        size_t count = 0;

        foreach(row; rowsRange)
            foreach(elem; rangify(row))
                count++;

        assert(count == 9);
    }

    {
        bool exceptionFlag = false;

        try r[0]["integer_value"].as!PGtext;
        catch(ValueConvException e)
        {
            exceptionFlag = true;
            assert(e.msg.length > 5); // error message check
        }
        finally
            assert(exceptionFlag);
    }

    {
        bool exceptionFlag = false;

        try conn.exec("WRONG SQL QUERY");
        catch(ResponseException e)
        {
            exceptionFlag = true;
            assert(e.msg.length > 20); // error message check

            version(LDC) destroy(e); // before Derelict unloads its bindings (prevents SIGSEGV)
        }
        finally
            assert(exceptionFlag);
    }

    {
        import dpq2.conv.from_d_types : toValue;

        conn.exec("CREATE TABLE test (num INTEGER)");
        scope (exit) conn.exec("DROP TABLE test");
        conn.prepare("test", "INSERT INTO test (num) VALUES ($1)");
        QueryParams qp;
        qp.preparedStatementName = "test";
        qp.args = new Value[1];
        foreach (i; 0..10)
        {
            qp.args[0] = i.toValue;
            conn.execPrepared(qp);
        }

        auto res = conn.exec("DELETE FROM test");
        assert(res.cmdTuples == "10");
    }
}