const std = @import("std");
const log = std.log.scoped(.pgz);
const SSHashMap = std.StringHashMap([]const u8);
const Config = @import("config.zig");
const proto = @import("../proto/proto.zig");
const StartupMessage = proto.StartupMessage;
const PasswordMessage = proto.PasswordMessage;
const BackendMessage = proto.BackendMessage;
const RowDescription = proto.RowDescription;
const read_message = proto.read_message;
const ProtocolError = @import("../main.zig").ProtocolError;
const ServerError = @import("../main.zig").ServerError;
const ClientError = @import("../main.zig").ClientError;
const diagnosticReader = @import("../main.zig").diagnosticReader;

const Conn = @This();

const ConnStatus = enum {
    connStatusUninitialized,
    connStatusConnecting,
    connStatusClosed,
    connStatusIdle,
    connStatusBusy,
};

allocator: std.mem.Allocator,
stream: std.net.Stream,
config: Config,
status: ConnStatus = .connStatusUninitialized,

pub fn connect(config: Config) !Conn {
    const allocator = config.allocator;
    var stream = switch (config.address) {
        .net => |addr| try std.net.tcpConnectToAddress(addr),
        .unix => |path| try std.net.connectUnixSocket(path),
    };
    var res = Conn{
        .allocator = allocator,
        .stream = stream,
        .config = config,
    };
    errdefer res.deinit();
    var writer = stream.writer();
    var dr = diagnosticReader(100, stream.reader());
    var reader = dr.reader();
    _ = reader;
    var params = SSHashMap.init(allocator);
    try params.put("user", config.user);
    if (config.database) |database| try params.put("database", database);
    var sm = StartupMessage{
        .parameters = params,
    };
    defer sm.deinit(allocator);
    try sm.write(allocator, writer);
    lp: while (true) {
        var anymsg = try res.receive_message();
        defer anymsg.deinit(allocator);
        switch (anymsg) {
            .ReadyForQuery => {
                break :lp;
            },
            .AuthenticationRequest => |ar| {
                switch (ar.inner_type) {
                    .AuthRequestTypeOk => {},
                    .AuthRequestTypeCleartextPassword => {
                        if (config.password) |password| {
                            const pm = PasswordMessage{ .password = password };
                            try pm.write(allocator, writer);
                        } else {
                            return ClientError.NoPasswordSupplied;
                        }
                    },
                }
            },
            else => {
                // deliberately do nothing, we must wait for ready before the connection can be used.
            },
        }
    }
    return res;
}

// Messages should always be received through this function.
// this'll handle generic stuff that should happen on the connection
fn receive_message(self: *Conn) !BackendMessage {
    var anymsg = try read_message(self.allocator, self.stream.reader());
    errdefer anymsg.deinit(self.allocator);
    switch (anymsg) {
        .ReadyForQuery => {
            // TODO handle TxStatus
        },
        .ParameterStatus => {
            // TODO handle parameter status
        },
        .ErrorResponse => |err| {
            if (std.mem.eql(u8, err.severity, "FATAL")) {
                self.status = .connStatusClosed;
                // TODO close the connection here? But it should really be the caller's responsiblilty
                return ServerError.ErrorResponse;
            }
        },
        // .NoticeResponse => {
        //     // TODO handle notice response
        // },
        // .NotificationResponse => {
        //     // TODO handle notificationResponse
        // },
        .BackendKeyData => {
            // TODO handle backend key data
        },
        else => {
            // deliberately do nothing, caller can presumably handle them.
        },
    }
    return anymsg;
}

pub fn deinit(self: *Conn) void {
    self.stream.close();
}

pub const ResultIterator = struct {
    conn: *Conn,
    multi_iterator: ?*MultiResultIterator = null,
    row_description: ?proto.RowDescription = null,
    current_datarow: ?proto.DataRow = null,
    command_complete: ?proto.CommandComplete = null,
    pub fn init(conn: *Conn) ResultIterator {
        return .{
            .conn = conn,
        };
    }
    pub fn deinit(self: *ResultIterator) void {
        if (self.row_description != null) self.row_description.?.deinit(self.conn.allocator);
        if (self.current_datarow != null) self.current_datarow.?.deinit(self.conn.allocator);
        if (self.command_complete != null) self.command_complete.?.deinit(self.conn.allocator);
    }
    // NextRow advances the ResultIterator to the next row and returns a row if one is available.
    // or null if we've reached the end of the reuslt.
    pub fn next_row(self: *ResultIterator) !?[][]const u8 {
        while (self.command_complete == null) {
            var msg = try self.receive_message();
            switch (msg) {
                .DataRow => {
                    return self.current_datarow.?.columns;
                },
                else => {
                    msg.deinit(self.conn.allocator);
                },
            }
        }
        return null;
    }

    pub fn skip_to_end(self: *ResultIterator) !void {
        while (self.command_complete == null) {
            _ = try self.receive_message();
        }
    }

    fn receive_message(self: *ResultIterator) !BackendMessage {
        var msg = if (self.multi_iterator == null) try self.conn.receive_message() else try self.multi_iterator.?.receive_message();
        switch (msg) {
            .DataRow => |dr| {
                if (self.current_datarow != null) self.current_datarow.?.deinit(self.conn.allocator);
                self.current_datarow = try dr.clone(self.conn.allocator);
            },
            .RowDescription => |rd| {
                if (self.row_description != null) return ProtocolError.UnexpectedMessage;
                self.row_description = try rd.clone(self.conn.allocator);
            },
            .CommandComplete => |cc| {
                if (self.command_complete != null) return ProtocolError.UnexpectedMessage;
                self.command_complete = try cc.clone(self.conn.allocator);
            },
        }
        return msg;
    }
};

pub const MultiResultIterator = struct {
    conn: *Conn,
    cri: ?*ResultIterator,

    // returns the next result iterator, or null if we've reached the end of the results
    pub fn next_result(self: *MultiResultIterator) !?*ResultIterator {
        _ = self;
        // if (self.cri != null) {
        //     try self.cri.?.skip_to_end();
        // }
        return error.NotImplemented;
    }

    fn receive_message(self: *MultiResultIterator) !BackendMessage {
        _ = self;
        // var msg = try self.conn.receive_message();
        // switch (msg) {}
        // return msg;
        return error.NotImplemented;
    }
};

// Execute some SQL using postgres' simple query protocol
pub fn exec(self: *Conn, query: []const u8) !ResultIterator {
    const qr = proto.Query{
        .query = query,
    };
    var writer = self.stream.writer();
    try qr.write(self.allocator, writer);
    // TODO multi result iterator since query could contain multiple queries
    return ResultIterator{
        .conn = self,
    };
}

test "connect unix" {
    // must have a local postgres runnning
    // TODO maybe use docker to start one?
    const allocator = std.testing.allocator;
    const cfg = Config{
        .allocator = allocator,
        .address = .{ .unix = "/run/postgresql/.s.PGSQL.5432" },
        .database = "martin",
        .user = "martin",
    };
    var conn = try Conn.connect(cfg);
    defer conn.deinit();
}

test "connect tcp with password" {
    const allocator = std.testing.allocator;
    const cfg = Config{
        .allocator = allocator,
        .address = .{ .net = std.net.Address{ .in = std.net.Ip4Address.init([4]u8{ 127, 0, 0, 1 }, 5432) } },
        .database = "martin",
        .user = "martin",
        .password = "martin",
    };
    var conn = try Conn.connect(cfg);
    defer conn.deinit();
}

test "connect tcp with wrong password" {
    // TODO how to disable failing tests on error log
    // const allocator = std.testing.allocator;
    // const cfg = Config{
    //     .allocator = allocator,
    //     .address = .{ .net = std.net.Address{ .in = std.net.Ip4Address.init([4]u8{ 127, 0, 0, 1 }, 5432) } },
    //     .database = "martin",
    //     .user = "martin",
    //     .password = "foobar",
    // };
    // try std.testing.expectError(ServerError.ErrorResponse, Conn.connect(cfg));
}