#include <sourcemod>
#include <sdktools>
#include <Couch>

#pragma semicolon 1
#pragma newdecls required

// How often expired names are swept off the list. Only resends if a name actually dropped.
#define HUD_EXPIRE_INTERVAL 0.25

// Longer names are cut so one can't eat the whole message.
#define HUD_NAME_BYTES 20

// A user message holds 255 bytes; HudMsg's fixed fields take 34 and the string its terminator.
// Overflowing drops the whole message.
#define HUD_MSG_BYTES 255
#define HUD_MSG_HEADER_BYTES 34
#define HUD_TEXT_MAX (HUD_MSG_BYTES - HUD_MSG_HEADER_BYTES - 1)

ConVar g_cvEnabled;
ConVar g_cvTime;

Handle g_hHudSync;
Handle g_hExpireTimer;

float g_fExpire[MAXPLAYERS + 1];	// GetGameTime() at which this client drops off the list.
float g_fLastHit[MAXPLAYERS + 1];	// Ordering key: the most recent shooter is listed first.

float g_fNextExpiry;	// Soonest expiry among the names currently on screen.
bool g_bFlushQueued;	// A send is already scheduled for the next frame.
bool g_bHudShown;		// Clients currently have text up, so an empty list must clear it.

char g_sHudText[HUD_TEXT_MAX + 1];

public Plugin myinfo =
{
	name = "Couch HUD",
	author = "marisakirisame.net",
	description = "Shows who is shooting the couch",
	version = "2.0",
	url = "https://marisakirisame.net"
};

public void OnPluginStart()
{
	g_hHudSync = CreateHudSynchronizer();

	g_cvEnabled = CreateConVar("sm_couch_hud_enabled", "1", "Show the list of players shooting the couch.", FCVAR_NOTIFY, true, 0.0, true, 1.0);
	g_cvTime = CreateConVar("sm_couch_hud_time", "0.5", "How long a player stays on the list after their last hit, in seconds.", FCVAR_NOTIFY, true, 0.5, true, 30.0);

	g_cvEnabled.AddChangeHook(OnEnabledChanged);

	AutoExecConfig(true, "CouchHud");
}

public void OnMapStart()
{
	// TIMER_FLAG_NO_MAPCHANGE already killed the timer.
	g_hExpireTimer = null;
	g_bFlushQueued = false;
	g_bHudShown = false;
	g_fNextExpiry = 0.0;

	for (int i = 1; i <= MAXPLAYERS; i++)
	{
		g_fExpire[i] = 0.0;
		g_fLastHit[i] = 0.0;
	}
}

public void OnClientPutInServer(int client)
{
	g_fExpire[client] = 0.0;
	g_fLastHit[client] = 0.0;
}

public void OnClientDisconnect(int client)
{
	bool bListed = (g_fExpire[client] > GetGameTime());

	g_fExpire[client] = 0.0;
	g_fLastHit[client] = 0.0;

	if (bListed)
		QueueFlush();
}

public void OnEnabledChanged(ConVar convar, const char[] oldValue, const char[] newValue)
{
	if (!convar.BoolValue)
		ResetAll();
}

public void OnLibraryRemoved(const char[] name)
{
	if (StrEqual(name, "Couch"))
		ResetAll();
}

// ---------------------------------------------------------------------------------------------
// Couch forwards
// ---------------------------------------------------------------------------------------------

public void Couch_OnCouchDamaged(int couch, int attacker, float damage)
{
	if (!g_cvEnabled.BoolValue)
		return;

	float fNow = GetGameTime();
	g_fLastHit[attacker] = fNow;
	g_fExpire[attacker] = fNow + g_cvTime.FloatValue;

	QueueFlush();
}

public void Couch_OnCouchRemoved()
{
	ResetAll();
}

// ---------------------------------------------------------------------------------------------
// Sending
// ---------------------------------------------------------------------------------------------

// Once per frame: every hit in a frame (all shotgun pellets, several shooters) lands here, but
// only the first schedules a send.
void QueueFlush()
{
	if (g_bFlushQueued)
		return;

	g_bFlushQueued = true;
	RequestFrame(Frame_Flush);
}

void Frame_Flush(any data)
{
	g_bFlushQueued = false;
	Flush();
}

void Flush()
{
	if (!g_cvEnabled.BoolValue || Couch_GetCouch() == -1)
	{
		ResetAll();
		return;
	}

	if (BuildHudText(g_sHudText, sizeof(g_sHudText)) == 0)
	{
		ClearAll();
		return;
	}

	Send();
}

void Send()
{
	// Hold time matches the listing time, so the text leaves on its own if no update ever comes.
	SetHudTextParams(0.8, 0.2, g_cvTime.FloatValue, 255, 255, 255, 255, 0, 0.0, 0.0, 0.0);

	for (int i = 1; i <= MaxClients; i++)
	{
		if (IsClientInGame(i) && !IsFakeClient(i))
			ShowSyncHudText(i, g_hHudSync, "%s", g_sHudText);
	}

	g_bHudShown = true;

	// Started here rather than from the hit, so a tick between hit and send can't stop the timer.
	if (g_hExpireTimer == null)
		g_hExpireTimer = CreateTimer(HUD_EXPIRE_INTERVAL, Timer_Expire, _, TIMER_REPEAT | TIMER_FLAG_NO_MAPCHANGE);
}

// Most recent shooters first. Returns how many players are listed, shown or not. Names are
// packed until the message is full, then come off the bottom until a "+ N" line fits.
int BuildHudText(char[] text, int maxlen)
{
	float fNow = GetGameTime();
	bool bTaken[MAXPLAYERS + 1];
	int order[MAXPLAYERS + 1];
	int total = 0;

	g_fNextExpiry = 0.0;

	// Selection sort, most recent hit first. The soonest expiry is tracked over everyone listed,
	// since a hidden player lapsing still changes the "+ N" count.
	for (;;)
	{
		int best = 0;

		for (int i = 1; i <= MaxClients; i++)
		{
			if (bTaken[i] || g_fExpire[i] <= fNow || !IsClientInGame(i))
				continue;

			if (best == 0 || g_fLastHit[i] > g_fLastHit[best])
				best = i;
		}

		if (best == 0)
			break;

		bTaken[best] = true;
		order[total++] = best;

		if (g_fNextExpiry == 0.0 || g_fExpire[best] < g_fNextExpiry)
			g_fNextExpiry = g_fExpire[best];
	}

	if (total == 0)
	{
		text[0] = '\0';
		return 0;
	}

	strcopy(text, maxlen, "Shooting couch:");

	// rowStart[n] is the text length before row n, so a row can be cut back off.
	int rowStart[MAXPLAYERS + 1];
	int rows = 0;

	for (; rows < total; rows++)
	{
		char sName[MAX_NAME_LENGTH];
		GetClientName(order[rows], sName, sizeof(sName));
		TruncateUtf8(sName, HUD_NAME_BYTES);

		char sLine[HUD_NAME_BYTES + 2];
		FormatEx(sLine, sizeof(sLine), "\n%s", sName);

		int len = strlen(text);
		if (len + strlen(sLine) >= maxlen)
			break;

		rowStart[rows] = len;
		StrCat(text, maxlen, sLine);
	}

	// Overflow line. A longer count can need another byte, so the fit is rechecked after every drop.
	while (rows < total)
	{
		char sLine[16];
		FormatEx(sLine, sizeof(sLine), "\n+ %d", total - rows);

		if (strlen(text) + strlen(sLine) < maxlen)
		{
			StrCat(text, maxlen, sLine);
			break;
		}

		rows--;
		text[rowStart[rows]] = '\0';
	}

	return total;
}

// Cuts to at most maxBytes without leaving a partial multi-byte character on the end.
void TruncateUtf8(char[] text, int maxBytes)
{
	if (strlen(text) <= maxBytes)
		return;

	int cut = maxBytes;

	// Back up over continuation bytes so the whole character is dropped.
	while (cut > 0 && (text[cut] & 0xC0) == 0x80)
		cut--;

	text[cut] = '\0';
}

public Action Timer_Expire(Handle timer)
{
	if (!g_bHudShown)
	{
		g_hExpireTimer = null;
		return Plugin_Stop;
	}

	// Only resend when a name has lapsed.
	if (GetGameTime() >= g_fNextExpiry)
		Flush();

	return Plugin_Continue;
}

void ClearAll()
{
	if (!g_bHudShown)
		return;

	for (int i = 1; i <= MaxClients; i++)
	{
		if (IsClientInGame(i) && !IsFakeClient(i))
			ClearSyncHud(i, g_hHudSync);
	}

	g_bHudShown = false;
}

// The expiry timer sees g_bHudShown clear on its next tick and stops itself, so this is safe
// to call from inside it.
void ResetAll()
{
	for (int i = 1; i <= MAXPLAYERS; i++)
	{
		g_fExpire[i] = 0.0;
		g_fLastHit[i] = 0.0;
	}

	ClearAll();
}