Combat engine §1 (the other half): a cleric can heal a friend at camp

`--target @user` has been advertised by !help and swallowed by the parser since
SP2 — "reserved for SP3, accept and ignore". §1 wired ally heals inside a fight;
out of combat the cleric still could not put a hit point on anybody but himself,
which is most of where a party is actually hurt: between the rooms, not in them.

The target set is the expedition, not the world. In a fight splitCastTarget
resolves against the people in the fight; the standing-around equivalent is the
people you are travelling with, so both `!cast` paths answer the same question.

Only a heal may name somebody else. UTILITY resolves on the caster and everything
else queues as a PendingCast for the *caster's* next fight, where an ally target
has nothing to mean — so a target on those is refused outright rather than
silently dropped, which is exactly what the old parse did.

The ally's row is mutated with one guarded UPDATE inside a transaction, not a
read-modify-write under a second lock (gifting sets the precedent). Two clerics
healing each other at the same instant would otherwise take their advUserLocks in
opposite orders and deadlock the pair of them. The max-HP clamp lives in the SQL
for the same reason.

Refunds the slot on every path that heals nobody — full-HP ally, downed ally, no
sheet, stranger. A slot spent for zero HP is the kind of thing players do not
forgive. All four are pinned end-to-end through the real handler.

A heal is still not a resurrection: it will not raise the dead, same rule the
combat path holds.

Claude-Session: https://claude.ai/code/session_01J5SQZWoLmL3M3mw2XmHHdy

internal/plugin/dnd_cast.go

@@ -1,7 +1,9 @@
 package plugin
 
 import (
+	"database/sql"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log/slog"
 	"math/rand/v2"
@@ -27,9 +29,11 @@ import (
 //   - Reaction spells (Shield, Counterspell, Absorb Elements) refuse with
 //     a "Phase 11" note — they require the boss turn-based engine.
 //
-// Cross-player targeting (--target @user) is deliberately deferred. SP2
-// supports self-target only. Heals on self work; ally buffs queue with the
-// caster as the target until SP3 wires up the multi-player resolution.
+// Cross-player targeting (`--target @user`, or a trailing `@user`) heals a human
+// on your expedition — see dnd_cast_target.go. Only heals may name somebody else
+// out of combat: UTILITY resolves on the caster, and everything else queues as a
+// PendingCast for the *caster's* next fight, where an ally target has nothing to
+// mean. In-combat targeting is splitCastTarget (combat_cmd.go).
 
 // PendingCast is the shape stored in dnd_character.pending_cast (JSON blob).
 // Keep this minimal — the combat layer resolves the actual numbers on fire.
@@ -97,6 +101,13 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 		return p.dndCastDrop(ctx, c)
 	}
 
+	// An ally target — `--target @alex`, or a trailing `@alex` — comes off the
+	// string before the spell parser sees it, exactly as in combat. It is
+	// resolved (and refused) further down, once we know the spell is a heal: a
+	// target on anything else is a mistake, and refusing it early would cost us
+	// the "which spell?" half of the error message.
+	args, targetName := splitOutOfCombatTarget(args)
+
 	// Parse spell name + optional --upcast N.
 	tokens := strings.Fields(args)
 	upcast := 0
@@ -111,11 +122,6 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 				}
 				i++
 			}
-		case "--target":
-			// Reserved for SP3 — accept and ignore for now.
-			if i+1 < len(tokens) {
-				i++
-			}
 		default:
 			spellTokens = append(spellTokens, tokens[i])
 		}
@@ -195,6 +201,23 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 		}
 	}
 
+	// Resolve an ally target now — BEFORE anything is spent. Out of combat only a
+	// heal can land on somebody else: UTILITY resolves on the caster and
+	// everything else queues as a PendingCast for *this* caster's next fight, so
+	// a target on those would be accepted and then silently dropped.
+	var targetUser id.UserID
+	if targetName != "" {
+		if spell.Effect != EffectSpellHeal {
+			return p.SendDM(ctx.Sender, fmt.Sprintf(
+				"%s isn't a healing spell — outside a fight you can only cast those on someone else. Drop the target to cast it on yourself.", spell.Name))
+		}
+		uid, errMsg := resolveCastTargetOnExpedition(ctx.Sender, targetName)
+		if errMsg != "" {
+			return p.SendDM(ctx.Sender, errMsg)
+		}
+		targetUser = uid // empty when they named themselves — self-heal as usual
+	}
+
 	// Material cost (Revivify, Raise Dead).
 	if spell.MaterialCost > 0 {
 		if p.euro == nil || !p.euro.Debit(ctx.Sender, float64(spell.MaterialCost), "dnd_spell_component") {
@@ -220,6 +243,9 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 	// debited above; if SaveDnDCharacter fails we refund.
 	switch spell.Effect {
 	case EffectSpellHeal:
+		if targetUser != "" {
+			return p.resolveAllyHealOutOfCombat(ctx, c, targetUser, spell, slotLevel)
+		}
 		return p.resolveHealOutOfCombat(ctx, c, spell, slotLevel)
 	case EffectUtility:
 		return p.resolveUtility(ctx, c, spell, slotLevel)
@@ -231,7 +257,10 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 
 // ── Out-of-combat: HEAL ──────────────────────────────────────────────────────
 
-func (p *AdventurePlugin) resolveHealOutOfCombat(ctx MessageContext, c *DnDCharacter, spell SpellDefinition, slotLevel int) error {
+// rollOutOfCombatHeal is what the spell is worth in the caster's hands. It is a
+// property of the caster (their WIS, their domain), never of the body it lands
+// on, so an ally heal rolls exactly the same as a self-heal.
+func rollOutOfCombatHeal(c *DnDCharacter, spell SpellDefinition, slotLevel int) int {
 	dice, faces, _ := parseDamageDice(spell.DamageDice)
 	if dice == 0 {
 		dice, faces = 1, 8 // safety fallback
@@ -253,6 +282,11 @@ func (p *AdventurePlugin) resolveHealOutOfCombat(ctx MessageContext, c *DnDChara
 	}
 	heal += abilityModifier(c.WIS)
 	heal += lifeDomainHealBonus(c, spell, slotLevel)
+	return heal
+}
+
+func (p *AdventurePlugin) resolveHealOutOfCombat(ctx MessageContext, c *DnDCharacter, spell SpellDefinition, slotLevel int) error {
+	heal := rollOutOfCombatHeal(c, spell, slotLevel)
 
 	before := c.HPCurrent
 	c.HPCurrent = min(c.HPMax, c.HPCurrent+heal)
@@ -272,6 +306,51 @@ func (p *AdventurePlugin) resolveHealOutOfCombat(ctx MessageContext, c *DnDChara
 		renderSlotsBrief(ctx.Sender)))
 }
 
+// resolveAllyHealOutOfCombat puts the heal on somebody else's sheet. The slot is
+// already spent, so every failure below refunds it: a heal that lands on nobody
+// must not cost the caster anything.
+func (p *AdventurePlugin) resolveAllyHealOutOfCombat(ctx MessageContext, c *DnDCharacter, target id.UserID, spell SpellDefinition, slotLevel int) error {
+	refund := func(msg string) error {
+		if spell.Level > 0 {
+			_ = refundSpellSlot(ctx.Sender, slotLevel)
+		}
+		return p.SendDM(ctx.Sender, msg)
+	}
+
+	heal := rollOutOfCombatHeal(c, spell, slotLevel)
+	before, after, maxHP, err := healPartyMember(target, heal)
+
+	targetName := charName(target)
+	if targetName == "" {
+		targetName = target.Localpart()
+	}
+	casterName := charName(ctx.Sender)
+	if casterName == "" {
+		casterName = ctx.Sender.Localpart()
+	}
+
+	switch {
+	case errors.Is(err, errHealTargetFull):
+		return refund(fmt.Sprintf("**%s** is already at full health (%d/%d). Slot kept.", targetName, before, maxHP))
+	case errors.Is(err, errHealTargetDown):
+		// The same rule the combat path holds: a heal is not a resurrection.
+		return refund(fmt.Sprintf("**%s** is down — a heal won't bring them back. Slot kept.", targetName))
+	case errors.Is(err, sql.ErrNoRows):
+		return refund(fmt.Sprintf("**%s** hasn't run `!setup` yet, so there's no sheet to heal.", targetName))
+	case err != nil:
+		return refund("Couldn't apply the heal: " + err.Error())
+	}
+
+	_ = p.SendDM(target, fmt.Sprintf(
+		"🩹 **%s** casts **%s** on you — %d HP back (%d → %d / %d).",
+		casterName, spell.Name, after-before, before, after, maxHP))
+
+	return p.SendDM(ctx.Sender, fmt.Sprintf(
+		"🩹 **%s** on **%s** — restored %d HP (%d → %d / %d). %s",
+		spell.Name, targetName, after-before, before, after, maxHP,
+		renderSlotsBrief(ctx.Sender)))
+}
+
 // ── Out-of-combat: UTILITY ──────────────────────────────────────────────────
 
 func (p *AdventurePlugin) resolveUtility(ctx MessageContext, c *DnDCharacter, spell SpellDefinition, slotLevel int) error {
@@ -676,6 +755,7 @@ func renderCastHelp(c *DnDCharacter) string {
 	var b strings.Builder
 	b.WriteString("**Cast a spell**\n\n")
 	b.WriteString("Usage: `!cast <spell> [--upcast N]`\n")
+	b.WriteString("       `!cast <heal> @friend` to heal someone on your expedition.\n")
 	b.WriteString("       `!cast --drop` to clear queued/concentration.\n\n")
 	b.WriteString("Run `!spells` for your full list.\n\n")
 	if pc, ok := decodePendingCast(c.PendingCast); ok {