package plugin

import (
	"fmt"
	"log/slog"

	"maunium.net/go/mautrix/id"
)

// Phase 13 — Combatant reconstruction for turn-based fights.
//
// The auto-resolve path (runZoneCombat) builds a player/enemy Combatant pair,
// runs SimulateCombat, and discards them. The turn-based path needs the same
// pair, but rebuilt fresh on every player command from persisted session
// state — so the build is extracted here as buildZoneCombatants, and
// combatantsForSession wraps it for the resume case.
//
// HP is deliberately NOT carried by the Combatant pair: the turn engine reads
// live HP from the CombatSession row (sess.PlayerHP / sess.EnemyHP), so the
// rebuilt Combatants only need correct Stats/Mods/Ability. Re-deriving from
// current character state each round is safe because zone equipment, streaks,
// and bonuses don't change mid-fight.
//
// applyPendingCast and the auto-heal consumable setup are intentionally left
// out of the shared builder — those are one-shot mutations that runZoneCombat
// applies once before SimulateCombat. Re-applying them on every turn-based
// round would double-consume. Mid-fight !cast / !consume buffs are instead
// persisted on the CombatSession and folded back in by combatantsForSession
// via applySessionBuffs.

// buildZoneCombatants derives the player/enemy Combatant pair for a zone
// encounter: the player's full D&D layer (stats + class/race/subclass passives
// + armed ability) and the monster's bestiary stat block with tier scaling and
// the DM-mood combat tilt folded in. The returned dndChar is handed back so
// callers can run post-combat subclass persistence without reloading it.
func (p *AdventurePlugin) buildZoneCombatants(
	userID id.UserID,
	monster DnDMonsterTemplate,
	tier int,
	dmMood int,
) (player Combatant, enemy Combatant, dndChar *DnDCharacter, err error) {
	tilt := dmMoodCombatTilt(dmMood)
	char, err := loadAdvCharacter(userID)
	if err != nil || char == nil {
		return Combatant{}, Combatant{}, nil, fmt.Errorf("load adv character: %w", err)
	}
	equip, err := loadAdvEquipment(userID)
	if err != nil {
		return Combatant{}, Combatant{}, nil, fmt.Errorf("load equipment: %w", err)
	}
	bonuses := p.loadCombatBonuses(userID, char)
	chatLvl := p.chatLevel(userID)

	playerStats, playerMods := DerivePlayerStats(char, equip, bonuses, chatLvl, char.CurrentStreak, false)

	dndChar, _, err = ensureDnDCharacterForCombat(userID, char)
	if err != nil {
		return Combatant{}, Combatant{}, nil, fmt.Errorf("ensure dnd character: %w", err)
	}
	applyDnDPlayerLayer(&playerStats, dndChar)
	applyDnDEquipmentLayer(&playerStats, dndChar, equip)
	applyDnDHPScaling(&playerStats, dndChar)
	applyClassPassives(&playerStats, &playerMods, dndChar)
	applyRacePassives(&playerStats, &playerMods, dndChar)
	applySubclassPassives(&playerStats, &playerMods, dndChar)
	applyMagicItemEffects(&playerStats, &playerMods, userID)
	trySimAutoArm(dndChar)
	if firedName, fired := applyArmedAbility(dndChar, &playerMods); fired {
		slog.Info("dnd: armed ability fired (turn-based build)", "user", userID, "ability", firedName)
	}

	enemyStats, enemyMods := monster.toCombatStats()
	// Tier scaling mirrors runZoneCombat: only raise AC/AttackBonus to a
	// tier floor — boss/elite stat blocks already encode their challenge, so
	// we never double-scale a block that's already above the floor.
	if tier > 1 {
		floorAC := dndDungeonACBase + tier
		if enemyStats.AC < floorAC {
			enemyStats.AC = floorAC
		}
		floorAB := dndDungeonAtkBase + tier
		if enemyStats.AttackBonus < floorAB {
			enemyStats.AttackBonus = floorAB
		}
	}

	// DM mood tilts: monster Attack delta + player initiative bias.
	enemyStats.Attack += tilt.EnemyAttackDelta
	if enemyStats.Attack < 1 {
		enemyStats.Attack = 1
	}
	playerMods.InitiativeBias += tilt.InitiativeBias

	displayName, _ := loadDisplayName(userID)
	player = Combatant{
		Name:     displayName,
		Stats:    playerStats,
		Mods:     playerMods,
		IsPlayer: true,
	}
	enemy = Combatant{
		Name:    monster.Name,
		Stats:   enemyStats,
		Mods:    enemyMods,
		Ability: monster.Ability,
	}
	return player, enemy, dndChar, nil
}

// combatantsForSession reconstructs the Combatant pair for an in-flight solo
// CombatSession — the shape every caller wanted before parties existed. It is
// partyCombatantsForSession reduced to seat 0, and it errors rather than
// silently dropping the rest of a party's roster on the floor.
func (p *AdventurePlugin) combatantsForSession(sess *CombatSession) (player Combatant, enemy Combatant, err error) {
	if sess.IsParty() {
		return Combatant{}, Combatant{}, fmt.Errorf(
			"combat session %s seats %d players; use partyCombatantsForSession", sess.SessionID, sess.RosterSize())
	}
	players, e, err := p.partyCombatantsForSession(sess)
	if err != nil {
		return Combatant{}, Combatant{}, err
	}
	return *players[0], *e, nil
}

// partyCombatantsForSession reconstructs the seated roster and the enemy for an
// in-flight CombatSession. It reloads the zone run for the DM mood + tier and
// looks the enemy up in the bestiary by the session's EnemyID. The combatants
// carry no HP — the turn engine reads that from the session row and the
// participant rows.
//
// Every seat is rebuilt from *its own* player: their sheet, their equipment,
// their passives, their magic items. That is N times the per-round DB chatter
// combatantsForSession already had (project_combat_session_cache_deferred), and
// a party of 3 pays it three times over. Solo — every fight that has ever run,
// and the whole balance corpus — still issues exactly one build.
func (p *AdventurePlugin) partyCombatantsForSession(sess *CombatSession) ([]*Combatant, *Combatant, error) {
	run, rerr := getZoneRun(sess.RunID)
	if rerr != nil {
		return nil, nil, fmt.Errorf("load zone run: %w", rerr)
	}
	if run == nil {
		return nil, nil, fmt.Errorf("combat session %s: zone run %s not found", sess.SessionID, sess.RunID)
	}
	monster, ok := dndBestiary[sess.EnemyID]
	if !ok {
		return nil, nil, fmt.Errorf("combat session %s: enemy %q not in bestiary", sess.SessionID, sess.EnemyID)
	}
	zone := zoneOrFallback(run.ZoneID)

	seats := sess.SeatUserIDs()
	players := make([]*Combatant, len(seats))
	var enemy Combatant
	for seat, uid := range seats {
		player, e, _, err := p.buildZoneCombatants(id.UserID(uid), monster, int(zone.Tier), run.DMMood)
		if err != nil {
			return nil, nil, fmt.Errorf("seat %d (%s): %w", seat, uid, err)
		}
		// Fold any fight-scoped buffs this seat's mid-fight !cast / !consume
		// layered on back onto their freshly-rebuilt combatant. The depleting
		// one-shots (ward/spore/…) live on their persisted statuses and flow
		// through the turn engine's resume/commit cycle, so only the persistent
		// stat deltas are applied here — and only that seat's own.
		applySessionBuffs(&player, sess.actorStatusesForSeat(seat))
		players[seat] = &player
		if seat == 0 {
			// The enemy build reads only (monster, tier, dmMood): every seat
			// rebuilds the identical stat block, so seat 0's copy is the fight's.
			// Only the *player* half of the build varies by seat.
			enemy = e
		}
	}
	return players, &enemy, nil
}

// applySessionBuffs re-derives the persistent stat effect of every mid-fight
// buff onto one rebuilt character. The buffs are stored as accumulated deltas
// (diffTurnBuff produced them against that character's state at cast time), so
// re-applying them to a deterministic rebuild reproduces the same totals every
// round without double-counting. It takes ActorStatuses rather than the whole
// session because buffs are per-caster: each seat folds in only its own.
func applySessionBuffs(player *Combatant, s ActorStatuses) {
	player.Stats.AC += s.BuffACBonus
	player.Stats.AttackBonus += s.BuffAtkBonus
	player.Stats.Speed += s.BuffSpeedBonus
	player.Stats.CritRate += s.BuffCritRate
	player.Mods.DamageBonus += s.BuffDamageBonus
	player.Mods.PetAttackProc += s.BuffPetProc
	player.Mods.PetAttackDmg += s.BuffPetDmg
	player.Mods.SpiritWeaponProc += s.BuffSpiritProc
	player.Mods.SpiritWeaponDmg += s.BuffSpiritDmg
	if s.BuffDamageReductMul > 0 {
		player.Mods.DamageReduct *= s.BuffDamageReductMul
	}
}