// ─── Skill Slice ──────────────────────────────────────────────────────────────
// Manages skills, studying, and skill progress

import type { StateCreator } from 'zustand';
import type { GameState, StudyTarget, SkillUpgradeChoice } from '../types';
import { SKILLS_DEF, SPELLS_DEF, getStudySpeedMultiplier, getStudyCostMultiplier } from '../constants';
import { getUpgradesForSkillAtMilestone, getNextTierSkill, getTierMultiplier } from '../skill-evolution';
import { computeEffects } from '../upgrade-effects';

export interface SkillSlice {
  // State
  skills: Record<string, number>;
  skillProgress: Record<string, number>;
  skillUpgrades: Record<string, string[]>;
  skillTiers: Record<string, number>;
  currentStudyTarget: StudyTarget | null;
  parallelStudyTarget: StudyTarget | null;

  // Actions
  startStudyingSkill: (skillId: string) => void;
  startStudyingSpell: (spellId: string) => void;
  startParallelStudySkill: (skillId: string) => void;
  cancelStudy: () => void;
  cancelParallelStudy: () => void;
  selectSkillUpgrade: (skillId: string, upgradeId: string) => void;
  deselectSkillUpgrade: (skillId: string, upgradeId: string) => void;
  commitSkillUpgrades: (skillId: string, upgradeIds: string[], milestone: 5 | 10) => void;
  tierUpSkill: (skillId: string) => void;

  // Getters
  getSkillUpgradeChoices: (skillId: string, milestone: 5 | 10) => { available: SkillUpgradeChoice[]; selected: string[] };
}

export const createSkillSlice = (
  set: StateCreator<GameState>['set'],
  get: () => GameState
): SkillSlice => ({
  skills: {},
  skillProgress: {},
  skillUpgrades: {},
  skillTiers: {},
  currentStudyTarget: null,
  parallelStudyTarget: null,

  startStudyingSkill: (skillId: string) => {
    const state = get();
    const sk = SKILLS_DEF[skillId];
    if (!sk) return;

    const currentLevel = state.skills[skillId] || 0;
    if (currentLevel >= sk.max) return;

    // Check prerequisites
    if (sk.req) {
      for (const [r, rl] of Object.entries(sk.req)) {
        if ((state.skills[r] || 0) < rl) return;
      }
    }

    const costMult = getStudyCostMultiplier(state.skills);
    const totalCost = Math.floor(sk.base * (currentLevel + 1) * costMult);
    const manaCostPerHour = totalCost / sk.studyTime;

    set({
      currentAction: 'study',
      currentStudyTarget: {
        type: 'skill',
        id: skillId,
        progress: state.skillProgress[skillId] || 0,
        required: sk.studyTime,
        manaCostPerHour,
      },
      log: [`📚 Started studying ${sk.name}... (${Math.floor(manaCostPerHour)} mana/hour)`, ...state.log.slice(0, 49)],
    });
  },

  startStudyingSpell: (spellId: string) => {
    const state = get();
    const sp = SPELLS_DEF[spellId];
    if (!sp || state.spells[spellId]?.learned) return;

    const costMult = getStudyCostMultiplier(state.skills);
    const totalCost = Math.floor(sp.unlock * costMult);
    const studyTime = sp.studyTime || (sp.tier * 4);
    const manaCostPerHour = totalCost / studyTime;

    set({
      currentAction: 'study',
      currentStudyTarget: {
        type: 'spell',
        id: spellId,
        progress: state.spells[spellId]?.studyProgress || 0,
        required: studyTime,
        manaCostPerHour,
      },
      spells: {
        ...state.spells,
        [spellId]: {
          ...(state.spells[spellId] || { learned: false, level: 0 }),
          studyProgress: state.spells[spellId]?.studyProgress || 0,
        },
      },
      log: [`📚 Started studying ${sp.name}... (${Math.floor(manaCostPerHour)} mana/hour)`, ...state.log.slice(0, 49)],
    });
  },

  startParallelStudySkill: (skillId: string) => {
    const state = get();
    if (state.parallelStudyTarget) return;
    if (!state.currentStudyTarget) return;

    const sk = SKILLS_DEF[skillId];
    if (!sk) return;

    const currentLevel = state.skills[skillId] || 0;
    if (currentLevel >= sk.max) return;

    if (state.currentStudyTarget.id === skillId) return;

    set({
      parallelStudyTarget: {
        type: 'skill',
        id: skillId,
        progress: state.skillProgress[skillId] || 0,
        required: sk.studyTime,
        manaCostPerHour: 0, // Parallel study doesn't cost extra
      },
      log: [`📚 Started parallel study of ${sk.name}... (50% speed)`, ...state.log.slice(0, 49)],
    });
  },

  cancelStudy: () => {
    const state = get();
    if (!state.currentStudyTarget) return;

    const savedProgress = state.currentStudyTarget.progress;
    const log = ['📖 Study paused. Progress saved.', ...state.log.slice(0, 49)];

    if (state.currentStudyTarget.type === 'skill') {
      set({
        currentStudyTarget: null,
        currentAction: 'meditate',
        skillProgress: {
          ...state.skillProgress,
          [state.currentStudyTarget.id]: savedProgress,
        },
        log,
      });
    } else {
      set({
        currentStudyTarget: null,
        currentAction: 'meditate',
        spells: {
          ...state.spells,
          [state.currentStudyTarget.id]: {
            ...(state.spells[state.currentStudyTarget.id] || { learned: false, level: 0 }),
            studyProgress: savedProgress,
          },
        },
        log,
      });
    }
  },

  cancelParallelStudy: () => {
    set((state) => {
      if (!state.parallelStudyTarget) return state;
      return {
        parallelStudyTarget: null,
        log: ['📖 Parallel study cancelled.', ...state.log.slice(0, 49)],
      };
    });
  },

  selectSkillUpgrade: (skillId: string, upgradeId: string) => {
    set((state) => {
      const current = state.skillUpgrades?.[skillId] || [];
      if (current.includes(upgradeId)) return state;
      if (current.length >= 2) return state;
      return {
        skillUpgrades: {
          ...state.skillUpgrades,
          [skillId]: [...current, upgradeId],
        },
      };
    });
  },

  deselectSkillUpgrade: (skillId: string, upgradeId: string) => {
    set((state) => {
      const current = state.skillUpgrades?.[skillId] || [];
      return {
        skillUpgrades: {
          ...state.skillUpgrades,
          [skillId]: current.filter(id => id !== upgradeId),
        },
      };
    });
  },

  commitSkillUpgrades: (skillId: string, upgradeIds: string[], milestone: 5 | 10) => {
    set((state) => {
      const existingUpgrades = state.skillUpgrades?.[skillId] || [];
      const otherMilestoneUpgrades = existingUpgrades.filter(
        id => milestone === 5 ? id.includes('_l10') : id.includes('_l5')
      );
      return {
        skillUpgrades: {
          ...state.skillUpgrades,
          [skillId]: [...otherMilestoneUpgrades, ...upgradeIds],
        },
      };
    });
  },

  tierUpSkill: (skillId: string) => {
    const state = get();
    const baseSkillId = skillId.includes('_t') ? skillId.split('_t')[0] : skillId;
    const currentTier = state.skillTiers?.[baseSkillId] || 1;
    const nextTier = currentTier + 1;

    if (nextTier > 5) return;

    const nextTierSkillId = `${baseSkillId}_t${nextTier}`;

    set({
      skillTiers: {
        ...state.skillTiers,
        [baseSkillId]: nextTier,
      },
      skills: {
        ...state.skills,
        [nextTierSkillId]: 0,
        [skillId]: 0,
      },
      skillProgress: {
        ...state.skillProgress,
        [skillId]: 0,
        [nextTierSkillId]: 0,
      },
      skillUpgrades: {
        ...state.skillUpgrades,
        [nextTierSkillId]: [],
        [skillId]: [],
      },
      log: [`🌟 ${SKILLS_DEF[baseSkillId]?.name || baseSkillId} evolved to Tier ${nextTier}!`, ...state.log.slice(0, 49)],
    });
  },

  getSkillUpgradeChoices: (skillId: string, milestone: 5 | 10) => {
    const state = get();
    const baseSkillId = skillId.includes('_t') ? skillId.split('_t')[0] : skillId;
    const tier = state.skillTiers?.[baseSkillId] || 1;

    const available = getUpgradesForSkillAtMilestone(skillId, milestone, state.skillTiers || {});
    const selected = (state.skillUpgrades?.[skillId] || []).filter(id =>
      available.some(u => u.id === id)
    );

    return { available, selected };
  },
});

// Process study progress (called during tick)
export function processStudy(state: GameState, deltaHours: number): Partial<GameState> {
  if (state.currentAction !== 'study' || !state.currentStudyTarget) return {};

  const target = state.currentStudyTarget;
  const studySpeedMult = getStudySpeedMultiplier(state.skills);
  const progressGain = deltaHours * studySpeedMult;
  const manaCost = progressGain * target.manaCostPerHour;

  let rawMana = state.rawMana;
  let totalManaGathered = state.totalManaGathered;
  let skills = state.skills;
  let skillProgress = state.skillProgress;
  let spells = state.spells;
  const log = [...state.log];

  if (rawMana >= manaCost) {
    rawMana -= manaCost;
    totalManaGathered += manaCost;

    const newProgress = target.progress + progressGain;

    if (newProgress >= target.required) {
      // Study complete
      if (target.type === 'skill') {
        const skillId = target.id;
        const currentLevel = skills[skillId] || 0;
        skills = { ...skills, [skillId]: currentLevel + 1 };
        skillProgress = { ...skillProgress, [skillId]: 0 };
        log.unshift(`✅ ${SKILLS_DEF[skillId]?.name} Lv.${currentLevel + 1} mastered!`);
      } else if (target.type === 'spell') {
        const spellId = target.id;
        spells = {
          ...spells,
          [spellId]: { learned: true, level: 1, studyProgress: 0 },
        };
        log.unshift(`📖 ${SPELLS_DEF[spellId]?.name} learned!`);
      }

      return {
        rawMana,
        totalManaGathered,
        skills,
        skillProgress,
        spells,
        currentStudyTarget: null,
        currentAction: 'meditate',
        log,
      };
    }

    return {
      rawMana,
      totalManaGathered,
      currentStudyTarget: { ...target, progress: newProgress },
    };
  }

  // Not enough mana
  log.unshift('⚠️ Not enough mana to continue studying. Progress saved.');

  if (target.type === 'skill') {
    return {
      currentStudyTarget: null,
      currentAction: 'meditate',
      skillProgress: { ...skillProgress, [target.id]: target.progress },
      log,
    };
  } else {
    return {
      currentStudyTarget: null,
      currentAction: 'meditate',
      spells: {
        ...spells,
        [target.id]: {
          ...(spells[target.id] || { learned: false, level: 0 }),
          studyProgress: target.progress,
        },
      },
      log,
    };
  }
}