use crate::{
    models::{
        item::{Item, SkillType, StatType, BuffImpact},
        user::User
    },
    db::DBTrans,
    DResult,
};
use rand::{self, Rng};
use chrono::Utc;
use std::collections::BTreeMap;

pub fn calculate_total_stats_skills_for_user(target_item: &mut Item, user: &User) {
    target_item.total_stats = BTreeMap::new();
    // 1: Start with total stats = raw stats
    for stat_type in StatType::values() {
        target_item.total_stats.insert(stat_type.clone(),
                                       *user.raw_stats.get(&stat_type).unwrap_or(&0.0));
    }
    // 2: Apply stat (de)buffs...
    for buff in &target_item.temporary_buffs {
        for impact in &buff.impacts {
            match impact {
                BuffImpact::ChangeStat { stat, magnitude } => {
                    target_item.total_stats.entry(stat.clone())
                    .and_modify(|old_value| *old_value = (*old_value + magnitude.clone() as f64).max(0.0))
                        .or_insert((*magnitude).max(0) as f64);
                }
                _ => {}
            }
        }
    }
    // 3: Total skills = raw skills
    target_item.total_skills = BTreeMap::new();
    for skill_type in SkillType::values() {
        target_item.total_skills.insert(skill_type.clone(),
                                        *user.raw_skills.get(&skill_type).unwrap_or(&0.0));
    }
    // 4: Adjust skills by stats
    let brn = *target_item.total_stats.get(&StatType::Brains).unwrap_or(&0.0);
    let sen = *target_item.total_stats.get(&StatType::Senses).unwrap_or(&0.0); 
    let brw = *target_item.total_stats.get(&StatType::Brawn).unwrap_or(&0.0);
    let refl = *target_item.total_stats.get(&StatType::Reflexes).unwrap_or(&0.0);
    let end = *target_item.total_stats.get(&StatType::Endurance).unwrap_or(&0.0);
    let col = *target_item.total_stats.get(&StatType::Cool).unwrap_or(&0.0);
    target_item.total_skills.entry(SkillType::Appraise)
        .and_modify(|sk| *sk += brn * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Appraise)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Blades)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Blades)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Bombs)
        .and_modify(|sk| *sk += brn * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Bombs)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Chemistry)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Climb)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Climb)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Clubs)
        .and_modify(|sk| *sk += brw * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Clubs)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Craft)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Dodge)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Dodge)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fish)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fish)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fists)
        .and_modify(|sk| *sk += brw * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fists)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Focus)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Focus)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fuck)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Fuck)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Hack)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Locksmith)
        .and_modify(|sk| *sk += brn * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Locksmith)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Medic)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Persuade)
        .and_modify(|sk| *sk += brn * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Persuade)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Pilot)
        .and_modify(|sk| *sk += brn * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Pilot)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Pistols)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Pistols)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Quickdraw)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Quickdraw)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Repair)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Rifles)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Rifles)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Scavenge)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Scavenge)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Science)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Sneak)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Sneak)
        .and_modify(|sk| *sk += col * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Spears)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Spears)
        .and_modify(|sk| *sk += end * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Swim)
        .and_modify(|sk| *sk += end).or_insert(brn);
    target_item.total_skills.entry(SkillType::Teach)
        .and_modify(|sk| *sk += brn).or_insert(brn);
    target_item.total_skills.entry(SkillType::Throw)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Throw)
        .and_modify(|sk| *sk += brw * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Track)
        .and_modify(|sk| *sk += sen).or_insert(brn);
    target_item.total_skills.entry(SkillType::Whips)
        .and_modify(|sk| *sk += sen * 0.5).or_insert(brn * 0.5);
    target_item.total_skills.entry(SkillType::Whips)
        .and_modify(|sk| *sk += refl * 0.5).or_insert(brn * 0.5);
    // 5: Apply skill (de)buffs...
    for buff in &target_item.temporary_buffs {
        for impact in &buff.impacts {
            match impact {
                BuffImpact::ChangeSkill { skill, magnitude } => {
                    target_item.total_skills.entry(skill.clone())
                    .and_modify(|old_value| *old_value = (*old_value + magnitude.clone() as f64).max(0.0))
                        .or_insert((*magnitude).max(0) as f64);
                }
                _ => {}
            }
        }
    }
}
    
pub fn calc_level_gap(who: &Item, skill: &SkillType, diff_level: f64) -> f64 {
    let user_level = who.total_skills.get(skill).unwrap_or(&0.0);
    diff_level - user_level.clone()
}

pub fn skill_check_fn(level_gap: f64) -> f64 {
    const K: f64 = 0.3662040962227033; // log 3 / 3
    rand::thread_rng().gen::<f64>() - 1.0 / (1.0 + (-K * (level_gap as f64)).exp())
}

// Rolls the die to determine if a player pulls off something that requires a skill.
// It is a number between -1 and 1.
// Non-negative numbers mean they pulled it off, positive mean they didn't, with
// more positive numbers meaning they did a better job, and more negative numbers
// meaning it went really badly.
// If level = raw skill, there is a 50% chance of succeeding.
//    level = raw skill + 3, there is a 75% chance of succeeding.
//    level = raw skill - 3, there is a 25% chance of succeeding.
// Outside those differences, it follows the logistic function:
//   Difference:     -5    -4    -3    -2  -1   0   1   2   3   4    5
//   Probability:    13%  19%   25%   32% 41% 50% 59% 68% 75%  81% 86%
pub fn skill_check_only(who: &Item, skill: &SkillType, diff_level: f64) -> f64 {
    skill_check_fn(calc_level_gap(who, skill, diff_level))
}

// Note: Caller must save who because skills might update.
// Don't return error if skillcheck fails, it can fail but still grind.
pub async fn skill_check_and_grind(trans: &DBTrans, who: &mut Item, skill: &SkillType, diff_level: f64) -> DResult<f64> {
    let gap = calc_level_gap(who, skill, diff_level);
    let result = skill_check_fn(gap);

    // If the skill gap is 0, probability of learning is 0.5
    // If the skill gap is 1, probability of learning is 0.4 (20% less), and so on (exponential decrease).
    const LAMBDA: f64 = -0.2231435513142097; // log 0.8
    if who.item_type == "player" && rand::thread_rng().gen::<f64>() < 0.5 * (LAMBDA * (gap as f64)).exp() {
        if let Some((sess, _sess_dat)) = trans.find_session_for_player(&who.item_code).await? {
            if let Some(mut user) = trans.find_by_username(&who.item_code).await? {
                if *user.raw_skills.get(skill).unwrap_or(&0.0) >= 15.0 ||
                    !user.last_skill_improve.get(skill)
                    .map(|t| (Utc::now() - *t).num_seconds() > 60).unwrap_or(true) {
                    return Ok(result)
                }
                user.raw_skills.entry(skill.clone()).and_modify(|raw| *raw += 0.01).or_insert(0.01);
                user.last_skill_improve.insert(skill.clone(), Utc::now());
                trans.queue_for_session(&sess,
                                        Some(&format!("Your raw {} is now {:.2}\n",
                                                      skill.display(), user.raw_skills
                                                      .get(skill).unwrap_or(&0.0)))).await?;
                trans.save_user_model(&user).await?;
                calculate_total_stats_skills_for_user(who, &user);
            }
        }
    }

    Ok(result)
}