// Copyright (C) 2025 Emilis Bliūdžius
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
use core::{num::NonZeroU8, ops::Not};

use super::Result;
use crate::{
    character::CharacterId,
    diedto::DiedTo,
    error::GameError,
    game::{
        Village,
        night::changes::{ChangesLookup, NightChange},
    },
    player::Protection,
};

#[derive(Debug, PartialEq)]
pub enum KillOutcome {
    Single(CharacterId, DiedTo),
    Guarding {
        original_killer: CharacterId,
        original_target: CharacterId,
        original_kill: DiedTo,
        guardian: CharacterId,
        night: NonZeroU8,
    },
}

impl KillOutcome {
    pub fn apply_to_village(
        self,
        village: &mut Village,
        recorded_changes: Option<&mut Vec<NightChange>>,
    ) -> Result<()> {
        match self {
            KillOutcome::Single(character_id, died_to) => {
                village
                    .character_by_id_mut(character_id)?
                    .kill(died_to.clone());
                if let DiedTo::Militia { killer, .. } = died_to
                    && let Some(existing) = village
                        .character_by_id_mut(killer)?
                        .militia_mut()?
                        .replace(character_id)
                {
                    log::error!("militia kill after already recording a kill on {existing}");
                    return Err(GameError::MilitiaSpent);
                }

                Ok(())
            }
            KillOutcome::Guarding {
                original_killer,
                original_target,
                original_kill,
                guardian,
                night,
            } => {
                // check if guardian exists before we mutably borrow killer, which would
                // prevent us from borrowing village to check after.
                village.character_by_id(guardian)?;
                let guardian_kill = DiedTo::GuardianProtecting {
                    night,
                    source: guardian,
                    protecting: original_target,
                    protecting_from: original_killer,
                    protecting_from_cause: Box::new(original_kill.clone()),
                };
                if let Some(recorded_changes) = recorded_changes {
                    recorded_changes.push(NightChange::Kill {
                        target: original_killer,
                        died_to: guardian_kill.clone(),
                    });
                }
                village
                    .character_by_id_mut(original_killer)?
                    .kill(guardian_kill);
                village.character_by_id_mut(guardian)?.kill(original_kill);
                Ok(())
            }
        }
    }
}

fn resolve_protection(
    killer: CharacterId,
    killed_with: &DiedTo,
    target: CharacterId,
    protection: &Protection,
    night: NonZeroU8,
) -> Option<KillOutcome> {
    match protection {
        Protection::Guardian {
            source,
            guarding: true,
        } => Some(KillOutcome::Guarding {
            original_killer: killer,
            guardian: *source,
            original_target: target,
            original_kill: killed_with.clone(),
            night,
        }),
        Protection::Guardian {
            source: _,
            guarding: false,
        }
        | Protection::Vindicator { .. }
        | Protection::Protector { source: _ } => None,
    }
}

pub fn resolve_kill(
    changes: &mut ChangesLookup<'_>,
    target: CharacterId,
    died_to: &DiedTo,
    night: u8,
    village: &Village,
) -> Result<Option<KillOutcome>> {
    if let DiedTo::MapleWolf {
        source,
        night,
        starves_if_fails: true,
    } = died_to
        && let Some(protection) = changes.protected_take(target)
    {
        return Ok(Some(
            resolve_protection(*source, died_to, target, &protection, *night).unwrap_or(
                KillOutcome::Single(*source, DiedTo::MapleWolfStarved { night: *night }),
            ),
        ));
    }
    if let DiedTo::Wolfpack {
        night,
        killing_wolf,
    } = died_to
        && let Some(ss_source) = changes.shapeshifter()
    {
        let killing_wolf = village.character_by_id(*killing_wolf)?;

        match changes.protected_take(target) {
            Some(protection) => {
                return Ok(resolve_protection(
                    killing_wolf.character_id(),
                    died_to,
                    target,
                    &protection,
                    *night,
                ));
            }
            None => {
                // Wolf kill went through -- can kill shifter
                return Ok(Some(KillOutcome::Single(
                    *ss_source,
                    DiedTo::Shapeshift {
                        into: target,
                        night: *night,
                    },
                )));
            }
        };
    }

    let protection = match changes.protected_take(target) {
        Some(prot) => prot,
        None => return Ok(Some(KillOutcome::Single(target, died_to.clone()))),
    };

    match protection {
        Protection::Guardian {
            source,
            guarding: true,
        } => Ok(Some(KillOutcome::Guarding {
            original_killer: died_to
                .killer()
                .ok_or(GameError::GuardianInvalidOriginalKill)?,
            original_target: target,
            original_kill: died_to.clone(),
            guardian: source,
            night: NonZeroU8::new(night).unwrap(),
        })),
        Protection::Guardian {
            guarding: false, ..
        }
        | Protection::Vindicator { .. }
        | Protection::Protector { .. } => Ok(None),
    }
}