use super::api::{Api, ApiError, Profession, Skill, Specialization};
use byteorder::{ReadBytesExt, WriteBytesExt, LE};
use num_enum::{IntoPrimitive, TryFromPrimitive};
use std::{convert::TryFrom, fmt, io::Cursor, str::FromStr};
use thiserror::Error;

#[derive(Error, Debug)]
pub enum ChatlinkError {
    #[error("Error accessing the API")]
    ApiError(#[from] ApiError),
    #[error("The input link is malformed")]
    MalformedInput,
}

impl From<std::io::Error> for ChatlinkError {
    fn from(_err: std::io::Error) -> Self {
        panic!("The reading cursor should never return an error!");
    }
}

impl From<base64::DecodeError> for ChatlinkError {
    fn from(_: base64::DecodeError) -> Self {
        ChatlinkError::MalformedInput
    }
}

impl From<num_enum::TryFromPrimitiveError<TraitChoice>> for ChatlinkError {
    fn from(_: num_enum::TryFromPrimitiveError<TraitChoice>) -> Self {
        ChatlinkError::MalformedInput
    }
}

impl From<num_enum::TryFromPrimitiveError<Legend>> for ChatlinkError {
    fn from(_: num_enum::TryFromPrimitiveError<Legend>) -> Self {
        ChatlinkError::MalformedInput
    }
}

/// Represents the selected trait.
#[repr(u8)]
#[derive(Debug, PartialEq, Eq, Hash, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
pub enum TraitChoice {
    None = 0,
    Top = 1,
    Middle = 2,
    Bottom = 3,
}

impl FromStr for TraitChoice {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let lower = s.to_lowercase();
        match &lower as &str {
            "" | "none" => Ok(TraitChoice::None),
            "top" => Ok(TraitChoice::Top),
            "mid" | "middle" => Ok(TraitChoice::Middle),
            "bot" | "bottom" => Ok(TraitChoice::Bottom),
            _ => Err(()),
        }
    }
}

impl fmt::Display for TraitChoice {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let result = match *self {
            TraitChoice::None => "none",
            TraitChoice::Top => "top",
            TraitChoice::Middle => "mid",
            TraitChoice::Bottom => "bot",
        };
        write!(f, "{}", result)
    }
}

/// Represents a revenenant legend.
#[repr(u8)]
#[derive(Debug, PartialEq, Eq, Hash, Copy, Clone, IntoPrimitive, TryFromPrimitive)]
pub enum Legend {
    None = 0,
    Dragon = 13,
    Assassin = 14,
    Dwarf = 15,
    Demon = 16,
    Renegade = 17,
    Centaur = 18,
}

impl Legend {
    pub fn api_id(self) -> Option<String> {
        Some(
            match self {
                Legend::None => return None,
                Legend::Dragon => "Legend1",
                Legend::Assassin => "Legend2",
                Legend::Dwarf => "Legend3",
                Legend::Demon => "Legend4",
                Legend::Renegade => "Legend5",
                Legend::Centaur => "Legend6",
            }
            .to_owned(),
        )
    }
}

impl FromStr for Legend {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let lower = s.to_lowercase();
        match &lower as &str {
            "" | "none" => Ok(Legend::None),
            "dragon" | "glint" => Ok(Legend::Dragon),
            "assassin" | "shiro" => Ok(Legend::Assassin),
            "dwarf" | "jalis" => Ok(Legend::Dwarf),
            "demon" | "mallyx" => Ok(Legend::Demon),
            "renegade" | "kalla" => Ok(Legend::Renegade),
            "centaur" | "ventari" => Ok(Legend::Centaur),
            _ => Err(()),
        }
    }
}

#[derive(Debug, Clone)]
pub enum ExtraData {
    None,
    Legends([Legend; 4]),
}

/// Represents a traitline.
///
/// A traitline consists of the chosen specialization including 3 possible trait choices.
pub type Traitline = (Specialization, [TraitChoice; 3]);

pub const SKILL_COUNT: usize = 5;
pub const TRAITLINE_COUNT: usize = 3;
pub const LEGEND_COUNT: usize = 4;

/// The code for the revenant profession.
pub const CODE_REVENANT: u32 = 9;

pub const EMPTY_SKILLS: [Option<Skill>; SKILL_COUNT] = [None, None, None, None, None];
pub const EMPTY_TRAITLINES: [Option<Traitline>; TRAITLINE_COUNT] = [None, None, None];

/// Represents a build template.
///
/// This struct is made with the same limitations as the game imposes. That is, even though the
/// renderer can support more than three traitlines, this template will only allow you to take
/// three.
#[derive(Debug)]
pub struct BuildTemplate {
    /// Profession of this build.
    profession: Profession,
    /// The skills of the build.
    ///
    /// Each slot can either contain a slot or be empty. A maximum of 5 skills are allowed (heal, 3
    /// utilities and elite).
    skills: [Option<Skill>; SKILL_COUNT],
    /// The traitlines of the build.
    traitlines: [Option<Traitline>; TRAITLINE_COUNT],
    /// Extra data, such as revenant legends or ranger pets.
    extra_data: ExtraData,
}

impl BuildTemplate {
    /// Creates a template with the given skills and traitlines.
    ///
    /// If there are more than 5 skills or 3 traitlines given, the function will return `None`.
    pub fn new(
        profession: Profession,
        skills: &[Skill],
        traitlines: &[Traitline],
        extra_data: ExtraData,
    ) -> Option<BuildTemplate> {
        if skills.len() > SKILL_COUNT {
            return None;
        }
        if traitlines.len() > TRAITLINE_COUNT {
            return None;
        }
        let mut skill_array = [None, None, None, None, None];
        for (i, skill) in skills.iter().enumerate() {
            skill_array[i] = Some(skill.clone());
        }
        let mut trait_array = [None, None, None];
        for (i, traitline) in traitlines.iter().enumerate() {
            trait_array[i] = Some(traitline.clone());
        }
        Some(BuildTemplate {
            profession,
            skills: skill_array,
            traitlines: trait_array,
            extra_data,
        })
    }

    /// Returns the profession of this build.
    pub fn profession(&self) -> &Profession {
        &self.profession
    }

    /// Returns the skills of this build.
    pub fn skills(&self) -> &[Option<Skill>] {
        &self.skills
    }

    /// Returns the number of actually equipped skills.
    pub fn skill_count(&self) -> u32 {
        self.skills.iter().filter(|x| x.is_some()).count() as u32
    }

    /// Returns the traitlines of this build.
    pub fn traitlines(&self) -> &[Option<Traitline>] {
        &self.traitlines
    }

    /// Returns the number of actually equipped specializations.
    pub fn traitline_count(&self) -> u32 {
        self.traitlines.iter().filter(|x| x.is_some()).count() as u32
    }

    /// Returns the extra data associated with this build template.
    pub fn extra_data(&self) -> &ExtraData {
        &self.extra_data
    }

    /// Serializes this build template into a chat link.
    ///
    /// The returned link is ready to be copy-and-pasted into Guild Wars 2.
    pub fn chatlink(&self) -> String {
        let mut bytes = vec![0x0Du8];
        let prof_byte = self.profession().code as u8;
        bytes.push(prof_byte);

        for traitline in self.traitlines().iter() {
            if let Some((spec, choices)) = traitline {
                bytes.push(spec.id as u8);
                let selected = choices[0] as u8 | (choices[1] as u8) << 2 | (choices[2] as u8) << 4;
                bytes.push(selected);
            } else {
                bytes.push(0);
                bytes.push(0);
            }
        }

        for skill in self.skills() {
            // Terrestric
            match skill {
                None => {
                    bytes.push(0);
                    bytes.push(0);
                }
                Some(s) => {
                    let palette_id = self.profession().skill_id_to_palette_id(s.id).unwrap_or(0);
                    bytes.write_u16::<LE>(palette_id as u16).unwrap();
                }
            }
            // Aquatic
            bytes.push(0);
            bytes.push(0);
        }

        match *self.extra_data() {
            ExtraData::None => {
                bytes.extend_from_slice(&[0, 0, 0, 0]);
            }
            ExtraData::Legends(ref legends) => {
                bytes.extend(legends.iter().map(|l| *l as u8));
            }
        }

        // 12 more bytes are used to save the order of the skills in the inactive revenant
        // utilities (the active ones are saved in the normal skill slots).
        // The order is terrestric 1/2/3 and then aquatic 1/2/3, with 2 bytes per skill.
        // We don't care about that, so just do whatever.
        for _ in 0..12 {
            bytes.push(0);
        }

        format!("[&{}]", base64::encode(&bytes))
    }

    /// Takes a chat link from the game and parses it into a BuildTemplate.
    ///
    /// This needs api acccess in order to fetch the relevant skill and trait data.
    pub fn from_chatlink(api: &mut Api, input: &str) -> Result<BuildTemplate, ChatlinkError> {
        if !input.starts_with("[&") || !input.ends_with(']') {
            return Err(ChatlinkError::MalformedInput);
        }
        let inner = &input[2..input.len() - 1];
        let mut bytes = base64::decode(inner)?;

        // Magic number
        if bytes.len() != 44 || bytes[0] != 0x0D {
            return Err(ChatlinkError::MalformedInput);
        }
        bytes.remove(0);

        let mut reader = Cursor::new(bytes);

        let profession = code_to_profession(api, reader.read_u8()? as u32)?;

        let mut traitlines = EMPTY_TRAITLINES;
        for i in traitlines.iter_mut() {
            let spec_id = reader.read_u8()?;
            let trait_choices = reader.read_u8()?;
            if spec_id == 0 {
                continue;
            }

            let spec = api.get_specializations(&[spec_id as u32])?.remove(0);
            let c_0 = TraitChoice::try_from(trait_choices & 0x3)?;
            let c_1 = TraitChoice::try_from((trait_choices >> 2) & 0x3)?;
            let c_2 = TraitChoice::try_from((trait_choices >> 4) & 0x3)?;
            *i = Some((spec, [c_0, c_1, c_2]));
        }

        let mut skills = EMPTY_SKILLS;
        for i in skills.iter_mut() {
            // Terrestrial
            let palette_id = reader.read_u16::<LE>()? as u32;
            if palette_id != 0 {
                let skill_id = profession
                    .palette_id_to_skill_id(palette_id)
                    .ok_or(ChatlinkError::MalformedInput)?;
                let skill = api.get_skills(&[skill_id])?.remove(0);
                *i = Some(skill);
            }

            // Aquatic
            reader.read_u16::<LE>()?;
        }

        let extra_data = match profession.code {
            CODE_REVENANT => {
                let mut legends = [Legend::None; LEGEND_COUNT];
                for i in legends.iter_mut() {
                    *i = Legend::try_from(reader.read_u8()?)?;
                }
                ExtraData::Legends(legends)
            }
            _ => ExtraData::None,
        };

        Ok(BuildTemplate {
            profession,
            traitlines,
            skills,
            extra_data,
        })
    }
}

fn code_to_profession(api: &mut Api, code: u32) -> Result<Profession, ChatlinkError> {
    let professions = api.get_all_professions()?;
    professions
        .into_iter()
        .find(|p| p.code == code)
        .ok_or(ChatlinkError::MalformedInput)
}