use std::collections::{BTreeMap, HashMap};
use std::fs;
use std::path::Path;

use chrono::NaiveDate;
use serde::{Deserialize, Serialize};
use thiserror::Error;

use crate::calendar::TradingCalendar;
use crate::instrument::Instrument;

mod date_format {
    use chrono::NaiveDate;
    use serde::{self, Deserialize, Deserializer, Serializer};

    const FORMAT: &str = "%Y-%m-%d";

    pub fn serialize<S>(date: &NaiveDate, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        serializer.serialize_str(&date.format(FORMAT).to_string())
    }

    pub fn deserialize<'de, D>(deserializer: D) -> Result<NaiveDate, D::Error>
    where
        D: Deserializer<'de>,
    {
        let text = String::deserialize(deserializer)?;
        NaiveDate::parse_from_str(&text, FORMAT).map_err(serde::de::Error::custom)
    }
}

#[derive(Debug, Error)]
pub enum DataSetError {
    #[error("failed to read file {path}: {source}")]
    Io {
        path: String,
        #[source]
        source: std::io::Error,
    },
    #[error("invalid csv row in {path} at line {line}: {message}")]
    InvalidRow {
        path: String,
        line: usize,
        message: String,
    },
    #[error("benchmark file contains multiple benchmark codes")]
    MultipleBenchmarks,
    #[error("missing data for {kind} on {date} / {symbol}")]
    MissingSnapshot {
        kind: &'static str,
        date: NaiveDate,
        symbol: String,
    },
    #[error("benchmark snapshot missing for {date}")]
    MissingBenchmark { date: NaiveDate },
}

#[derive(Debug, Clone, Copy)]
pub enum PriceField {
    Open,
    Close,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DailyMarketSnapshot {
    #[serde(with = "date_format")]
    pub date: NaiveDate,
    pub symbol: String,
    pub open: f64,
    pub high: f64,
    pub low: f64,
    pub close: f64,
    pub prev_close: f64,
    pub volume: u64,
    pub paused: bool,
    pub upper_limit: f64,
    pub lower_limit: f64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DailyFactorSnapshot {
    #[serde(with = "date_format")]
    pub date: NaiveDate,
    pub symbol: String,
    pub market_cap_bn: f64,
    pub free_float_cap_bn: f64,
    pub pe_ttm: f64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BenchmarkSnapshot {
    #[serde(with = "date_format")]
    pub date: NaiveDate,
    pub benchmark: String,
    pub open: f64,
    pub close: f64,
    pub prev_close: f64,
    pub volume: u64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CandidateEligibility {
    #[serde(with = "date_format")]
    pub date: NaiveDate,
    pub symbol: String,
    pub is_st: bool,
    pub is_new_listing: bool,
    pub is_paused: bool,
    pub allow_buy: bool,
    pub allow_sell: bool,
}

impl CandidateEligibility {
    pub fn eligible_for_selection(&self) -> bool {
        !self.is_st && !self.is_new_listing && !self.is_paused && self.allow_buy && self.allow_sell
    }
}

#[derive(Debug, Clone)]
pub struct DataSet {
    instruments: HashMap<String, Instrument>,
    calendar: TradingCalendar,
    market_by_date: BTreeMap<NaiveDate, Vec<DailyMarketSnapshot>>,
    market_index: HashMap<(NaiveDate, String), DailyMarketSnapshot>,
    factor_by_date: BTreeMap<NaiveDate, Vec<DailyFactorSnapshot>>,
    factor_index: HashMap<(NaiveDate, String), DailyFactorSnapshot>,
    candidate_by_date: BTreeMap<NaiveDate, Vec<CandidateEligibility>>,
    candidate_index: HashMap<(NaiveDate, String), CandidateEligibility>,
    benchmark_by_date: BTreeMap<NaiveDate, BenchmarkSnapshot>,
    benchmark_code: String,
}

impl DataSet {
    pub fn from_csv_dir(path: &Path) -> Result<Self, DataSetError> {
        let instruments = read_instruments(&path.join("instruments.csv"))?;
        let market = read_market(&path.join("market.csv"))?;
        let factors = read_factors(&path.join("factors.csv"))?;
        let candidates = read_candidates(&path.join("candidate_flags.csv"))?;
        let benchmarks = read_benchmarks(&path.join("benchmark.csv"))?;

        let benchmark_code = collect_benchmark_code(&benchmarks)?;
        let calendar = TradingCalendar::new(benchmarks.iter().map(|item| item.date).collect());

        let instruments = instruments
            .into_iter()
            .map(|instrument| (instrument.symbol.clone(), instrument))
            .collect::<HashMap<_, _>>();

        let market_by_date = group_by_date(market.clone(), |item| item.date);
        let market_index = market
            .into_iter()
            .map(|item| ((item.date, item.symbol.clone()), item))
            .collect::<HashMap<_, _>>();

        let factor_by_date = group_by_date(factors.clone(), |item| item.date);
        let factor_index = factors
            .into_iter()
            .map(|item| ((item.date, item.symbol.clone()), item))
            .collect::<HashMap<_, _>>();

        let candidate_by_date = group_by_date(candidates.clone(), |item| item.date);
        let candidate_index = candidates
            .into_iter()
            .map(|item| ((item.date, item.symbol.clone()), item))
            .collect::<HashMap<_, _>>();

        let benchmark_by_date = benchmarks
            .into_iter()
            .map(|item| (item.date, item))
            .collect::<BTreeMap<_, _>>();

        Ok(Self {
            instruments,
            calendar,
            market_by_date,
            market_index,
            factor_by_date,
            factor_index,
            candidate_by_date,
            candidate_index,
            benchmark_by_date,
            benchmark_code,
        })
    }

    pub fn calendar(&self) -> &TradingCalendar {
        &self.calendar
    }

    pub fn benchmark_code(&self) -> &str {
        &self.benchmark_code
    }

    pub fn instruments(&self) -> &HashMap<String, Instrument> {
        &self.instruments
    }

    pub fn market(&self, date: NaiveDate, symbol: &str) -> Option<&DailyMarketSnapshot> {
        self.market_index.get(&(date, symbol.to_string()))
    }

    pub fn factor(&self, date: NaiveDate, symbol: &str) -> Option<&DailyFactorSnapshot> {
        self.factor_index.get(&(date, symbol.to_string()))
    }

    pub fn candidate(&self, date: NaiveDate, symbol: &str) -> Option<&CandidateEligibility> {
        self.candidate_index.get(&(date, symbol.to_string()))
    }

    pub fn benchmark(&self, date: NaiveDate) -> Option<&BenchmarkSnapshot> {
        self.benchmark_by_date.get(&date)
    }

    pub fn benchmark_series(&self) -> Vec<BenchmarkSnapshot> {
        self.benchmark_by_date.values().cloned().collect()
    }

    pub fn price(&self, date: NaiveDate, symbol: &str, field: PriceField) -> Option<f64> {
        let snapshot = self.market(date, symbol)?;
        Some(match field {
            PriceField::Open => snapshot.open,
            PriceField::Close => snapshot.close,
        })
    }

    pub fn factor_snapshots_on(&self, date: NaiveDate) -> Vec<&DailyFactorSnapshot> {
        self.factor_by_date
            .get(&date)
            .map(|rows| rows.iter().collect())
            .unwrap_or_default()
    }

    pub fn market_snapshots_on(&self, date: NaiveDate) -> Vec<&DailyMarketSnapshot> {
        self.market_by_date
            .get(&date)
            .map(|rows| rows.iter().collect())
            .unwrap_or_default()
    }

    pub fn candidate_snapshots_on(&self, date: NaiveDate) -> Vec<&CandidateEligibility> {
        self.candidate_by_date
            .get(&date)
            .map(|rows| rows.iter().collect())
            .unwrap_or_default()
    }

    pub fn benchmark_closes_up_to(&self, date: NaiveDate, lookback: usize) -> Vec<f64> {
        self.calendar
            .trailing_days(date, lookback)
            .into_iter()
            .filter_map(|day| self.benchmark(day).map(|row| row.close))
            .collect()
    }

    pub fn require_market(
        &self,
        date: NaiveDate,
        symbol: &str,
    ) -> Result<&DailyMarketSnapshot, DataSetError> {
        self.market(date, symbol).ok_or_else(|| DataSetError::MissingSnapshot {
            kind: "market",
            date,
            symbol: symbol.to_string(),
        })
    }

    pub fn require_candidate(
        &self,
        date: NaiveDate,
        symbol: &str,
    ) -> Result<&CandidateEligibility, DataSetError> {
        self.candidate(date, symbol)
            .ok_or_else(|| DataSetError::MissingSnapshot {
                kind: "candidate",
                date,
                symbol: symbol.to_string(),
            })
    }
}

fn read_instruments(path: &Path) -> Result<Vec<Instrument>, DataSetError> {
    let rows = read_rows(path)?;
    let mut instruments = Vec::new();
    for row in rows {
        instruments.push(Instrument {
            symbol: row.get(0)?.to_string(),
            name: row.get(1)?.to_string(),
            board: row.get(2)?.to_string(),
        });
    }
    Ok(instruments)
}

fn read_market(path: &Path) -> Result<Vec<DailyMarketSnapshot>, DataSetError> {
    let rows = read_rows(path)?;
    let mut snapshots = Vec::new();
    for row in rows {
        let prev_close = row.parse_f64(6)?;
        snapshots.push(DailyMarketSnapshot {
            date: row.parse_date(0)?,
            symbol: row.get(1)?.to_string(),
            open: row.parse_f64(2)?,
            high: row.parse_f64(3)?,
            low: row.parse_f64(4)?,
            close: row.parse_f64(5)?,
            prev_close,
            volume: row.parse_u64(7)?,
            paused: row.parse_bool(8)?,
            upper_limit: round2(prev_close * 1.10),
            lower_limit: round2(prev_close * 0.90),
        });
    }
    Ok(snapshots)
}

fn read_factors(path: &Path) -> Result<Vec<DailyFactorSnapshot>, DataSetError> {
    let rows = read_rows(path)?;
    let mut snapshots = Vec::new();
    for row in rows {
        snapshots.push(DailyFactorSnapshot {
            date: row.parse_date(0)?,
            symbol: row.get(1)?.to_string(),
            market_cap_bn: row.parse_f64(2)?,
            free_float_cap_bn: row.parse_f64(3)?,
            pe_ttm: row.parse_f64(4)?,
        });
    }
    Ok(snapshots)
}

fn read_candidates(path: &Path) -> Result<Vec<CandidateEligibility>, DataSetError> {
    let rows = read_rows(path)?;
    let mut snapshots = Vec::new();
    for row in rows {
        snapshots.push(CandidateEligibility {
            date: row.parse_date(0)?,
            symbol: row.get(1)?.to_string(),
            is_st: row.parse_bool(2)?,
            is_new_listing: row.parse_bool(3)?,
            is_paused: row.parse_bool(4)?,
            allow_buy: row.parse_bool(5)?,
            allow_sell: row.parse_bool(6)?,
        });
    }
    Ok(snapshots)
}

fn read_benchmarks(path: &Path) -> Result<Vec<BenchmarkSnapshot>, DataSetError> {
    let rows = read_rows(path)?;
    let mut snapshots = Vec::new();
    for row in rows {
        snapshots.push(BenchmarkSnapshot {
            date: row.parse_date(0)?,
            benchmark: row.get(1)?.to_string(),
            open: row.parse_f64(2)?,
            close: row.parse_f64(3)?,
            prev_close: row.parse_f64(4)?,
            volume: row.parse_u64(5)?,
        });
    }
    Ok(snapshots)
}

struct CsvRow {
    path: String,
    line: usize,
    fields: Vec<String>,
}

impl CsvRow {
    fn get(&self, index: usize) -> Result<&str, DataSetError> {
        self.fields.get(index).map(String::as_str).ok_or_else(|| DataSetError::InvalidRow {
            path: self.path.clone(),
            line: self.line,
            message: format!("missing column {index}"),
        })
    }

    fn parse_date(&self, index: usize) -> Result<NaiveDate, DataSetError> {
        NaiveDate::parse_from_str(self.get(index)?, "%Y-%m-%d").map_err(|err| DataSetError::InvalidRow {
            path: self.path.clone(),
            line: self.line,
            message: format!("invalid date: {err}"),
        })
    }

    fn parse_f64(&self, index: usize) -> Result<f64, DataSetError> {
        self.get(index)?
            .parse::<f64>()
            .map_err(|err| DataSetError::InvalidRow {
                path: self.path.clone(),
                line: self.line,
                message: format!("invalid f64: {err}"),
            })
    }

    fn parse_u64(&self, index: usize) -> Result<u64, DataSetError> {
        self.get(index)?
            .parse::<u64>()
            .map_err(|err| DataSetError::InvalidRow {
                path: self.path.clone(),
                line: self.line,
                message: format!("invalid u64: {err}"),
            })
    }

    fn parse_bool(&self, index: usize) -> Result<bool, DataSetError> {
        self.get(index)?
            .parse::<bool>()
            .map_err(|err| DataSetError::InvalidRow {
                path: self.path.clone(),
                line: self.line,
                message: format!("invalid bool: {err}"),
            })
    }
}

fn read_rows(path: &Path) -> Result<Vec<CsvRow>, DataSetError> {
    let content = fs::read_to_string(path).map_err(|source| DataSetError::Io {
        path: path.display().to_string(),
        source,
    })?;

    let mut rows = Vec::new();
    for (line_idx, line) in content.lines().enumerate() {
        let line_no = line_idx + 1;
        if line_no == 1 || line.trim().is_empty() {
            continue;
        }

        rows.push(CsvRow {
            path: path.display().to_string(),
            line: line_no,
            fields: line.split(',').map(|field| field.trim().to_string()).collect(),
        });
    }

    Ok(rows)
}

fn group_by_date<T, F>(rows: Vec<T>, mut date_of: F) -> BTreeMap<NaiveDate, Vec<T>>
where
    F: FnMut(&T) -> NaiveDate,
{
    let mut grouped = BTreeMap::<NaiveDate, Vec<T>>::new();
    for row in rows {
        grouped.entry(date_of(&row)).or_default().push(row);
    }
    grouped
}

fn collect_benchmark_code(benchmarks: &[BenchmarkSnapshot]) -> Result<String, DataSetError> {
    let mut codes = benchmarks
        .iter()
        .map(|row| row.benchmark.clone())
        .collect::<Vec<_>>();
    codes.sort_unstable();
    codes.dedup();

    if codes.len() == 1 {
        Ok(codes.remove(0))
    } else {
        Err(DataSetError::MultipleBenchmarks)
    }
}

fn round2(value: f64) -> f64 {
    (value * 100.0).round() / 100.0
}