use std::sync::LazyLock;

use brk_error::{Error, Result};
use brk_traversable::TreeNode;
use brk_types::{
    BlockHashPrefix, CacheClass, Date, DetailedSeriesCount, Epoch, Format, Halving, Height, Index,
    IndexInfo, LegacyValue, Limit, Output, OutputLegacy, PaginatedSeries, Pagination, RangeIndex,
    RangeMap, SearchQuery, SeriesData, SeriesInfo, SeriesName, SeriesOutput, SeriesOutputLegacy,
    SeriesSelection, Timestamp, Version,
};
use parking_lot::RwLock;
use vecdb::{AnyExportableVec, ReadableVec};

use crate::Query;

/// Monotonic block timestamps → height. Lazily extended as new blocks are indexed.
static HEIGHT_BY_MONOTONIC_TIMESTAMP: LazyLock<RwLock<RangeMap<Timestamp, Height>>> =
    LazyLock::new(|| RwLock::new(RangeMap::default()));

/// Estimated bytes per column header
const CSV_HEADER_BYTES_PER_COL: usize = 10;
/// Estimated bytes per cell value
const CSV_CELL_BYTES: usize = 15;
/// Estimated bytes per JSON cell value
const JSON_CELL_BYTES: usize = 12;

impl Query {
    pub fn search_series(&self, query: &SearchQuery) -> Vec<&'static str> {
        self.vecs().matches(&query.q, query.limit)
    }

    /// Returns the error for a missing series: `SeriesUnsupportedIndex` if the name
    /// exists at other indexes, else `SeriesNotFound` with fuzzy-match suggestions.
    pub fn series_not_found_error(&self, series: &SeriesName) -> Error {
        if let Some(indexes) = self.vecs().series_to_indexes(series) {
            let supported = indexes
                .iter()
                .map(|i| format!("/api/series/{series}/{}", i.name()))
                .collect::<Vec<_>>()
                .join(", ");
            return Error::SeriesUnsupportedIndex {
                series: brk_error::truncate_series_name(series.to_string()),
                supported,
            };
        }

        let matches = self.vecs().matches(series, Limit::DEFAULT);
        let total_matches = matches.len();
        let suggestions = matches.into_iter().take(3).collect();
        Error::SeriesNotFound(brk_error::SeriesNotFound::new(
            series.to_string(),
            suggestions,
            total_matches,
        ))
    }

    pub(crate) fn columns_to_csv(
        columns: &[&dyn AnyExportableVec],
        start: usize,
        end: usize,
    ) -> Result<String> {
        if columns.is_empty() {
            return Ok(String::new());
        }

        let num_cols = columns.len();
        let mut csv = String::with_capacity(num_cols * CSV_HEADER_BYTES_PER_COL);
        for (i, col) in columns.iter().enumerate() {
            if i > 0 {
                csv.push(',');
            }
            csv.push_str(col.name());
        }
        csv.push('\n');

        // Stream a single column without materializing Vec<T>.
        if num_cols == 1 {
            columns[0].write_csv_column(Some(start), Some(end), &mut csv)?;
            return Ok(csv);
        }

        let from = Some(start as i64);
        let to = Some(end as i64);
        let num_rows = columns[0].range_count(from, to);
        csv.reserve(num_rows * num_cols * CSV_CELL_BYTES);

        let mut writers: Vec<_> = columns
            .iter()
            .map(|col| col.create_writer(from, to))
            .collect();

        for _ in 0..num_rows {
            for (i, writer) in writers.iter_mut().enumerate() {
                if i > 0 {
                    csv.push(',');
                }
                writer.write_next(&mut csv)?;
            }
            csv.push('\n');
        }

        Ok(csv)
    }

    fn get_vec(&self, series: &SeriesName, index: Index) -> Result<&'static dyn AnyExportableVec> {
        self.vecs()
            .get(series, index)
            .ok_or_else(|| self.series_not_found_error(series))
    }

    /// Returns the latest value for a single series as a JSON value.
    pub fn latest(&self, series: &SeriesName, index: Index) -> Result<serde_json::Value> {
        self.get_vec(series, index)?
            .last_json_value()
            .ok_or(Error::NoData)
    }

    /// Returns the length (total data points) for a single series.
    pub fn len(&self, series: &SeriesName, index: Index) -> Result<usize> {
        Ok(self.get_vec(series, index)?.len())
    }

    /// Returns the version for a single series.
    pub fn version(&self, series: &SeriesName, index: Index) -> Result<Version> {
        Ok(self.get_vec(series, index)?.version())
    }

    /// Search for vecs matching the given series and index.
    /// Returns error if no series requested or any requested series is not found.
    pub fn search(&self, params: &SeriesSelection) -> Result<Vec<&'static dyn AnyExportableVec>> {
        if params.series.is_empty() {
            return Err(Error::NoSeries);
        }
        params
            .series
            .iter()
            .map(|s| self.get_vec(s, params.index))
            .collect()
    }

    /// Calculate total weight of the vecs for the given range.
    pub fn weight(vecs: &[&dyn AnyExportableVec], from: Option<i64>, to: Option<i64>) -> usize {
        vecs.iter().map(|v| v.range_weight(from, to)).sum()
    }

    /// Resolve query metadata without formatting (cheap).
    /// Use with `format` for lazy formatting after ETag check.
    pub fn resolve(&self, params: SeriesSelection, max_weight: usize) -> Result<ResolvedQuery> {
        let vecs = self.search(&params)?;

        let total = vecs.iter().map(|v| v.len()).min().unwrap_or(0);
        let version: Version = vecs.iter().map(|v| v.version()).sum();
        let index = params.index;

        let resolve_bound = |ri: RangeIndex, fallback: usize| -> Result<usize> {
            let i = self.range_index_to_i64(ri, index)?;
            Ok(vecs
                .iter()
                .map(|v| v.i64_to_usize(i))
                .min()
                .unwrap_or(fallback))
        };

        let start = match params.start() {
            Some(ri) => resolve_bound(ri, 0)?,
            None => 0,
        };

        let end = match params.end() {
            Some(ri) => resolve_bound(ri, total)?,
            None => params
                .limit()
                .map(|l| start.saturating_add(*l).min(total))
                .unwrap_or(total),
        };

        let end = end.max(start);
        let weight = Self::weight(&vecs, Some(start as i64), Some(end as i64));
        if weight > max_weight {
            return Err(Error::WeightExceeded {
                requested: weight,
                max: max_weight,
            });
        }

        // Snapshot tip-derived state together so the historical-branch ETag stays
        // self-consistent: tip_height and hash_prefix both reflect the safe-bound
        // tip, and stable_count is computed from tip_height.
        let tip_height = self.height();
        let hash_prefix = self.tip_hash_prefix();
        let stable_count = self.stable_count(params.index, total, tip_height);

        Ok(ResolvedQuery {
            vecs,
            format: params.format(),
            index: params.index,
            version,
            total,
            start,
            end,
            hash_prefix,
            stable_count,
        })
    }

    /// Count of leading entries provably immutable across a 6-block reorg, used
    /// to gate the historical-branch series ETag.
    ///
    /// - Bucketed indexes: `total - margin`.
    /// - Entity indexes: `first_X_index[tip_height - 6]`, falling back to 0 if
    ///   the tip is shallower than 6 blocks. Clamped to `total` so a query
    ///   whose vecs are shorter than the entity-type's own count never marks
    ///   its live tail as stable.
    /// - Mutable (Funded/Empty addr): `None`. No immutable region exists, so
    ///   the caller must use the tip-bound ETag for every range.
    pub fn stable_count(&self, index: Index, total: usize, tip_height: Height) -> Option<usize> {
        match index.cache_class() {
            CacheClass::Bucket { margin } => Some(total.saturating_sub(margin)),
            CacheClass::Entity => {
                let h = Height::from((*tip_height).saturating_sub(6));
                Some(self.entity_index_at(index, h).unwrap_or(0).min(total))
            }
            CacheClass::Mutable => None,
        }
    }

    fn entity_index_at(&self, index: Index, h: Height) -> Option<usize> {
        let v = &self.indexer().vecs;
        match index {
            Index::TxIndex => v
                .transactions
                .first_tx_index
                .collect_one(h)
                .map(usize::from),
            Index::TxInIndex => v.inputs.first_txin_index.collect_one(h).map(usize::from),
            Index::TxOutIndex => v.outputs.first_txout_index.collect_one(h).map(usize::from),
            Index::EmptyOutputIndex => v.scripts.empty.first_index.collect_one(h).map(usize::from),
            Index::OpReturnIndex => v.op_return.first_index.collect_one(h).map(usize::from),
            Index::P2MSOutputIndex => v.scripts.p2ms.first_index.collect_one(h).map(usize::from),
            Index::UnknownOutputIndex => v
                .scripts
                .unknown
                .first_index
                .collect_one(h)
                .map(usize::from),
            Index::P2AAddrIndex => v.addrs.p2a.first_index.collect_one(h).map(usize::from),
            Index::P2PK33AddrIndex => v.addrs.p2pk33.first_index.collect_one(h).map(usize::from),
            Index::P2PK65AddrIndex => v.addrs.p2pk65.first_index.collect_one(h).map(usize::from),
            Index::P2PKHAddrIndex => v.addrs.p2pkh.first_index.collect_one(h).map(usize::from),
            Index::P2SHAddrIndex => v.addrs.p2sh.first_index.collect_one(h).map(usize::from),
            Index::P2TRAddrIndex => v.addrs.p2tr.first_index.collect_one(h).map(usize::from),
            Index::P2WPKHAddrIndex => v.addrs.p2wpkh.first_index.collect_one(h).map(usize::from),
            Index::P2WSHAddrIndex => v.addrs.p2wsh.first_index.collect_one(h).map(usize::from),
            _ => unreachable!("entity_index_at called for non-Entity Index: {index:?}"),
        }
    }

    /// Format a resolved query (expensive).
    /// Call after ETag/cache checks to avoid unnecessary work.
    pub fn format(&self, resolved: ResolvedQuery) -> Result<SeriesOutput> {
        let ResolvedQuery {
            vecs,
            format,
            index,
            version,
            total,
            start,
            end,
            ..
        } = resolved;

        let output = match format {
            Format::CSV => Output::CSV(Self::columns_to_csv(&vecs, start, end)?),
            Format::JSON => {
                let count = end.saturating_sub(start);
                Output::Json(Self::write_json_array(&vecs, count, 256, |v, buf| {
                    SeriesData::serialize(v, index, start, end, buf)
                })?)
            }
        };

        Ok(SeriesOutput {
            output,
            version,
            total,
            start,
            end,
        })
    }

    /// Format a resolved query as raw data (just the JSON values, no SeriesData wrapper).
    /// Single vec → `[v1,v2,...]`. Multi-vec → `[[v1,v2],[v3,v4],...]`.
    /// CSV output is identical to `format` (no wrapper distinction for CSV).
    pub fn format_raw(&self, resolved: ResolvedQuery) -> Result<SeriesOutput> {
        if resolved.format == Format::CSV {
            return self.format(resolved);
        }

        let ResolvedQuery {
            vecs,
            version,
            total,
            start,
            end,
            ..
        } = resolved;

        let count = end.saturating_sub(start);
        let buf = Self::write_json_array(&vecs, count, 2, |v, buf| {
            v.write_json(Some(start), Some(end), buf)
        })?;

        Ok(SeriesOutput {
            output: Output::Json(buf),
            version,
            total,
            start,
            end,
        })
    }

    fn write_json_array(
        vecs: &[&dyn AnyExportableVec],
        cell_count: usize,
        wrapper_overhead: usize,
        mut write_one: impl FnMut(&dyn AnyExportableVec, &mut Vec<u8>) -> vecdb::Result<()>,
    ) -> Result<Vec<u8>> {
        let multi = vecs.len() > 1;
        let mut buf =
            Vec::with_capacity(cell_count * JSON_CELL_BYTES * vecs.len() + wrapper_overhead);
        if multi {
            buf.push(b'[');
        }
        for (i, vec) in vecs.iter().enumerate() {
            if i > 0 {
                buf.push(b',');
            }
            write_one(*vec, &mut buf)?;
        }
        if multi {
            buf.push(b']');
        }
        Ok(buf)
    }

    pub fn series_count(&self) -> DetailedSeriesCount {
        DetailedSeriesCount {
            total: self.vecs().counts.clone(),
            by_db: self.vecs().counts_by_db.clone(),
        }
    }

    pub fn indexes(&self) -> &'static [IndexInfo] {
        &self.vecs().indexes
    }

    pub fn series_list(&self, pagination: Pagination) -> PaginatedSeries {
        self.vecs().series(pagination)
    }

    pub fn series_catalog(&self) -> &'static TreeNode {
        self.vecs().catalog()
    }

    pub fn series_info(&self, series: &SeriesName) -> Option<SeriesInfo> {
        self.vecs().series_info(series)
    }

    /// Resolve a RangeIndex to an i64 offset for the given index type.
    fn range_index_to_i64(&self, ri: RangeIndex, index: Index) -> Result<i64> {
        match ri {
            RangeIndex::Int(i) => Ok(i),
            RangeIndex::Date(date) => self.date_to_i64(date, index),
            RangeIndex::Timestamp(ts) => self.timestamp_to_i64(ts, index),
        }
    }

    fn date_to_i64(&self, date: Date, index: Index) -> Result<i64> {
        if let Some(idx) = index.date_to_index(date) {
            return Ok(idx as i64);
        }
        self.timestamp_to_i64(Timestamp::from(date), index)
    }

    fn timestamp_to_i64(&self, ts: Timestamp, index: Index) -> Result<i64> {
        if let Some(idx) = index.timestamp_to_index(ts) {
            return Ok(idx as i64);
        }
        let height = Height::from(self.height_for_timestamp(ts));
        match index {
            Index::Height => Ok(usize::from(height) as i64),
            Index::Epoch => Ok(usize::from(Epoch::from(height)) as i64),
            Index::Halving => Ok(usize::from(Halving::from(height)) as i64),
            _ => Err(Error::Parse(format!(
                "date/timestamp ranges not supported for index '{index}'"
            ))),
        }
    }

    /// Find the first block height at or after a given timestamp.
    /// O(log n) binary search. Lazily rebuilt as new blocks arrive.
    fn height_for_timestamp(&self, ts: Timestamp) -> usize {
        let current_height: usize = self.height().into();
        let lookup = |map: &RangeMap<Timestamp, Height>| {
            map.ceil(ts).map(usize::from).unwrap_or(current_height)
        };

        {
            let map = HEIGHT_BY_MONOTONIC_TIMESTAMP.read();
            if map.len() > current_height {
                return lookup(&map);
            }
        }

        let mut map = HEIGHT_BY_MONOTONIC_TIMESTAMP.write();
        if map.len() <= current_height {
            *map = RangeMap::from(self.computer().indexes.timestamp.monotonic.collect());
        }
        lookup(&map)
    }

    /// Deprecated - format a resolved query as legacy output (expensive).
    pub fn format_legacy(&self, resolved: ResolvedQuery) -> Result<SeriesOutputLegacy> {
        let ResolvedQuery {
            vecs,
            format,
            version,
            total,
            start,
            end,
            ..
        } = resolved;

        if vecs.is_empty() {
            return Ok(SeriesOutputLegacy {
                output: OutputLegacy::default(format),
                version: Version::ZERO,
                total: 0,
                start: 0,
                end: 0,
            });
        }

        let from = Some(start as i64);
        let to = Some(end as i64);

        let output = match format {
            Format::CSV => OutputLegacy::CSV(Self::columns_to_csv(&vecs, start, end)?),
            Format::JSON => {
                if vecs.len() == 1 {
                    let col = vecs[0];
                    let count = col.range_count(from, to);
                    let mut buf = Vec::new();
                    if count == 1 {
                        col.write_json_value(Some(start), &mut buf)?;
                        OutputLegacy::Json(LegacyValue::Value(buf))
                    } else {
                        col.write_json(Some(start), Some(end), &mut buf)?;
                        OutputLegacy::Json(LegacyValue::List(buf))
                    }
                } else {
                    let mut values = Vec::with_capacity(vecs.len());
                    for vec in &vecs {
                        let mut buf = Vec::new();
                        vec.write_json(Some(start), Some(end), &mut buf)?;
                        values.push(buf);
                    }
                    OutputLegacy::Json(LegacyValue::Matrix(values))
                }
            }
        };

        Ok(SeriesOutputLegacy {
            output,
            version,
            total,
            start,
            end,
        })
    }
}

/// A resolved series query ready for formatting.
/// Carries the vecs plus the metadata callers need to derive an etag or cache
/// policy. `stable_count` is `None` for indexes whose entries can mutate
/// retroactively (Funded/Empty addr).
pub struct ResolvedQuery {
    pub vecs: Vec<&'static dyn AnyExportableVec>,
    pub format: Format,
    pub index: Index,
    pub version: Version,
    pub total: usize,
    pub start: usize,
    pub end: usize,
    pub hash_prefix: BlockHashPrefix,
    pub stable_count: Option<usize>,
}

impl ResolvedQuery {
    pub fn csv_filename(&self) -> String {
        let names: Vec<_> = self.vecs.iter().map(|v| v.name()).collect();
        format!("{}-{}.csv", names.join("_"), self.index)
    }
}
