use std::cmp::Reverse;

use brk_error::{Error, Result};
use brk_types::{
    BlockInfoV1, Day1, Height, Pool, PoolBlockCounts, PoolBlockShares, PoolDetail, PoolDetailInfo,
    PoolHashrateEntry, PoolInfo, PoolSlug, PoolStats, PoolsSummary, StoredF64, StoredU64,
    TimePeriod, pools,
};
use vecdb::{AnyVec, ReadableVec, VecIndex};

use crate::Query;

/// 7-day lookback for share computation (matching mempool.space)
const LOOKBACK_DAYS: usize = 7;
/// Weekly sample interval (matching mempool.space's 604800s interval)
const SAMPLE_WEEKLY: usize = 7;

/// Pre-read shared data for hashrate computation.
struct HashrateSharedData {
    start_day: usize,
    end_day: usize,
    daily_hashrate: Vec<Option<StoredF64>>,
    first_heights: Vec<Height>,
}

impl Query {
    pub fn mining_pools(&self, time_period: TimePeriod) -> Result<PoolsSummary> {
        let computer = self.computer();
        let current_height = self.height();

        // No blocks indexed yet
        if computer.pools.pool.len() == 0 {
            return Ok(PoolsSummary {
                pools: vec![],
                block_count: 0,
                last_estimated_hashrate: 0,
                last_estimated_hashrate3d: 0,
                last_estimated_hashrate1w: 0,
            });
        }

        // Use timestamp-based lookback for accurate time boundaries
        let lookback = &computer.blocks.lookback;
        let start = match time_period {
            TimePeriod::Day => lookback._24h.collect_one(current_height),
            TimePeriod::ThreeDays => lookback._3d.collect_one(current_height),
            TimePeriod::Week => lookback._1w.collect_one(current_height),
            TimePeriod::Month => lookback._1m.collect_one(current_height),
            TimePeriod::ThreeMonths => lookback._3m.collect_one(current_height),
            TimePeriod::SixMonths => lookback._6m.collect_one(current_height),
            TimePeriod::Year => lookback._1y.collect_one(current_height),
            TimePeriod::TwoYears => lookback._2y.collect_one(current_height),
            TimePeriod::ThreeYears => lookback._3y.collect_one(current_height),
            TimePeriod::All => None,
        }
        .unwrap_or_default()
        .to_usize();

        let pools = pools();
        let mut pool_data: Vec<(&'static Pool, u64)> = Vec::new();

        // For each pool, get cumulative count at end and start, subtract to get range count
        for (pool_id, cumulative) in computer
            .pools
            .major
            .iter()
            .map(|(id, v)| (id, &v.blocks_mined.cumulative.height))
            .chain(
                computer
                    .pools
                    .minor
                    .iter()
                    .map(|(id, v)| (id, &v.blocks_mined.cumulative.height)),
            )
        {
            let count_at_end: u64 = *cumulative.collect_one(current_height).unwrap_or_default();

            let count_at_start: u64 = if start == 0 {
                0
            } else {
                *cumulative
                    .collect_one(Height::from(start - 1))
                    .unwrap_or_default()
            };

            let block_count = count_at_end.saturating_sub(count_at_start);

            if block_count > 0 {
                pool_data.push((pools.get(*pool_id), block_count));
            }
        }

        // Sort by block count descending
        pool_data.sort_by_key(|p| Reverse(p.1));

        let total_blocks: u64 = pool_data.iter().map(|(_, count)| count).sum();

        // Build stats with ranks
        let pool_stats: Vec<PoolStats> = pool_data
            .into_iter()
            .enumerate()
            .map(|(idx, (pool, block_count))| {
                let share = if total_blocks > 0 {
                    block_count as f64 / total_blocks as f64
                } else {
                    0.0
                };
                PoolStats::new(pool, block_count, (idx + 1) as u32, share)
            })
            .collect();

        let hashrate_at = |height: Height| -> u128 {
            let day = computer
                .indexes
                .height
                .day1
                .collect_one(height)
                .unwrap_or_default();
            computer
                .mining
                .hashrate
                .rate
                .base
                .day1
                .collect_one(day)
                .flatten()
                .map(|v| *v as u128)
                .unwrap_or(0)
        };

        let lookback = &computer.blocks.lookback;
        let last_estimated_hashrate = hashrate_at(current_height);
        let last_estimated_hashrate3d =
            hashrate_at(lookback._3d.collect_one(current_height).unwrap_or_default());
        let last_estimated_hashrate1w =
            hashrate_at(lookback._1w.collect_one(current_height).unwrap_or_default());

        Ok(PoolsSummary {
            pools: pool_stats,
            block_count: total_blocks,
            last_estimated_hashrate,
            last_estimated_hashrate3d,
            last_estimated_hashrate1w,
        })
    }

    pub fn all_pools(&self) -> Vec<PoolInfo> {
        pools().iter().map(PoolInfo::from).collect()
    }

    pub fn pool_detail(&self, slug: PoolSlug) -> Result<PoolDetail> {
        let computer = self.computer();
        let current_height = self.height();
        let end = current_height.to_usize();

        let pools_list = pools();
        let pool = pools_list.get(slug);

        // Get cumulative blocks for this pool (works for both major and minor)
        let cumulative = computer
            .pools
            .major
            .get(&slug)
            .map(|v| &v.blocks_mined.cumulative.height)
            .or_else(|| {
                computer
                    .pools
                    .minor
                    .get(&slug)
                    .map(|v| &v.blocks_mined.cumulative.height)
            })
            .ok_or_else(|| Error::NotFound("Pool data not found".into()))?;

        // Get total blocks (all time)
        let total_all: u64 = *cumulative.collect_one(current_height).unwrap_or_default();

        // Use timestamp-based lookback for accurate time boundaries
        let lookback = &computer.blocks.lookback;
        let start_24h = lookback
            ._24h
            .collect_one(current_height)
            .unwrap_or_default()
            .to_usize();
        let count_before_24h: u64 = if start_24h == 0 {
            0
        } else {
            *cumulative
                .collect_one(Height::from(start_24h - 1))
                .unwrap_or_default()
        };
        let total_24h = total_all.saturating_sub(count_before_24h);

        let start_1w = lookback
            ._1w
            .collect_one(current_height)
            .unwrap_or_default()
            .to_usize();
        let count_before_1w: u64 = if start_1w == 0 {
            0
        } else {
            *cumulative
                .collect_one(Height::from(start_1w - 1))
                .unwrap_or_default()
        };
        let total_1w = total_all.saturating_sub(count_before_1w);

        // Calculate total network blocks for share calculation
        let network_blocks_all = (end + 1) as u64;
        let network_blocks_24h = (end - start_24h + 1) as u64;
        let network_blocks_1w = (end - start_1w + 1) as u64;

        let share_all = if network_blocks_all > 0 {
            total_all as f64 / network_blocks_all as f64
        } else {
            0.0
        };
        let share_24h = if network_blocks_24h > 0 {
            total_24h as f64 / network_blocks_24h as f64
        } else {
            0.0
        };
        let share_1w = if network_blocks_1w > 0 {
            total_1w as f64 / network_blocks_1w as f64
        } else {
            0.0
        };

        Ok(PoolDetail {
            pool: PoolDetailInfo::from(pool),
            block_count: PoolBlockCounts {
                all: total_all,
                day: total_24h,
                week: total_1w,
            },
            block_share: PoolBlockShares {
                all: share_all,
                day: share_24h,
                week: share_1w,
            },
            estimated_hashrate: {
                let day = computer
                    .indexes
                    .height
                    .day1
                    .collect_one(current_height)
                    .unwrap_or_default();
                let network_hr = computer
                    .mining
                    .hashrate
                    .rate
                    .base
                    .day1
                    .collect_one(day)
                    .flatten()
                    .map(|v| *v as u128)
                    .unwrap_or(0);
                (share_24h * network_hr as f64) as u128
            },
            reported_hashrate: None,
            total_reward: computer
                .pools
                .major
                .get(&slug)
                .and_then(|v| v.rewards.cumulative.sats.height.collect_one(current_height)),
        })
    }

    pub fn pool_blocks(
        &self,
        slug: PoolSlug,
        start_height: Option<Height>,
    ) -> Result<Vec<BlockInfoV1>> {
        let computer = self.computer();
        let max_height = self.height().to_usize();
        let start = start_height.map(|h| h.to_usize()).unwrap_or(max_height);
        let end = start.min(computer.pools.pool.len().saturating_sub(1));

        const POOL_BLOCKS_LIMIT: usize = 100;

        let heights: Vec<usize> = computer
            .pools
            .pool_heights
            .read()
            .get(&slug)
            .map(|pool_heights| {
                let pos = pool_heights.partition_point(|h| h.to_usize() <= end);
                let start = pos.saturating_sub(POOL_BLOCKS_LIMIT);
                pool_heights[start..pos]
                    .iter()
                    .rev()
                    .map(|h| h.to_usize())
                    .collect()
            })
            .unwrap_or_default();

        // Group consecutive descending heights into ranges for batch reads
        let mut blocks = Vec::with_capacity(heights.len());
        let mut i = 0;
        while i < heights.len() {
            let hi = heights[i];
            while i + 1 < heights.len() && heights[i + 1] + 1 == heights[i] {
                i += 1;
            }
            if let Ok(mut v) = self.blocks_v1_range(heights[i], hi + 1) {
                blocks.append(&mut v);
            }
            i += 1;
        }

        Ok(blocks)
    }

    pub fn pool_hashrate(&self, slug: PoolSlug) -> Result<Vec<PoolHashrateEntry>> {
        let pool_name = pools().get(slug).name.to_string();
        let shared = self.hashrate_shared_data(0)?;
        let pool_cum = self.pool_daily_cumulative(slug, shared.start_day, shared.end_day)?;
        Ok(Self::compute_hashrate_entries(
            &shared,
            &pool_cum,
            &pool_name,
            SAMPLE_WEEKLY,
        ))
    }

    pub fn pools_hashrate(
        &self,
        time_period: Option<TimePeriod>,
    ) -> Result<Vec<PoolHashrateEntry>> {
        let start_height = match time_period {
            Some(tp) => {
                let lookback = &self.computer().blocks.lookback;
                let current_height = self.height();
                match tp {
                    TimePeriod::Day => lookback._24h.collect_one(current_height),
                    TimePeriod::ThreeDays => lookback._3d.collect_one(current_height),
                    TimePeriod::Week => lookback._1w.collect_one(current_height),
                    TimePeriod::Month => lookback._1m.collect_one(current_height),
                    TimePeriod::ThreeMonths => lookback._3m.collect_one(current_height),
                    TimePeriod::SixMonths => lookback._6m.collect_one(current_height),
                    TimePeriod::Year => lookback._1y.collect_one(current_height),
                    TimePeriod::TwoYears => lookback._2y.collect_one(current_height),
                    TimePeriod::ThreeYears => lookback._3y.collect_one(current_height),
                    TimePeriod::All => None,
                }
                .unwrap_or_default()
                .to_usize()
            }
            None => 0,
        };

        let shared = self.hashrate_shared_data(start_height)?;
        let pools_list = pools();
        let mut entries = Vec::new();

        for pool in pools_list.iter() {
            let Ok(pool_cum) =
                self.pool_daily_cumulative(pool.slug, shared.start_day, shared.end_day)
            else {
                continue;
            };
            entries.extend(Self::compute_hashrate_entries(
                &shared,
                &pool_cum,
                pool.name,
                SAMPLE_WEEKLY,
            ));
        }

        Ok(entries)
    }

    /// Shared data needed for hashrate computation (read once, reuse across pools).
    fn hashrate_shared_data(&self, start_height: usize) -> Result<HashrateSharedData> {
        let computer = self.computer();
        let current_height = self.height();
        let start_day = computer
            .indexes
            .height
            .day1
            .collect_one_at(start_height)
            .unwrap_or_default()
            .to_usize();
        let end_day = computer
            .indexes
            .height
            .day1
            .collect_one(current_height)
            .unwrap_or_default()
            .to_usize()
            + 1;
        let daily_hashrate = computer
            .mining
            .hashrate
            .rate
            .base
            .day1
            .collect_range_at(start_day, end_day);
        let first_heights = computer
            .indexes
            .day1
            .first_height
            .collect_range_at(start_day, end_day);

        Ok(HashrateSharedData {
            start_day,
            end_day,
            daily_hashrate,
            first_heights,
        })
    }

    /// Read daily cumulative blocks mined for a pool.
    fn pool_daily_cumulative(
        &self,
        slug: PoolSlug,
        start_day: usize,
        end_day: usize,
    ) -> Result<Vec<Option<StoredU64>>> {
        let computer = self.computer();
        computer
            .pools
            .major
            .get(&slug)
            .map(|v| {
                v.base
                    .blocks_mined
                    .cumulative
                    .day1
                    .collect_range_at(start_day, end_day)
            })
            .or_else(|| {
                computer.pools.minor.get(&slug).map(|v| {
                    v.blocks_mined
                        .cumulative
                        .day1
                        .collect_range_at(start_day, end_day)
                })
            })
            .ok_or_else(|| Error::NotFound("Pool not found".into()))
    }

    /// Compute hashrate entries from daily cumulative blocks + shared data.
    /// Uses 7-day windowed share: pool_blocks_in_week / total_blocks_in_week.
    fn compute_hashrate_entries(
        shared: &HashrateSharedData,
        pool_cum: &[Option<StoredU64>],
        pool_name: &str,
        sample_days: usize,
    ) -> Vec<PoolHashrateEntry> {
        let total = pool_cum.len();
        if total <= LOOKBACK_DAYS {
            return vec![];
        }

        let mut entries = Vec::new();
        let mut i = LOOKBACK_DAYS;
        while i < total {
            if let (Some(cum_now), Some(cum_prev)) = (pool_cum[i], pool_cum[i - LOOKBACK_DAYS]) {
                let pool_blocks = (*cum_now).saturating_sub(*cum_prev);
                if pool_blocks > 0 {
                    let h_now = shared.first_heights[i].to_usize();
                    let h_prev = shared.first_heights[i - LOOKBACK_DAYS].to_usize();
                    let total_blocks = h_now.saturating_sub(h_prev);

                    if total_blocks > 0
                        && let Some(hr) = shared.daily_hashrate[i].as_ref()
                    {
                        let network_hr = **hr;
                        let share = pool_blocks as f64 / total_blocks as f64;
                        let day = Day1::from(shared.start_day + i);
                        entries.push(PoolHashrateEntry {
                            timestamp: day.to_timestamp(),
                            avg_hashrate: (network_hr * share) as u128,
                            share,
                            pool_name: pool_name.to_string(),
                        });
                    }
                }
            }
            i += sample_days;
        }

        entries
    }
}