//! Contains the final aggregation tree.
//! This tree can be converted via the `into()` method from `IntermediateAggregationResults`.
//! This conversion computes the final result. For example: The intermediate result contains
//! intermediate average results, which is the sum and the number of values. The actual average is
//! calculated on the step from intermediate to final aggregation result tree.

use std::collections::HashMap;

use fnv::FnvHashMap;
use serde::{Deserialize, Serialize};

use super::agg_req::BucketAggregationInternal;
use super::bucket::GetDocCount;
use super::intermediate_agg_result::{IntermediateBucketResult, IntermediateMetricResult};
use super::metric::{SingleMetricResult, Stats};
use super::Key;
use crate::TantivyError;

#[derive(Clone, Default, Debug, PartialEq, Serialize, Deserialize)]
/// The final aggegation result.
pub struct AggregationResults(pub HashMap<String, AggregationResult>);

impl AggregationResults {
    pub(crate) fn get_value_from_aggregation(
        &self,
        name: &str,
        agg_property: &str,
    ) -> crate::Result<Option<f64>> {
        if let Some(agg) = self.0.get(name) {
            agg.get_value_from_aggregation(name, agg_property)
        } else {
            // Validation is be done during request parsing, so we can't reach this state.
            Err(TantivyError::InternalError(format!(
                "Can't find aggregation {:?} in sub_aggregations",
                name
            )))
        }
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(untagged)]
/// An aggregation is either a bucket or a metric.
pub enum AggregationResult {
    /// Bucket result variant.
    BucketResult(BucketResult),
    /// Metric result variant.
    MetricResult(MetricResult),
}

impl AggregationResult {
    pub(crate) fn get_value_from_aggregation(
        &self,
        _name: &str,
        agg_property: &str,
    ) -> crate::Result<Option<f64>> {
        match self {
            AggregationResult::BucketResult(_bucket) => Err(TantivyError::InternalError(
                "Tried to retrieve value from bucket aggregation. This is not supported and \
                 should not happen during collection phase, but should be caught during validation"
                    .to_string(),
            )),
            AggregationResult::MetricResult(metric) => metric.get_value(agg_property),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(untagged)]
/// MetricResult
pub enum MetricResult {
    /// Average metric result.
    Average(SingleMetricResult),
    /// Stats metric result.
    Stats(Stats),
}

impl MetricResult {
    fn get_value(&self, agg_property: &str) -> crate::Result<Option<f64>> {
        match self {
            MetricResult::Average(avg) => Ok(avg.value),
            MetricResult::Stats(stats) => stats.get_value(agg_property),
        }
    }
}
impl From<IntermediateMetricResult> for MetricResult {
    fn from(metric: IntermediateMetricResult) -> Self {
        match metric {
            IntermediateMetricResult::Average(avg_data) => {
                MetricResult::Average(avg_data.finalize().into())
            }
            IntermediateMetricResult::Stats(intermediate_stats) => {
                MetricResult::Stats(intermediate_stats.finalize())
            }
        }
    }
}

/// BucketEntry holds bucket aggregation result types.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(untagged)]
pub enum BucketResult {
    /// This is the range entry for a bucket, which contains a key, count, from, to, and optionally
    /// sub_aggregations.
    Range {
        /// The range buckets sorted by range.
        buckets: BucketEntries<RangeBucketEntry>,
    },
    /// This is the histogram entry for a bucket, which contains a key, count, and optionally
    /// sub_aggregations.
    Histogram {
        /// The buckets.
        ///
        /// If there are holes depends on the request, if min_doc_count is 0, then there are no
        /// holes between the first and last bucket.
        /// See [`HistogramAggregation`](super::bucket::HistogramAggregation)
        buckets: BucketEntries<BucketEntry>,
    },
    /// This is the term result
    Terms {
        /// The buckets.
        ///
        /// See [`TermsAggregation`](super::bucket::TermsAggregation)
        buckets: Vec<BucketEntry>,
        /// The number of documents that didn’t make it into to TOP N due to shard_size or size
        sum_other_doc_count: u64,
        #[serde(skip_serializing_if = "Option::is_none")]
        /// The upper bound error for the doc count of each term.
        doc_count_error_upper_bound: Option<u64>,
    },
}

impl BucketResult {
    pub(crate) fn empty_from_req(req: &BucketAggregationInternal) -> crate::Result<Self> {
        let empty_bucket = IntermediateBucketResult::empty_from_req(&req.bucket_agg);
        empty_bucket.into_final_bucket_result(req)
    }
}

/// This is the wrapper of buckets entries, which can be vector or hashmap
/// depending on if it's keyed or not.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(untagged)]
pub enum BucketEntries<T> {
    /// Vector format bucket entries
    Vec(Vec<T>),
    /// HashMap format bucket entries
    HashMap(FnvHashMap<String, T>),
}

/// This is the default entry for a bucket, which contains a key, count, and optionally
/// sub_aggregations.
///
/// # JSON Format
/// ```json
/// {
///   ...
///     "my_histogram": {
///       "buckets": [
///         {
///           "key": "2.0",
///           "doc_count": 5
///         },
///         {
///           "key": "4.0",
///           "doc_count": 2
///         },
///         {
///           "key": "6.0",
///           "doc_count": 3
///         }
///       ]
///    }
///    ...
/// }
/// ```
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct BucketEntry {
    /// The identifier of the bucket.
    pub key: Key,
    /// Number of documents in the bucket.
    pub doc_count: u64,
    #[serde(flatten)]
    /// Sub-aggregations in this bucket.
    pub sub_aggregation: AggregationResults,
}
impl GetDocCount for &BucketEntry {
    fn doc_count(&self) -> u64 {
        self.doc_count
    }
}
impl GetDocCount for BucketEntry {
    fn doc_count(&self) -> u64 {
        self.doc_count
    }
}

/// This is the range entry for a bucket, which contains a key, count, and optionally
/// sub_aggregations.
///
/// # JSON Format
/// ```json
/// {
///   ...
///     "my_ranges": {
///       "buckets": [
///         {
///           "key": "*-10",
///           "to": 10,
///           "doc_count": 5
///         },
///         {
///           "key": "10-20",
///           "from": 10,
///           "to": 20,
///           "doc_count": 2
///         },
///         {
///           "key": "20-*",
///           "from": 20,
///           "doc_count": 3
///         }
///       ]
///    }
///    ...
/// }
/// ```
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct RangeBucketEntry {
    /// The identifier of the bucket.
    pub key: Key,
    /// Number of documents in the bucket.
    pub doc_count: u64,
    #[serde(flatten)]
    /// sub-aggregations in this bucket.
    pub sub_aggregation: AggregationResults,
    /// The from range of the bucket. Equals `f64::MIN` when `None`.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub from: Option<f64>,
    /// The to range of the bucket. Equals `f64::MAX` when `None`.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub to: Option<f64>,
}
