use crate::metric_primitive::MetricPrimitive;
use crate::timestamp::Timestamp;
use serde::Serialize;
use std::collections::BTreeMap;

/// Key type for the engine's primary index. Variant order matters: derived `Ord` compares the discriminant first, carving the map into contiguous ranges in declaration order (logs, params, metric declarations, buckets).
#[allow(dead_code)]
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Serialize)]
pub enum IndexKey {
    /// Marker for the start of the whole range. Never inserted, only navigated to.
    Start,
    IngestedLog {
        sequence: u64,
        timestamp: Timestamp,
    },
    /// Marker between the log range and the param range.
    LogParamSplit,
    ParamDeclaration {
        name: String,
    },
    /// Marker between the param range and the metric declaration range.
    ParamMetricSplit,
    MetricDeclaration {
        name: String,
    },
    /// Marker between metric declarations and their buckets.
    MetricBucketSplit,
    Bucket {
        metric_name: String,
        labels: BTreeMap<String, MetricPrimitive>,
    },
    /// Internal bookkeeping tracking the last event timestamp per metric+label, so a `Duration` param's first occurrence (which pushes no `Bucket`) still lets the next occurrence compute elapsed time.
    LastMetricEvent {
        metric_name: String,
        labels: BTreeMap<String, MetricPrimitive>,
    },
    /// Marker for the end of the whole range. Nothing sorts after this.
    End,
}