use crate::data_value::{DataValue, MetricPrimitiveKind, RegexToMetricPrimitiveMatcher};
use crate::dto::{
    BucketValueDto, LogEntryDto, LogsParams, MetricDeclarationDto, ParamDeclarationDto,
    PromqlSeriesDto, StatsDto, TimelineBucketDto, TimelineParams,
};
use crate::index_key::IndexKey;
use crate::metric_primitive::{MetricPrimitive, Number};
use crate::promql::{self, AggOp, LabelMatcher, PromqlQuery};
use crate::timestamp::Timestamp;
use regex::Regex;
use serde::Deserialize;
use std::collections::BTreeMap;
use tokio::sync::{mpsc, oneshot};

pub struct IngestedLine {
    pub sequence: u64,
    pub timestamp: Timestamp,
    pub text: String,
}

/// Also the request body for `POST /api/params` (ticket 004): `Deserialize` is
/// derived directly on this engine type rather than adding a separate DTO,
/// since its shape is already exactly what the API needs.
#[derive(Debug, Clone, Deserialize)]
pub struct DeclareParamRequest {
    pub name: String,
    pub message_match_regex: String,
    pub capture_group: String,
    pub kind: MetricPrimitiveKind,
}

/// v1 mechanism: a metric declaration's params are derived purely from inline named
/// capture groups on the metric's own `message_match_regex` (each
/// `RegexToMetricPrimitiveMatcher::capture_group` must name a capture group on that
/// regex). Referencing an already-declared `ParamDeclaration` (001) by name is not
/// supported yet — that's left for a future ticket.
///
/// Also the request body for `POST /api/metrics` (ticket 004) — see
/// `DeclareParamRequest`'s doc comment for why `Deserialize` lives here rather
/// than on a separate DTO.
#[derive(Debug, Clone, Deserialize)]
pub struct DeclareMetricRequest {
    pub name: String,
    pub message_match_regex: String,
    pub params: Vec<RegexToMetricPrimitiveMatcher>,
}

#[allow(dead_code)]
pub enum EngineQuery {
    Logs(LogsParams),
    Timeline(TimelineParams),
    Stats,
    ParamDeclarations,
    MetricDeclarations,
    /// Bucket values for one metric (ticket 004's `GET /api/metrics/:name`).
    /// `labels_filter`, when present, keeps only buckets where every listed
    /// label matches — compared against each label value's `Display` form
    /// (see `MetricPrimitive`) rather than a typed value, since the filter
    /// arrives as plain strings off the query string.
    BucketValues {
        metric_name: String,
        labels_filter: Option<BTreeMap<String, String>>,
        start_ms: Option<i64>,
        end_ms: Option<i64>,
        since_sequence: Option<u64>,
        limit: Option<usize>,
    },
    /// PromQL query (ticket 013's `GET /api/query`). `query` is parsed here (rather
    /// than by the API handler) so parsing and evaluation both happen inside the
    /// single-owner engine loop, matching every other `EngineQuery` variant's
    /// pattern of evaluating in place against `index` with no copying. A malformed
    /// query is therefore only discovered once this reaches `handle_query`, hence
    /// `EngineResponse::Promql` carrying a `Result` rather than a bare `Vec`.
    Promql { query: String, start_ms: Option<i64>, end_ms: Option<i64> },
}

#[allow(dead_code)]
pub enum EngineMessage {
    Ingest(IngestedLine),
    DeclareParam {
        request: DeclareParamRequest,
        respond_to: oneshot::Sender<Result<(), String>>,
    },
    RemoveParamDeclaration {
        name: String,
        respond_to: oneshot::Sender<bool>,
    },
    DeclareMetric {
        request: DeclareMetricRequest,
        respond_to: oneshot::Sender<Result<(), String>>,
    },
    RemoveMetricDeclaration {
        name: String,
        respond_to: oneshot::Sender<bool>,
    },
    Query {
        query: EngineQuery,
        respond_to: oneshot::Sender<EngineResponse>,
    },
}

#[allow(dead_code)]
pub enum EngineResponse {
    Logs(Vec<LogEntryDto>),
    Timeline(Vec<TimelineBucketDto>),
    Stats(StatsDto),
    ParamDeclarations(Vec<ParamDeclarationDto>),
    MetricDeclarations(Vec<MetricDeclarationDto>),
    BucketValues(Vec<BucketValueDto>),
    /// `Err` holds a human-readable message for a malformed query (see
    /// `crate::promql::parse_query`), which the API layer maps to a 400 response.
    Promql(Result<Vec<PromqlSeriesDto>, String>),
}

pub type EngineHandle = mpsc::Sender<EngineMessage>;

/// Sole owner of the primary index. Runs single-threaded so the map never needs a
/// lock, and does its own response serialization/DTO construction so callers never
/// have to clone the index to answer a query.
pub async fn run(mut rx: mpsc::Receiver<EngineMessage>) {
    let mut index: BTreeMap<IndexKey, DataValue> = BTreeMap::new();

    while let Some(message) = rx.recv().await {
        match message {
            EngineMessage::Ingest(line) => {
                let IngestedLine { sequence, timestamp, text } = line;
                index.insert(
                    IndexKey::IngestedLog { sequence, timestamp },
                    DataValue::LogLiteral { text: text.clone() },
                );
                apply_all_metrics(&mut index, sequence, timestamp, &text);
            }
            EngineMessage::DeclareParam { request, respond_to } => {
                let result = declare_param(&mut index, request);
                let _ = respond_to.send(result);
            }
            EngineMessage::RemoveParamDeclaration { name, respond_to } => {
                let existed = index.remove(&IndexKey::ParamDeclaration { name }).is_some();
                let _ = respond_to.send(existed);
            }
            EngineMessage::DeclareMetric { request, respond_to } => {
                let result = declare_metric(&mut index, request);
                let _ = respond_to.send(result);
            }
            EngineMessage::RemoveMetricDeclaration { name, respond_to } => {
                let existed = index.remove(&IndexKey::MetricDeclaration { name }).is_some();
                let _ = respond_to.send(existed);
            }
            EngineMessage::Query { query, respond_to } => {
                let response = handle_query(&index, query);
                let _ = respond_to.send(response);
            }
        }
    }
}

/// Validates the regex and capture group before storing, so a bad declaration is
/// rejected up front rather than silently stored (or discovered later at derivation
/// time).
fn declare_param(
    index: &mut BTreeMap<IndexKey, DataValue>,
    request: DeclareParamRequest,
) -> Result<(), String> {
    let re = Regex::new(&request.message_match_regex)
        .map_err(|err| format!("invalid regex: {err}"))?;
    if !re.capture_names().flatten().any(|name| name == request.capture_group) {
        return Err(format!(
            "regex has no capture group named '{}'",
            request.capture_group
        ));
    }

    index.insert(
        IndexKey::ParamDeclaration { name: request.name },
        DataValue::ParamDeclaration {
            message_match_regex: request.message_match_regex,
            capture_group: request.capture_group,
            kind: request.kind,
        },
    );
    Ok(())
}

/// Validates the regex and every param matcher's capture-group reference before
/// storing. All matchers are checked (not just the first bad one) so a rejection can
/// report every problem at once.
fn declare_metric(
    index: &mut BTreeMap<IndexKey, DataValue>,
    request: DeclareMetricRequest,
) -> Result<(), String> {
    let re = Regex::new(&request.message_match_regex)
        .map_err(|err| format!("invalid regex: {err}"))?;

    let errors: Vec<String> = request
        .params
        .iter()
        .filter(|matcher| {
            !re.capture_names().flatten().any(|name| name == matcher.capture_group)
        })
        .map(|matcher| {
            format!(
                "param '{}' references capture group '{}', which the regex does not have",
                matcher.param_name, matcher.capture_group
            )
        })
        .collect();
    if !errors.is_empty() {
        return Err(errors.join("; "));
    }

    backfill_metric(index, &request.name, &re, &request.params);
    index.insert(
        IndexKey::MetricDeclaration { name: request.name },
        DataValue::MetricDeclaration {
            message_match_regex: request.message_match_regex,
            params: request.params,
        },
    );
    Ok(())
}

/// Parses a single captured substring into the `MetricPrimitive` its param declares.
/// Returns `None` on a parse failure (e.g. a `Number` param whose capture isn't
/// numeric), which the caller treats as "this match doesn't apply".
fn parse_metric_primitive(raw: &str, kind: MetricPrimitiveKind) -> Option<MetricPrimitive> {
    match kind {
        MetricPrimitiveKind::String => Some(MetricPrimitive::String(raw.to_string())),
        MetricPrimitiveKind::Number => raw
            .parse::<i64>()
            .map(Number::Int)
            .or_else(|_| raw.parse::<f64>().map(Number::Float))
            .ok()
            .map(MetricPrimitive::Number),
        MetricPrimitiveKind::Timestamp => {
            crate::filter_datetime::parse_datetime(raw, Timestamp::now())
                .ok()
                .map(MetricPrimitive::Timestamp)
        }
    }
}

/// Runs one metric's regex against a single log line and, on a match, appends a
/// bucket value entry.
///
/// Design decision: `Bucket.labels` is the only structured place a `Bucket` key has
/// for a metric's declared params, so v1 folds ALL of a metric's params into
/// `labels` rather than splitting them into "label" vs "value" params. The stored
/// value is therefore a fixed presence marker (`MetricPrimitive::Number(Number::Int(1))`)
/// — a bucket's `values` is the timeseries of *when that label combination occurred*
/// (a count/occurrence series), not a record of the captured values themselves. If a
/// param's capture group doesn't match, or its captured text fails to parse as its
/// declared `kind`, the whole match is skipped for this line rather than storing a
/// partially-labeled bucket.
fn apply_metric_to_log(
    index: &mut BTreeMap<IndexKey, DataValue>,
    metric_name: &str,
    regex: &Regex,
    params: &[RegexToMetricPrimitiveMatcher],
    sequence: u64,
    timestamp: Timestamp,
    text: &str,
) {
    let Some(captures) = regex.captures(text) else {
        return;
    };

    let mut labels = BTreeMap::new();
    for matcher in params {
        let Some(raw) = captures.name(&matcher.capture_group) else {
            return;
        };
        let Some(value) = parse_metric_primitive(raw.as_str(), matcher.kind) else {
            return;
        };
        labels.insert(matcher.param_name.clone(), value);
    }

    let key = IndexKey::Bucket { metric_name: metric_name.to_string(), labels };
    let entry = index
        .entry(key)
        .or_insert_with(|| DataValue::BucketValue { values: Vec::new() });
    if let DataValue::BucketValue { values } = entry {
        values.push((sequence, timestamp, MetricPrimitive::Number(Number::Int(1))));
    }
}

/// Applies a newly-declared metric to every already-ingested log, so a metric
/// declared after logs have already arrived still gets populated buckets for them
/// (backfill), rather than only reflecting logs ingested from that point on.
fn backfill_metric(
    index: &mut BTreeMap<IndexKey, DataValue>,
    metric_name: &str,
    regex: &Regex,
    params: &[RegexToMetricPrimitiveMatcher],
) {
    let lines: Vec<(u64, Timestamp, String)> = logs_range(index)
        .map(|(sequence, timestamp, text)| (sequence, timestamp, text.to_string()))
        .collect();
    for (sequence, timestamp, text) in lines {
        apply_metric_to_log(index, metric_name, regex, params, sequence, timestamp, &text);
    }
}

/// Runs every currently-declared metric's regex against one newly-ingested log line,
/// updating whichever buckets match. A line matching zero metrics leaves the bucket
/// range untouched.
fn apply_all_metrics(
    index: &mut BTreeMap<IndexKey, DataValue>,
    sequence: u64,
    timestamp: Timestamp,
    text: &str,
) {
    let metrics: Vec<(String, String, Vec<RegexToMetricPrimitiveMatcher>)> =
        metric_declarations_range(index)
            .map(|(name, message_match_regex, params)| {
                (name.to_string(), message_match_regex.to_string(), params.to_vec())
            })
            .collect();
    for (name, message_match_regex, params) in metrics {
        if let Ok(re) = Regex::new(&message_match_regex) {
            apply_metric_to_log(index, &name, &re, &params, sequence, timestamp, text);
        }
    }
}

/// Bucket values for one metric, in insertion order, optionally filtered to a single
/// exact label combination. Used directly by tests (exact-match filtering) and, via
/// `EngineQuery::BucketValues` in `handle_query` below, by the metrics API (ticket
/// 004) — which layers its own textual label-filter and time/sequence-range
/// filtering on top rather than using this function's `labels_filter` parameter.
fn bucket_values<'a>(
    index: &'a BTreeMap<IndexKey, DataValue>,
    metric_name: &'a str,
    labels_filter: Option<&'a BTreeMap<String, MetricPrimitive>>,
) -> impl Iterator<Item = (&'a BTreeMap<String, MetricPrimitive>, &'a (u64, Timestamp, MetricPrimitive))> + 'a
{
    index
        .range(IndexKey::MetricBucketSplit..IndexKey::End)
        .filter_map(move |(key, value)| match (key, value) {
            (IndexKey::Bucket { metric_name: name, labels }, DataValue::BucketValue { values })
                if name == metric_name && labels_filter.is_none_or(|filter| filter == labels) =>
            {
                Some(values.iter().map(move |entry| (labels, entry)))
            }
            _ => None,
        })
        .flatten()
}

fn metric_declarations_range(
    index: &BTreeMap<IndexKey, DataValue>,
) -> impl Iterator<Item = (&str, &str, &[RegexToMetricPrimitiveMatcher])> {
    index
        .range(IndexKey::ParamMetricSplit..IndexKey::MetricBucketSplit)
        .filter_map(|(key, value)| match (key, value) {
            (
                IndexKey::MetricDeclaration { name },
                DataValue::MetricDeclaration { message_match_regex, params },
            ) => Some((name.as_str(), message_match_regex.as_str(), params.as_slice())),
            _ => None,
        })
}

fn param_declarations_range(
    index: &BTreeMap<IndexKey, DataValue>,
) -> impl Iterator<Item = (&str, &str, &str, MetricPrimitiveKind)> {
    index
        .range(IndexKey::LogParamSplit..IndexKey::ParamMetricSplit)
        .filter_map(|(key, value)| match (key, value) {
            (
                IndexKey::ParamDeclaration { name },
                DataValue::ParamDeclaration { message_match_regex, capture_group, kind },
            ) => Some((name.as_str(), message_match_regex.as_str(), capture_group.as_str(), *kind)),
            _ => None,
        })
}

fn logs_range(index: &BTreeMap<IndexKey, DataValue>) -> impl Iterator<Item = (u64, Timestamp, &str)> {
    index.range(IndexKey::Start..IndexKey::LogParamSplit).filter_map(|(key, value)| {
        match (key, value) {
            (IndexKey::IngestedLog { sequence, timestamp }, DataValue::LogLiteral { text }) => {
                Some((*sequence, *timestamp, text.as_str()))
            }
            _ => None,
        }
    })
}

fn handle_query(index: &BTreeMap<IndexKey, DataValue>, query: EngineQuery) -> EngineResponse {
    match query {
        EngineQuery::Logs(params) => {
            let limit = params.limit.unwrap_or(500).min(10_000);
            let entries: Vec<LogEntryDto> = logs_range(index)
                .filter(|(sequence, timestamp, _)| {
                    params.since_sequence.is_none_or(|since| *sequence > since)
                        && params.start_ms.is_none_or(|start| timestamp.as_millis() >= start)
                        && params.end_ms.is_none_or(|end| timestamp.as_millis() <= end)
                })
                .take(limit)
                .map(|(sequence, timestamp, text)| LogEntryDto {
                    sequence,
                    timestamp_ms: timestamp.as_millis(),
                    text: text.to_string(),
                })
                .collect();
            EngineResponse::Logs(entries)
        }
        EngineQuery::Timeline(params) => {
            let bucket_ms = params.bucket_ms.unwrap_or(1_000).max(1);
            let mut buckets: BTreeMap<i64, u64> = BTreeMap::new();
            for (_, timestamp, _) in logs_range(index).filter(|(_, timestamp, _)| {
                params.start_ms.is_none_or(|start| timestamp.as_millis() >= start)
                    && params.end_ms.is_none_or(|end| timestamp.as_millis() <= end)
            }) {
                let bucket_start = (timestamp.as_millis() / bucket_ms) * bucket_ms;
                *buckets.entry(bucket_start).or_insert(0) += 1;
            }
            let out = buckets
                .into_iter()
                .map(|(start_ms, count)| TimelineBucketDto { start_ms, count })
                .collect();
            EngineResponse::Timeline(out)
        }
        EngineQuery::Stats => {
            let mut log_count = 0u64;
            let mut first_sequence = None;
            let mut last_sequence = None;
            let mut first_timestamp_ms = None;
            let mut last_timestamp_ms = None;
            for (sequence, timestamp, _) in logs_range(index) {
                log_count += 1;
                first_sequence.get_or_insert(sequence);
                last_sequence = Some(sequence);
                first_timestamp_ms.get_or_insert(timestamp.as_millis());
                last_timestamp_ms = Some(timestamp.as_millis());
            }
            EngineResponse::Stats(StatsDto {
                log_count,
                first_sequence,
                last_sequence,
                first_timestamp_ms,
                last_timestamp_ms,
            })
        }
        EngineQuery::ParamDeclarations => {
            let declarations = param_declarations_range(index)
                .map(|(name, message_match_regex, capture_group, kind)| ParamDeclarationDto {
                    name: name.to_string(),
                    message_match_regex: message_match_regex.to_string(),
                    capture_group: capture_group.to_string(),
                    kind,
                })
                .collect();
            EngineResponse::ParamDeclarations(declarations)
        }
        EngineQuery::MetricDeclarations => {
            let declarations = metric_declarations_range(index)
                .map(|(name, message_match_regex, params)| MetricDeclarationDto {
                    name: name.to_string(),
                    message_match_regex: message_match_regex.to_string(),
                    params: params.to_vec(),
                })
                .collect();
            EngineResponse::MetricDeclarations(declarations)
        }
        EngineQuery::BucketValues {
            metric_name,
            labels_filter,
            start_ms,
            end_ms,
            since_sequence,
            limit,
        } => {
            let limit = limit.unwrap_or(500).min(10_000);
            let values: Vec<BucketValueDto> = bucket_values(index, &metric_name, None)
                .filter(|(labels, _)| {
                    labels_filter.as_ref().is_none_or(|filter| {
                        filter.iter().all(|(name, expected)| {
                            labels
                                .get(name)
                                .is_some_and(|value| &value.to_string() == expected)
                        })
                    })
                })
                .filter(|(_, (sequence, timestamp, _))| {
                    since_sequence.is_none_or(|since| *sequence > since)
                        && start_ms.is_none_or(|start| timestamp.as_millis() >= start)
                        && end_ms.is_none_or(|end| timestamp.as_millis() <= end)
                })
                .take(limit)
                .map(|(labels, (sequence, timestamp, value))| BucketValueDto {
                    labels: labels.clone(),
                    sequence: *sequence,
                    timestamp_ms: timestamp.as_millis(),
                    value: value.clone(),
                })
                .collect();
            EngineResponse::BucketValues(values)
        }
        EngineQuery::Promql { query, start_ms, end_ms } => {
            let response = promql::parse_query(&query)
                .map(|parsed| evaluate_promql(index, &parsed, start_ms, end_ms));
            EngineResponse::Promql(response)
        }
    }
}

/// Coerces a bucket's stored `MetricPrimitive` into a plottable `f64` for
/// `PromqlSeriesDto`:
/// - `Number` uses its underlying numeric value.
/// - `Timestamp` uses its millisecond value (arbitrary but at least meaningful/
///   orderable, since there's no other sensible single number for a point in time).
/// - `String` has no numeric reading at all, so it falls back to `1.0` — i.e. it is
///   treated the same as the presence/occurrence marker `apply_metric_to_log` already
///   stores for every bucket value today (ticket 003), meaning a PromQL series over a
///   `String`-valued bucket becomes an occurrence-count series rather than being
///   skipped. This keeps every declared metric queryable (matching the ticket's
///   "documented fallback" requirement) rather than silently omitting non-numeric
///   series.
fn coerce_to_f64(value: &MetricPrimitive) -> f64 {
    match value {
        MetricPrimitive::Number(n) => match n {
            Number::Int(v) => *v as f64,
            Number::Float(v) => *v,
        },
        MetricPrimitive::Timestamp(ts) => ts.as_millis() as f64,
        MetricPrimitive::String(_) => 1.0,
    }
}

/// True when every matcher in `matchers` is satisfied by `labels` (compared against
/// each label value's `Display` form, same convention as `EngineQuery::BucketValues`'s
/// `labels_filter`). Unmatched/extra labels on the bucket are ignored — a matcher list
/// only needs to be a subset.
fn matches_label_matchers(
    labels: &BTreeMap<String, MetricPrimitive>,
    matchers: &[LabelMatcher],
) -> bool {
    matchers.iter().all(|matcher| {
        labels.get(&matcher.name).is_some_and(|value| value.to_string() == matcher.value)
    })
}

/// Evaluates a parsed PromQL query against `index`, producing chart-ready series.
///
/// Baseline (no aggregation wrapper): one output series per distinct label
/// combination that matches `parsed.metric_name` + `parsed.matchers`, with that
/// combination's bucket values as `(timestamp_ms, value)` points (see
/// `coerce_to_f64`), sorted by timestamp.
///
/// `sum()`/`avg()`: merges every matching series' points by exact millisecond
/// timestamp (summing, or averaging, the values that land on the same timestamp
/// across series) into a single output series with empty labels — the aggregation
/// collapses the label dimension, same as PromQL's `sum by ()`/`avg by ()` default.
///
/// `rate()`: requires (and, per `promql::parse_query`, is only ever given) a range
/// selector. This is a simplified, single-point-per-series rate rather than PromQL's
/// true sliding-window-per-evaluation-step semantics: for each matching series, it
/// takes the window `(last_point_ts - range, last_point_ts]` and divides the number
/// of points falling in that window by the range's duration in seconds, producing one
/// `(last_point_ts, rate)` point per series. Since bucket values are occurrence
/// markers rather than cumulative counters (ticket 003), an occurrence-count-per-
/// second reading is the meaningful analogue of PromQL's counter-increase rate here.
fn evaluate_promql(
    index: &BTreeMap<IndexKey, DataValue>,
    parsed: &PromqlQuery,
    start_ms: Option<i64>,
    end_ms: Option<i64>,
) -> Vec<PromqlSeriesDto> {
    let mut series_points: BTreeMap<BTreeMap<String, String>, Vec<(i64, f64)>> = BTreeMap::new();
    for (labels, (_, timestamp, value)) in bucket_values(index, &parsed.metric_name, None)
        .filter(|(labels, _)| matches_label_matchers(labels, &parsed.matchers))
        .filter(|(_, (_, timestamp, _))| {
            start_ms.is_none_or(|start| timestamp.as_millis() >= start)
                && end_ms.is_none_or(|end| timestamp.as_millis() <= end)
        })
    {
        let display_labels: BTreeMap<String, String> =
            labels.iter().map(|(name, value)| (name.clone(), value.to_string())).collect();
        series_points
            .entry(display_labels)
            .or_default()
            .push((timestamp.as_millis(), coerce_to_f64(value)));
    }
    for points in series_points.values_mut() {
        points.sort_by_key(|(timestamp_ms, _)| *timestamp_ms);
    }

    match parsed.agg {
        None => series_points
            .into_iter()
            .map(|(labels, points)| PromqlSeriesDto { labels, points })
            .collect(),
        Some(AggOp::Sum) | Some(AggOp::Avg) => {
            let mut grouped: BTreeMap<i64, Vec<f64>> = BTreeMap::new();
            for points in series_points.values() {
                for (timestamp_ms, value) in points {
                    grouped.entry(*timestamp_ms).or_default().push(*value);
                }
            }
            let is_avg = parsed.agg == Some(AggOp::Avg);
            let points = grouped
                .into_iter()
                .map(|(timestamp_ms, values)| {
                    let sum: f64 = values.iter().sum();
                    let value = if is_avg { sum / values.len() as f64 } else { sum };
                    (timestamp_ms, value)
                })
                .collect();
            vec![PromqlSeriesDto { labels: BTreeMap::new(), points }]
        }
        Some(AggOp::Rate) => {
            // Validated by `promql::parse_query`: `rate()` never parses without one.
            let range_ms = parsed.range.expect("rate() always carries a range").as_millis() as i64;
            let range_seconds = range_ms as f64 / 1000.0;
            series_points
                .into_iter()
                .filter_map(|(labels, points)| {
                    let last_ts = points.last()?.0;
                    let window_start = last_ts - range_ms;
                    let count_in_window =
                        points.iter().filter(|(ts, _)| *ts > window_start && *ts <= last_ts).count();
                    let rate = count_in_window as f64 / range_seconds;
                    Some(PromqlSeriesDto { labels, points: vec![(last_ts, rate)] })
                })
                .collect()
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn request(name: &str, pattern: &str, capture_group: &str) -> DeclareParamRequest {
        DeclareParamRequest {
            name: name.to_string(),
            message_match_regex: pattern.to_string(),
            capture_group: capture_group.to_string(),
            kind: MetricPrimitiveKind::String,
        }
    }

    #[test]
    fn declares_valid_param() {
        let mut index = BTreeMap::new();
        let result = declare_param(&mut index, request("level", r"level=(?P<level>\w+)", "level"));
        assert!(result.is_ok());

        let declarations: Vec<_> = param_declarations_range(&index).collect();
        assert_eq!(declarations.len(), 1);
        assert_eq!(declarations[0].0, "level");
        assert_eq!(declarations[0].1, r"level=(?P<level>\w+)");
        assert_eq!(declarations[0].2, "level");
    }

    #[test]
    fn rejects_invalid_regex() {
        let mut index = BTreeMap::new();
        let result = declare_param(&mut index, request("level", "level=(", "level"));
        assert!(result.is_err());
        assert!(index.is_empty());
    }

    #[test]
    fn rejects_unknown_capture_group() {
        let mut index = BTreeMap::new();
        let result = declare_param(
            &mut index,
            request("level", r"level=(?P<level>\w+)", "missing"),
        );
        assert!(result.is_err());
        assert!(index.is_empty());
    }

    #[test]
    fn declarations_stay_within_their_range() {
        let mut index = BTreeMap::new();
        index.insert(
            IndexKey::IngestedLog { sequence: 0, timestamp: Timestamp::from_millis(0) },
            DataValue::LogLiteral { text: "hello".to_string() },
        );
        declare_param(&mut index, request("level", r"level=(?P<level>\w+)", "level")).unwrap();
        index.insert(
            IndexKey::MetricDeclaration { name: "requests".to_string() },
            DataValue::MetricDeclaration {
                message_match_regex: "x".to_string(),
                params: vec![],
            },
        );

        let declarations: Vec<_> = param_declarations_range(&index).collect();
        assert_eq!(declarations.len(), 1);
        assert_eq!(declarations[0].0, "level");

        for key in index.range(IndexKey::LogParamSplit..IndexKey::ParamMetricSplit).map(|(k, _)| k) {
            assert!(matches!(key, IndexKey::ParamDeclaration { .. }));
        }
    }

    #[test]
    fn removes_declaration() {
        let mut index = BTreeMap::new();
        declare_param(&mut index, request("level", r"level=(?P<level>\w+)", "level")).unwrap();
        assert!(index.remove(&IndexKey::ParamDeclaration { name: "level".to_string() }).is_some());
        assert!(param_declarations_range(&index).next().is_none());
    }

    fn metric_request(
        name: &str,
        pattern: &str,
        params: Vec<(&str, &str, MetricPrimitiveKind)>,
    ) -> DeclareMetricRequest {
        DeclareMetricRequest {
            name: name.to_string(),
            message_match_regex: pattern.to_string(),
            params: params
                .into_iter()
                .map(|(param_name, capture_group, kind)| RegexToMetricPrimitiveMatcher {
                    param_name: param_name.to_string(),
                    capture_group: capture_group.to_string(),
                    kind,
                })
                .collect(),
        }
    }

    #[test]
    fn declares_valid_metric() {
        let mut index = BTreeMap::new();
        let result = declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+) duration=(?P<duration>\d+)",
                vec![
                    ("path", "path", MetricPrimitiveKind::String),
                    ("duration", "duration", MetricPrimitiveKind::Number),
                ],
            ),
        );
        assert!(result.is_ok());

        let declarations: Vec<_> = metric_declarations_range(&index).collect();
        assert_eq!(declarations.len(), 1);
        assert_eq!(declarations[0].0, "requests");
        assert_eq!(
            declarations[0].1,
            r"request path=(?P<path>\S+) duration=(?P<duration>\d+)"
        );
        assert_eq!(declarations[0].2.len(), 2);
    }

    #[test]
    fn rejects_invalid_metric_regex() {
        let mut index = BTreeMap::new();
        let result = declare_metric(&mut index, metric_request("requests", "path=(", vec![]));
        assert!(result.is_err());
        assert!(index.is_empty());
    }

    #[test]
    fn rejects_metric_matcher_with_unknown_capture_group() {
        let mut index = BTreeMap::new();
        let result = declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![
                    ("path", "path", MetricPrimitiveKind::String),
                    ("duration", "duration", MetricPrimitiveKind::Number),
                ],
            ),
        );
        assert!(result.is_err());
        // Both matchers are validated: the error mentions the one that's actually bad.
        assert!(result.unwrap_err().contains("duration"));
        assert!(index.is_empty());
    }

    #[test]
    fn metric_declarations_stay_within_their_range() {
        let mut index = BTreeMap::new();
        index.insert(
            IndexKey::IngestedLog { sequence: 0, timestamp: Timestamp::from_millis(0) },
            DataValue::LogLiteral { text: "hello".to_string() },
        );
        declare_param(&mut index, request("level", r"level=(?P<level>\w+)", "level")).unwrap();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"duration=(?P<duration>\d+)",
                vec![("duration", "duration", MetricPrimitiveKind::Number)],
            ),
        )
        .unwrap();

        let declarations: Vec<_> = metric_declarations_range(&index).collect();
        assert_eq!(declarations.len(), 1);
        assert_eq!(declarations[0].0, "requests");

        for key in index.range(IndexKey::ParamMetricSplit..IndexKey::MetricBucketSplit).map(|(k, _)| k) {
            assert!(matches!(key, IndexKey::MetricDeclaration { .. }));
        }
    }

    #[test]
    fn removes_metric_declaration() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"duration=(?P<duration>\d+)",
                vec![("duration", "duration", MetricPrimitiveKind::Number)],
            ),
        )
        .unwrap();
        assert!(index.remove(&IndexKey::MetricDeclaration { name: "requests".to_string() }).is_some());
        assert!(metric_declarations_range(&index).next().is_none());
    }

    fn ingest_log(index: &mut BTreeMap<IndexKey, DataValue>, sequence: u64, text: &str) {
        let timestamp = Timestamp::from_millis(sequence as i64);
        index.insert(
            IndexKey::IngestedLog { sequence, timestamp },
            DataValue::LogLiteral { text: text.to_string() },
        );
        apply_all_metrics(index, sequence, timestamp, text);
    }

    #[test]
    fn declaring_metric_backfills_matching_logs() {
        let mut index = BTreeMap::new();
        ingest_log(&mut index, 0, "request path=/a duration=1");
        ingest_log(&mut index, 1, "request path=/b duration=2");
        ingest_log(&mut index, 2, "unrelated line");

        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+) duration=(?P<duration>\d+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();

        let values: Vec<_> = bucket_values(&index, "requests", None).collect();
        assert_eq!(values.len(), 2);
    }

    #[test]
    fn ingesting_after_declaration_updates_buckets_live() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();

        ingest_log(&mut index, 0, "request path=/a");

        let values: Vec<_> = bucket_values(&index, "requests", None).collect();
        assert_eq!(values.len(), 1);
        assert_eq!(values[0].1.0, 0);
    }

    #[test]
    fn non_matching_log_leaves_bucket_range_untouched() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();

        ingest_log(&mut index, 0, "totally unrelated line");

        assert!(
            index
                .range(IndexKey::MetricBucketSplit..IndexKey::End)
                .find(|(key, _)| matches!(key, IndexKey::Bucket { .. }))
                .is_none()
        );
    }

    #[test]
    fn bucket_values_preserve_insertion_order() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();

        ingest_log(&mut index, 5, "request path=/a");
        ingest_log(&mut index, 2, "request path=/a");
        ingest_log(&mut index, 9, "request path=/a");

        let sequences: Vec<u64> = bucket_values(&index, "requests", None)
            .map(|(_, (sequence, _, _))| *sequence)
            .collect();
        assert_eq!(sequences, vec![5, 2, 9]);
    }

    #[test]
    fn differing_label_combinations_produce_distinct_buckets() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();

        ingest_log(&mut index, 0, "request path=/a");
        ingest_log(&mut index, 1, "request path=/b");

        let bucket_keys: Vec<_> = index
            .range(IndexKey::MetricBucketSplit..IndexKey::End)
            .filter(|(key, _)| matches!(key, IndexKey::Bucket { .. }))
            .collect();
        assert_eq!(bucket_keys.len(), 2);
        for (_, value) in &bucket_keys {
            match value {
                DataValue::BucketValue { values } => assert_eq!(values.len(), 1),
                _ => panic!("expected BucketValue"),
            }
        }
    }

    #[test]
    fn single_log_line_can_match_multiple_metrics() {
        let mut index = BTreeMap::new();
        declare_metric(
            &mut index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+) duration=(?P<duration>\d+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();
        declare_metric(
            &mut index,
            metric_request(
                "durations",
                r"request path=(?P<path>\S+) duration=(?P<duration>\d+)",
                vec![("duration", "duration", MetricPrimitiveKind::Number)],
            ),
        )
        .unwrap();

        ingest_log(&mut index, 0, "request path=/a duration=5");

        assert_eq!(bucket_values(&index, "requests", None).count(), 1);
        assert_eq!(bucket_values(&index, "durations", None).count(), 1);
    }

    fn declare_requests_metric(index: &mut BTreeMap<IndexKey, DataValue>) {
        declare_metric(
            index,
            metric_request(
                "requests",
                r"request path=(?P<path>\S+)",
                vec![("path", "path", MetricPrimitiveKind::String)],
            ),
        )
        .unwrap();
    }

    #[test]
    fn promql_query_selects_matching_label_combination() {
        let mut index = BTreeMap::new();
        declare_requests_metric(&mut index);
        ingest_log(&mut index, 0, "request path=/a");
        ingest_log(&mut index, 1, "request path=/b");
        ingest_log(&mut index, 2, "request path=/a");

        let parsed = promql::parse_query(r#"requests{path="/a"}"#).unwrap();
        let series = evaluate_promql(&index, &parsed, None, None);

        assert_eq!(series.len(), 1);
        assert_eq!(series[0].labels.get("path").map(String::as_str), Some("/a"));
        // Occurrence markers coerce to 1.0 (see `coerce_to_f64`); timestamps come from
        // `ingest_log`'s `sequence as millis` helper.
        assert_eq!(series[0].points, vec![(0, 1.0), (2, 1.0)]);
    }

    #[test]
    fn promql_query_with_no_matching_labels_returns_no_series() {
        let mut index = BTreeMap::new();
        declare_requests_metric(&mut index);
        ingest_log(&mut index, 0, "request path=/a");

        let parsed = promql::parse_query(r#"requests{path="/nope"}"#).unwrap();
        let series = evaluate_promql(&index, &parsed, None, None);
        assert!(series.is_empty());
    }

    #[test]
    fn promql_sum_aggregates_across_label_combinations() {
        let mut index = BTreeMap::new();
        declare_requests_metric(&mut index);
        ingest_log(&mut index, 0, "request path=/a");
        ingest_log(&mut index, 0, "request path=/b");

        let parsed = promql::parse_query("sum(requests)").unwrap();
        let series = evaluate_promql(&index, &parsed, None, None);

        assert_eq!(series.len(), 1);
        assert!(series[0].labels.is_empty());
        assert_eq!(series[0].points, vec![(0, 2.0)]);
    }

    #[test]
    fn promql_range_bounds_filter_points_via_start_end_ms() {
        let mut index = BTreeMap::new();
        declare_requests_metric(&mut index);
        ingest_log(&mut index, 0, "request path=/a");
        ingest_log(&mut index, 5, "request path=/a");
        ingest_log(&mut index, 10, "request path=/a");

        let parsed = promql::parse_query("requests").unwrap();
        let series = evaluate_promql(&index, &parsed, Some(1), Some(9));

        assert_eq!(series.len(), 1);
        assert_eq!(series[0].points, vec![(5, 1.0)]);
    }

    #[test]
    fn handle_query_promql_rejects_malformed_query() {
        let index = BTreeMap::new();
        let response = handle_query(
            &index,
            EngineQuery::Promql {
                query: "not a valid promql query(".to_string(),
                start_ms: None,
                end_ms: None,
            },
        );
        match response {
            EngineResponse::Promql(Err(message)) => assert!(!message.is_empty()),
            _ => panic!("expected EngineResponse::Promql(Err(_))"),
        }
    }

    #[test]
    fn handle_query_promql_returns_series_for_valid_query() {
        let mut index = BTreeMap::new();
        declare_requests_metric(&mut index);
        ingest_log(&mut index, 0, "request path=/a");

        let response = handle_query(
            &index,
            EngineQuery::Promql {
                query: r#"requests{path="/a"}"#.to_string(),
                start_ms: None,
                end_ms: None,
            },
        );
        match response {
            EngineResponse::Promql(Ok(series)) => {
                assert_eq!(series.len(), 1);
                assert_eq!(series[0].points, vec![(0, 1.0)]);
            }
            _ => panic!("expected EngineResponse::Promql(Ok(_))"),
        }
    }
}