//! `swarm-metrics` — an agent's CLI for the swarm metrics store.
//!
//! The metrics-store sibling of `swarm-logs`: the same credential, the same
//! wrapper shape, and the store's own query language. Each verb is one GET
//! against the store's Prometheus-compatible read API through the
//! gateway, and prints the store's JSON answer unchanged for `jq`.
//!
//! **Read-only.** The verbs map onto `/api/v1/query`, `query_range`,
//! `series`, `labels` and `label/<name>/values`; nothing here writes.
//!
//! ⚠️ **The route applies no scoping.** Any authenticated caller reads the
//! whole swarm's metrics, every hive's.

mod auth;
mod query;

use anyhow::Result;
use clap::{Args, Parser, Subcommand};

use crate::query::{Request, Span};

#[derive(Parser)]
#[command(
    name = "swarm-metrics",
    version,
    about = "query the swarm's metrics store from an agent"
)]
struct Cli {
    #[command(subcommand)]
    command: Verb,
}

/// Window and cap for the discovery verbs.
#[derive(Args)]
struct SpanArgs {
    /// Start of the window: RFC 3339, a unix timestamp, or relative (`-1h`).
    ///
    /// Unset means the store's default: the last day, from 00:00 UTC.
    #[arg(long, allow_hyphen_values = true)]
    start: Option<String>,
    /// End of the window, in the same forms. Unset means now.
    #[arg(long, allow_hyphen_values = true)]
    end: Option<String>,
    /// Return at most this many entries.
    #[arg(long)]
    limit: Option<u64>,
}

impl From<SpanArgs> for Span {
    fn from(a: SpanArgs) -> Self {
        Self {
            start: a.start,
            end: a.end,
            limit: a.limit,
        }
    }
}

#[derive(Subcommand)]
enum Verb {
    /// Evaluate a `MetricsQL` (`PromQL`) expression at one instant.
    Query {
        /// The expression. Quote it: `{`, `|` and `"` are the shell's too.
        ///
        /// OTLP metric names keep their dots, so match them by
        /// `{__name__="jobq.nodes"}` rather than as a bare name.
        promql: String,
        /// The instant: RFC 3339, a unix timestamp, or relative (`-5m`).
        /// Unset means now.
        #[arg(long, allow_hyphen_values = true)]
        time: Option<String>,
    },

    /// Evaluate an expression over a window, one point per step.
    QueryRange {
        /// The expression, quoted as for `query`.
        promql: String,
        /// Start of the window: RFC 3339, a unix timestamp, or relative
        /// (`-1h`). Required, so a range is always bounded.
        #[arg(long, allow_hyphen_values = true)]
        start: String,
        /// End of the window, in the same forms. Unset means now.
        #[arg(long, allow_hyphen_values = true)]
        end: Option<String>,
        /// Seconds or a duration (`1m`) between points. Unset means the
        /// store's default.
        #[arg(long)]
        step: Option<String>,
    },

    /// List the series that match one or more selectors.
    Series {
        /// A series selector, such as `{"service.name"="nats"}`. Repeatable.
        #[arg(required = true)]
        matchers: Vec<String>,
        #[command(flatten)]
        span: SpanArgs,
    },

    /// List label names, optionally only those on matching series.
    Labels {
        /// A series selector to narrow to. Repeatable.
        #[arg(long = "match")]
        matchers: Vec<String>,
        #[command(flatten)]
        span: SpanArgs,
    },

    /// List one label's values; `__name__` lists every metric name.
    LabelValues {
        /// The label name.
        name: String,
        /// A series selector to narrow to. Repeatable.
        #[arg(long = "match")]
        matchers: Vec<String>,
        #[command(flatten)]
        span: SpanArgs,
    },

    /// Print this CLI's reference as markdown (source of `docs/tools/swarm-metrics-cli.md`).
    #[command(hide = true)]
    MarkdownDocs,
}

impl Verb {
    /// The store request this verb makes; `None` for the local-only verb.
    fn request(self) -> Option<Request> {
        Some(match self {
            Self::Query { promql, time } => Request::Query { promql, time },
            Self::QueryRange {
                promql,
                start,
                end,
                step,
            } => Request::QueryRange {
                promql,
                start,
                end,
                step,
            },
            Self::Series { matchers, span } => Request::Series {
                matchers,
                span: span.into(),
            },
            Self::Labels { matchers, span } => Request::Labels {
                matchers,
                span: span.into(),
            },
            Self::LabelValues {
                name,
                matchers,
                span,
            } => Request::LabelValues {
                name,
                matchers,
                span: span.into(),
            },
            Self::MarkdownDocs => return None,
        })
    }
}

fn main() -> Result<()> {
    let Some(request) = Cli::parse().command.request() else {
        // `show_footer(false)`: same as swarm-logs, the footer is not our prose.
        let options = clap_markdown::MarkdownOptions::new().show_footer(false);
        print!("{}", clap_markdown::help_markdown_custom::<Cli>(&options));
        return Ok(());
    };
    // Config read only for a store verb: `markdown-docs` runs in a nix check,
    // where no credential exists.
    swarm_secret_client::install_crypto_provider();
    let cfg = auth::Config::from_env()?;
    let stdout = std::io::stdout();
    query::run(&cfg, &request, &mut stdout.lock())
}

#[cfg(test)]
mod tests {
    use super::*;
    use clap::CommandFactory as _;

    fn parse(args: &[&str]) -> Option<Request> {
        Cli::try_parse_from(std::iter::once("swarm-metrics").chain(args.iter().copied()))
            .expect("parses")
            .command
            .request()
    }

    #[test]
    fn the_command_tree_is_well_formed() {
        Cli::command().debug_assert();
    }

    #[test]
    fn a_range_query_without_a_start_is_refused() {
        assert!(Cli::try_parse_from(["swarm-metrics", "query-range", "up"]).is_err());
    }

    #[test]
    fn series_needs_a_selector() {
        assert!(Cli::try_parse_from(["swarm-metrics", "series"]).is_err());
    }

    #[test]
    fn label_values_maps_name_matchers_and_span() {
        assert_eq!(
            parse(&[
                "label-values",
                "__name__",
                "--match",
                "{service.name=\"nats\"}",
                "--start",
                "-1d",
                "--limit",
                "5",
            ]),
            Some(Request::LabelValues {
                name: "__name__".into(),
                matchers: vec!["{service.name=\"nats\"}".into()],
                span: Span {
                    start: Some("-1d".into()),
                    end: None,
                    limit: Some(5),
                },
            })
        );
    }

    #[test]
    fn query_range_maps_its_window() {
        assert_eq!(
            parse(&["query-range", "up", "--start", "-1h", "--step", "1m"]),
            Some(Request::QueryRange {
                promql: "up".into(),
                start: "-1h".into(),
                end: None,
                step: Some("1m".into()),
            })
        );
    }

    #[test]
    fn markdown_docs_makes_no_request() {
        assert_eq!(parse(&["markdown-docs"]), None);
    }
}