//! The configuration reference on the documentation site describes every
//! field of the configuration's schema.
//!
//! The schema is `proto/config.proto`; the reference is
//! `docs/content/docs/reference/configuration.md`, with a section for each
//! message and enum (`## Peer`) that names each of its fields or values in
//! backquotes. A field added to the schema and not to the reference fails
//! here, so that operators can find every setting the daemon has.

use std::collections::BTreeMap;
use std::path::Path;

/// The messages and enums of a `.proto` file, each with its fields or
/// values, in the order they are declared.
fn declarations(proto: &str) -> BTreeMap<String, Vec<String>> {
    let mut found = BTreeMap::new();
    let mut current: Option<(String, Vec<String>)> = None;
    for line in proto.lines() {
        let line = line.trim();
        if line.starts_with("//") || line.is_empty() {
            continue;
        }
        let words: Vec<&str> = line.split_whitespace().collect();
        match words.as_slice() {
            ["message" | "enum", name, "{"] => current = Some((name.to_string(), Vec::new())),
            ["}"] => {
                if let Some((name, members)) = current.take() {
                    found.insert(name, members);
                }
            }
            // `repeated Peer peers = 4;`, `string name = 1;`, `PEER = 3;`
            _ => {
                let Some((_, members)) = current.as_mut() else {
                    continue;
                };
                let Some(at) = words.iter().position(|word| *word == "=") else {
                    continue;
                };
                let name = words[at - 1];
                // An enum's zero value is what is left out; there is
                // nothing to configure.
                if !name.ends_with("_UNSPECIFIED") {
                    members.push(name.to_string());
                }
            }
        }
    }
    found
}

/// The text of each `## ` section of a Markdown page, by its heading.
fn sections(page: &str) -> BTreeMap<String, String> {
    let mut found = BTreeMap::new();
    let mut current: Option<(String, String)> = None;
    for line in page.lines() {
        if let Some(heading) = line.strip_prefix("## ") {
            if let Some((name, text)) = current.take() {
                found.insert(name, text);
            }
            current = Some((heading.trim().to_string(), String::new()));
        } else if let Some((_, text)) = current.as_mut() {
            text.push_str(line);
            text.push('\n');
        }
    }
    if let Some((name, text)) = current {
        found.insert(name, text);
    }
    found
}

#[test]
fn the_configuration_reference_has_every_field() {
    let crate_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
    let proto = std::fs::read_to_string(crate_dir.join("proto/config.proto")).unwrap();
    let reference_path = crate_dir.join("../../docs/content/docs/reference/configuration.md");
    let reference = std::fs::read_to_string(&reference_path).unwrap();

    let declared = declarations(&proto);
    assert!(declared.contains_key("BgpConfig") && declared.contains_key("Peer"));
    let documented = sections(&reference);

    let mut missing = Vec::new();
    for (name, members) in &declared {
        let Some(section) = documented.get(name) else {
            missing.push(format!("a section `## {name}`"));
            continue;
        };
        for member in members {
            if !section.contains(&format!("`{member}`")) {
                missing.push(format!("`{member}` under `## {name}`"));
            }
        }
    }
    assert!(
        missing.is_empty(),
        "{} does not describe:\n  {}",
        reference_path.display(),
        missing.join("\n  ")
    );
}