// Copyright 2020 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use {
    anyhow::{bail, Error},
    glob::glob,
    lazy_static::lazy_static,
    regex::Regex,
    serde_derive::Deserialize,
    std::collections::HashMap,
};

/// The outer map is service_name; the inner is tag.
pub(crate) type Config = HashMap<String, HashMap<String, TaggedPersist>>;

/// Schema for config-file entries. Each config file is a JSON array of these.
#[derive(Deserialize, Default, Debug, PartialEq)]
#[serde(deny_unknown_fields)]
pub struct TaggedPersist {
    /// The Inspect data defined here will be published under this tag.
    /// Tags must not be duplicated within a service, even between files.
    /// Tags must conform to /[a-z][a-z-]*/.
    pub tag: String,
    /// Each tag will only be requestable via a named service. Multiple tags can use the
    /// same service name, which will be published and routed as DataPersistence_{service_name}.
    /// Service names must conform to /[a-z][a-z-]*/.
    pub service_name: String,
    /// These selectors will be fetched and stored for publication on the next boot.
    pub selectors: Vec<String>,
    /// This is the max size of the file saved, which is the JSON-serialized version
    /// of the selectors' data.
    pub max_bytes: usize,
    /// Persistence requests will be throttled to this. Requests received early will be delayed.
    pub repeat_seconds: i64,
}

const CONFIG_GLOB: &str = "/config/data/*.persist";

lazy_static! {
    static ref NAME_VALIDATOR: Regex = Regex::new(r"^[a-z][a-z-]*$").unwrap();
}

fn validate_name(tag: &str) -> Result<(), Error> {
    if !NAME_VALIDATOR.is_match(tag) {
        bail!("Invalid tag {} must match [a-z][a-z-]*", tag);
    }
    Ok(())
}

pub fn try_insert_items(config: &mut Config, config_text: &str) -> Result<(), Error> {
    let items = serde_json5::from_str::<Vec<TaggedPersist>>(config_text)?;
    for item in items.into_iter() {
        validate_name(&item.tag)?;
        validate_name(&item.service_name)?;
        if let Some(tagged_persist) = config
            .entry(item.service_name.clone())
            .or_insert_with(|| HashMap::new())
            .insert(item.tag.clone(), item)
        {
            bail!("Duplicate TaggedPersist found: {:?}", tagged_persist);
        }
    }
    Ok(())
}

pub fn load_configuration_files() -> Result<Config, Error> {
    let mut config = HashMap::new();
    for file_path in glob(CONFIG_GLOB)? {
        try_insert_items(&mut config, &std::fs::read_to_string(file_path?)?)?;
    }
    Ok(config)
}

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

    #[test]
    fn verify_insert_logic() {
        let mut config = HashMap::new();
        let taga_servab = "[{tag: 'tag-a', service_name: 'serv-a', max_bytes: 10, \
                           repeat_seconds: 31, selectors: ['foo', 'bar']}, \
                           {tag: 'tag-a', service_name: 'serv-b', max_bytes: 20, \
                           repeat_seconds: 32, selectors: ['baz']}, ]";
        let tagb_servb = "[{tag: 'tag-b', service_name: 'serv-b', max_bytes: 30, \
                          repeat_seconds: 33, selectors: ['quux']}]";
        // Numbers not allowed in names
        let bad_tag = "[{tag: 'tag-b1', service_name: 'serv-b', max_bytes: 30, \
                       repeat_seconds: 33, selectors: ['quux']}]";
        // Underscores not allowed in names
        let bad_serv = "[{tag: 'tag-b', service_name: 'serv_b', max_bytes: 30, \
                        repeat_seconds: 33, selectors: ['quux']}]";
        let persist_aa = TaggedPersist {
            tag: "tag-a".to_string(),
            service_name: "serv-a".to_string(),
            max_bytes: 10,
            repeat_seconds: 31,
            selectors: vec!["foo".to_string(), "bar".to_string()],
        };
        let persist_ba = TaggedPersist {
            tag: "tag-a".to_string(),
            service_name: "serv-b".to_string(),
            max_bytes: 20,
            repeat_seconds: 32,
            selectors: vec!["baz".to_string()],
        };
        let persist_bb = TaggedPersist {
            tag: "tag-b".to_string(),
            service_name: "serv-b".to_string(),
            max_bytes: 30,
            repeat_seconds: 33,
            selectors: vec!["quux".to_string()],
        };

        assert!(try_insert_items(&mut config, taga_servab).is_ok());
        assert!(try_insert_items(&mut config, tagb_servb).is_ok());
        assert_eq!(config.len(), 2);
        let service_a = config.get("serv-a").unwrap();
        assert_eq!(service_a.len(), 1);
        assert_eq!(service_a.get("tag-a"), Some(&persist_aa));
        let service_b = config.get("serv-b").unwrap();
        assert_eq!(service_b.len(), 2);
        assert_eq!(service_b.get("tag-a"), Some(&persist_ba));
        assert_eq!(service_b.get("tag-b"), Some(&persist_bb));

        assert!(try_insert_items(&mut config, bad_tag).is_err());
        assert!(try_insert_items(&mut config, bad_serv).is_err());
        // Can't duplicate tags in the same service
        assert!(try_insert_items(&mut config, tagb_servb).is_err());
    }
}