//! The plug-in manifest (`vc_manifest`) and parameter schema.

use serde::{Deserialize, Serialize};
use serde_json::{Map, Value, json};

use crate::{Error, Result};

/// Longest manifest the host reads.
pub const MAX_MANIFEST_BYTES: usize = 64 * 1024;
/// Most parameters a plug-in may declare.
pub const MAX_PARAMS: usize = 64;

/// What a plug-in is.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum Kind {
    /// An object filter: reads the selected paths and returns the objects to keep, change or add
    /// (Object › Plug-ins, `plugin.run`).
    Filter,
    /// A live effect: rewrites one object's geometry each time it is drawn, from its appearance
    /// stack (Effect › Plug-ins, `effect.apply`).
    Effect,
}

impl Kind {
    pub fn name(self) -> &'static str {
        match self {
            Kind::Filter => "filter",
            Kind::Effect => "effect",
        }
    }
}

/// One declared parameter.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "camelCase")]
pub enum ParamSpec {
    /// A real number in `min..=max`.
    Number { min: f64, max: f64, default: f64 },
    /// A whole number in `min..=max`.
    Int {
        #[serde(default = "int_min")]
        min: i64,
        #[serde(default = "int_max")]
        max: i64,
        #[serde(default)]
        default: i64,
    },
    /// A checkbox.
    Bool {
        #[serde(default)]
        default: bool,
    },
    /// One of `options` (a dropdown).
    Choice {
        options: Vec<String>,
        #[serde(default)]
        default: Option<String>,
    },
}

fn int_min() -> i64 {
    -1_000_000
}
fn int_max() -> i64 {
    1_000_000
}

impl ParamSpec {
    /// The value a parameter takes when it isn't given.
    pub fn default_value(&self) -> Value {
        match self {
            ParamSpec::Number { default, .. } => json!(default),
            ParamSpec::Int { default, .. } => json!(default),
            ParamSpec::Bool { default } => json!(default),
            ParamSpec::Choice { options, default } => json!(default.clone().or_else(|| options.first().cloned()).unwrap_or_default()),
        }
    }
}

/// The manifest a plug-in returns from `vc_manifest` (UTF-8 JSON).
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Manifest {
    /// Stable id, `[A-Za-z0-9._-]{1,64}` (reverse-DNS style is recommended: `org.example.tidy`).
    pub id: String,
    /// Menu label.
    pub name: String,
    #[serde(default)]
    pub version: String,
    pub kind: Kind,
    #[serde(default)]
    pub description: String,
    #[serde(default)]
    pub author: String,
    /// Parameters in declaration (dialog) order; a JSON object `{"name": spec, …}` in the manifest.
    #[serde(default, deserialize_with = "ordered_params", serialize_with = "params_as_object")]
    pub params: Vec<(String, ParamSpec)>,
}

impl Manifest {
    /// Parses and validates manifest JSON.
    pub fn parse(bytes: &[u8]) -> Result<Manifest> {
        if bytes.len() > MAX_MANIFEST_BYTES {
            return Err(Error::Manifest(format!("manifest is {} bytes (limit {MAX_MANIFEST_BYTES})", bytes.len())));
        }
        let text = std::str::from_utf8(bytes).map_err(|_| Error::Manifest("manifest is not UTF-8".into()))?;
        let man: Manifest = serde_json::from_str(text).map_err(|e| Error::Manifest(format!("manifest: {e}")))?;
        man.validate()?;
        Ok(man)
    }

    /// The manifest of a module still being loaded.
    pub(crate) fn placeholder() -> Manifest {
        Manifest {
            id: String::new(),
            name: String::new(),
            version: String::new(),
            kind: Kind::Filter,
            description: String::new(),
            author: String::new(),
            params: Vec::new(),
        }
    }

    fn validate(&self) -> Result<()> {
        if !valid_id(&self.id) {
            return Err(Error::Manifest(format!("invalid id {:?}: use 1-64 characters from A-Z a-z 0-9 . _ -", self.id)));
        }
        let name = self.name.trim();
        if name.is_empty() || name.chars().count() > 64 || name.chars().any(char::is_control) {
            return Err(Error::Manifest("`name` must be 1-64 printable characters".into()));
        }
        if self.version.len() > 32 || self.description.len() > 1024 || self.author.len() > 128 {
            return Err(Error::Manifest("`version`, `description` or `author` is too long".into()));
        }
        for (k, spec) in &self.params {
            if !valid_key(k) {
                return Err(Error::Manifest(format!("invalid parameter name {k:?}")));
            }
            match spec {
                ParamSpec::Number { min, max, default } if !(min.is_finite() && max.is_finite() && default.is_finite()) || min > max => {
                    return Err(Error::Manifest(format!("parameter `{k}`: bad range")));
                }
                ParamSpec::Int { min, max, .. } if min > max => return Err(Error::Manifest(format!("parameter `{k}`: bad range"))),
                ParamSpec::Choice { options, default } => {
                    if options.is_empty()
                        || options.len() > 64
                        || options.iter().any(|o| o.is_empty() || o.len() > 64 || o.chars().any(char::is_control))
                    {
                        return Err(Error::Manifest(format!("parameter `{k}`: choices must be 1-64 non-empty, printable strings")));
                    }
                    if default.as_ref().is_some_and(|d| !options.contains(d)) {
                        return Err(Error::Manifest(format!("parameter `{k}`: default is not one of the options")));
                    }
                }
                _ => {}
            }
        }
        Ok(())
    }

    /// The parameters documented the way command and effect parameters are
    /// (`{amount: 0..100 (50), mode: "soft"|"hard" (soft), mono: bool (false)}`).
    pub fn params_doc(&self) -> String {
        let parts: Vec<String> = self
            .params
            .iter()
            .map(|(k, spec)| match spec {
                ParamSpec::Number { min, max, default } => format!("{k}: {min}..{max} ({default})"),
                ParamSpec::Int { min, max, default } => format!("{k}: int {min}..{max} ({default})"),
                ParamSpec::Bool { default } => format!("{k}: bool ({default})"),
                ParamSpec::Choice { options, .. } => {
                    let opts: Vec<String> = options.iter().map(|o| format!("{o:?}")).collect();
                    format!("{k}: {} ({})", opts.join("|"), spec.default_value().as_str().unwrap_or_default())
                }
            })
            .collect();
        format!("{{{}}}", parts.join(", "))
    }

    /// Every parameter at its default value.
    pub fn defaults(&self) -> Map<String, Value> {
        self.params.iter().map(|(k, spec)| (k.clone(), spec.default_value())).collect()
    }

    /// Validates user `params` against the schema: missing keys take their defaults, numbers are
    /// clamped into range (whole numbers rounded), unknown keys are dropped; a value of the wrong
    /// type is an error.
    pub fn resolve_params(&self, params: &Value) -> Result<Map<String, Value>> {
        let given = match params {
            Value::Null => &Map::new(),
            Value::Object(m) => m,
            _ => return Err(Error::Params("plug-in parameters must be a JSON object".into())),
        };
        let mut out = Map::new();
        for (k, spec) in &self.params {
            let Some(v) = given.get(k).filter(|v| !v.is_null()) else {
                out.insert(k.clone(), spec.default_value());
                continue;
            };
            let wrong = |what: &str| Error::Params(format!("`{k}` must be {what}"));
            let resolved = match spec {
                ParamSpec::Number { min, max, .. } => json!(v.as_f64().filter(|f| f.is_finite()).ok_or_else(|| wrong("a number"))?.clamp(*min, *max)),
                ParamSpec::Int { min, max, .. } => {
                    // Keep JSON integers exact: f64 cannot represent every i64 or its bounds.
                    let value = if let Some(i) = v.as_i64() {
                        i.clamp(*min, *max)
                    } else if v.is_u64() {
                        // Past i64::MAX, so past any maximum.
                        *max
                    } else {
                        let f = v.as_f64().filter(|f| f.is_finite()).ok_or_else(|| wrong("a number"))?;
                        (f.round() as i64).clamp(*min, *max)
                    };
                    json!(value)
                }
                ParamSpec::Bool { .. } => json!(v.as_bool().ok_or_else(|| wrong("true or false"))?),
                ParamSpec::Choice { options, .. } => {
                    let s = v.as_str().ok_or_else(|| wrong("a string"))?;
                    if !options.iter().any(|o| o == s) {
                        return Err(Error::Params(format!("`{k}` must be one of {}", options.join(", "))));
                    }
                    json!(s)
                }
            };
            out.insert(k.clone(), resolved);
        }
        Ok(out)
    }
}

/// Reads the `params` object keeping its key order (serde_json's `Map` would sort it).
fn ordered_params<'de, D: serde::Deserializer<'de>>(d: D) -> std::result::Result<Vec<(String, ParamSpec)>, D::Error> {
    struct V;
    impl<'de> serde::de::Visitor<'de> for V {
        type Value = Vec<(String, ParamSpec)>;
        fn expecting(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
            f.write_str("an object of parameter specs")
        }
        fn visit_unit<E: serde::de::Error>(self) -> std::result::Result<Self::Value, E> {
            Ok(Vec::new())
        }
        fn visit_map<A: serde::de::MapAccess<'de>>(self, mut map: A) -> std::result::Result<Self::Value, A::Error> {
            let mut out: Vec<(String, ParamSpec)> = Vec::new();
            while let Some((k, v)) = map.next_entry::<String, ParamSpec>()? {
                if out.len() >= MAX_PARAMS {
                    return Err(serde::de::Error::custom(format!("too many parameters (limit {MAX_PARAMS})")));
                }
                if out.iter().any(|(o, _)| *o == k) {
                    return Err(serde::de::Error::custom(format!("parameter `{k}` is declared twice")));
                }
                out.push((k, v));
            }
            Ok(out)
        }
    }
    d.deserialize_any(V)
}

fn params_as_object<S: serde::Serializer>(p: &[(String, ParamSpec)], s: S) -> std::result::Result<S::Ok, S::Error> {
    use serde::ser::SerializeMap;
    let mut m = s.serialize_map(Some(p.len()))?;
    for (k, v) in p {
        m.serialize_entry(k, v)?;
    }
    m.end()
}

/// `[A-Za-z0-9._-]{1,64}`.
pub fn valid_id(id: &str) -> bool {
    (1..=64).contains(&id.len()) && id.bytes().all(|b| b.is_ascii_alphanumeric() || matches!(b, b'.' | b'_' | b'-'))
}

/// `[A-Za-z0-9_]{1,64}`, not starting with `_` and not a key the commands and dialogs use
/// themselves.
fn valid_key(k: &str) -> bool {
    (1..=64).contains(&k.len())
        && k.bytes().all(|b| b.is_ascii_alphanumeric() || b == b'_')
        && !k.starts_with('_')
        && !matches!(k, "id" | "ids" | "params" | "preview")
}

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

    const FULL: &str = r#"{"id":"org.example.tone","name":"Tone","version":"1.2","kind":"effect",
        "params":{"amount":{"type":"number","min":0,"max":100,"default":50},
                  "mode":{"type":"choice","options":["soft","hard"],"default":"hard"},
                  "mono":{"type":"bool"},"seed":{"type":"int","min":0,"max":9}}}"#;

    #[test]
    fn parses_and_keeps_param_order() {
        let m = Manifest::parse(FULL.as_bytes()).unwrap();
        assert_eq!(m.id, "org.example.tone");
        assert_eq!(m.kind, Kind::Effect);
        assert_eq!(m.params.iter().map(|p| p.0.as_str()).collect::<Vec<_>>(), ["amount", "mode", "mono", "seed"]);
        assert_eq!(m.params_doc(), r#"{amount: 0..100 (50), mode: "soft"|"hard" (hard), mono: bool (false), seed: int 0..9 (0)}"#);
        assert_eq!(Value::Object(m.defaults()), json!({"amount": 50.0, "mode": "hard", "mono": false, "seed": 0}));
    }

    #[test]
    fn resolves_defaults_clamps_and_rejects_wrong_types() {
        let m = Manifest::parse(FULL.as_bytes()).unwrap();
        let p = m.resolve_params(&json!({"amount": 500, "seed": 3.6, "junk": 1})).unwrap();
        assert_eq!(Value::Object(p), json!({"amount": 100.0, "mode": "hard", "mono": false, "seed": 4}));
        assert!(m.resolve_params(&json!({"amount": "lots"})).is_err());
        assert!(m.resolve_params(&json!({"mode": "medium"})).is_err());
        assert!(m.resolve_params(&json!({"mono": 1})).is_err());
        assert!(m.resolve_params(&json!([1, 2])).is_err());
        assert!(m.resolve_params(&Value::Null).is_ok());
    }

    #[test]
    fn integer_parameters_preserve_precision_and_exact_bounds() {
        let m = Manifest::parse(
            br#"{"id":"org.example.generative","name":"Generative Pattern","kind":"filter",
                "params":{"seed":{"type":"int","min":-9007199254740995,"max":9007199254740995}}}"#,
        )
        .unwrap();
        for (given, expected) in [
            (json!(9007199254740992_i64), 9007199254740992_i64),
            (json!(9007199254740993_i64), 9007199254740993_i64),
            (json!(-9007199254740993_i64), -9007199254740993_i64),
            (json!(i64::MAX), 9007199254740995_i64),
            (json!(i64::MIN), -9007199254740995_i64),
            (json!(u64::MAX), 9007199254740995_i64),
            (json!(1e30), 9007199254740995_i64),
            (json!(-1e30), -9007199254740995_i64),
            (json!(3.6), 4_i64),
        ] {
            let resolved = m.resolve_params(&json!({"seed": given})).unwrap();
            assert_eq!(resolved["seed"], json!(expected), "input: {given}");
        }
    }

    #[test]
    fn rejects_bad_manifests() {
        for bad in [
            "",
            "[]",
            "not json",
            r#"{"id":"","name":"x","kind":"filter"}"#,
            r#"{"id":"a b","name":"x","kind":"filter"}"#,
            r#"{"id":"a","name":"","kind":"filter"}"#,
            r#"{"id":"a","name":"x","kind":"panel"}"#,
            r#"{"id":"a","name":"x"}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":{"r":{"type":"number","min":5,"max":1,"default":1}}}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":{"c":{"type":"choice","options":[]}}}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":{"__x":{"type":"bool"}}}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":{"preview":{"type":"bool"}}}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":{"a":{"type":"bool"},"a":{"type":"bool"}}}"#,
            r#"{"id":"a","name":"x","kind":"filter","params":[1]}"#,
        ] {
            assert!(Manifest::parse(bad.as_bytes()).is_err(), "{bad}");
        }
        assert!(Manifest::parse(&[0xff, 0xfe]).is_err());
        assert!(Manifest::parse(&vec![b' '; MAX_MANIFEST_BYTES + 1]).is_err());
    }
}