//! The SolveCraft engine.
//!
//! Every user-visible action is a command with a stable id. Ids are Fusion's command ids where
//! Fusion has the command (`Extrude`, `SketchCreate`, `FusionFilletEdgesCommand`…) and dotted
//! lower-case ids otherwise (`timeline.rollback`, `document.inspect`). Commands take JSON
//! parameters and never open dialogs; the UI, the command palette, scripts, the CLI and the
//! control channel all run the same commands through [`Session::execute`].
#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
#![forbid(unsafe_code)]

pub mod cmd;
pub mod params;
pub mod view;

use std::sync::Arc;

use serde::{Deserialize, Serialize};
use serde_json::Value;
use solvecraft_doc::{Document, Model};
use solvecraft_geom::Vec3;

pub use cmd::{CommandInfo, CommandSpec, command_specs, find_command};
pub use solvecraft_doc as doc;
pub use solvecraft_geom as geom;
pub use solvecraft_io as io;
pub use solvecraft_kernel as kernel;
pub use solvecraft_render as render;
pub use solvecraft_sketch as sketch;

#[derive(Debug, thiserror::Error)]
pub enum EngineError {
    #[error("unknown command `{0}`")]
    UnknownCommand(String),
    #[error("`{0}` is not available right now: {1}")]
    Disabled(String, String),
    #[error("invalid parameters for `{cmd}`: {msg}")]
    BadParams { cmd: String, msg: String },
    #[error("{0}")]
    Other(String),
    /// A command panicked; the document was kept as it was (a bug: please report it).
    #[error("internal error in `{0}` (the design was kept as it was): {1}")]
    Internal(String, String),
}

impl From<solvecraft_doc::DocError> for EngineError {
    fn from(e: solvecraft_doc::DocError) -> Self {
        EngineError::Other(e.to_string())
    }
}
impl From<solvecraft_sketch::SketchError> for EngineError {
    fn from(e: solvecraft_sketch::SketchError) -> Self {
        EngineError::Other(e.to_string())
    }
}
impl From<solvecraft_kernel::KernelError> for EngineError {
    fn from(e: solvecraft_kernel::KernelError) -> Self {
        EngineError::Other(e.to_string())
    }
}
impl From<solvecraft_io::IoError> for EngineError {
    fn from(e: solvecraft_io::IoError) -> Self {
        EngineError::Other(e.to_string())
    }
}

pub type Result<T> = std::result::Result<T, EngineError>;

/// Something selected in the model.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum Sel {
    Body {
        name: String,
    },
    /// An edge, identified by a point on it.
    Edge {
        body: String,
        index: usize,
        point: Vec3,
    },
    Face {
        body: String,
        index: usize,
        point: Vec3,
    },
    Feature {
        id: u64,
    },
    /// A sketch curve or point (by id) of the active sketch.
    SketchCurve {
        id: String,
    },
    SketchPoint {
        id: String,
    },
    /// A closed profile of a sketch (by index).
    Profile {
        sketch: u64,
        index: usize,
    },
}

/// One undo step.
#[derive(Clone, Debug)]
pub struct Snapshot {
    pub label: String,
    pub doc: Arc<Document>,
    pub active_sketch: Option<u64>,
}

/// An editing session on one design.
pub struct Session {
    pub doc: Arc<Document>,
    pub model: Model,
    pub undo: Vec<Snapshot>,
    pub redo: Vec<Snapshot>,
    /// Sketch feature being edited (sketch mode).
    pub active_sketch: Option<u64>,
    pub selection: Vec<Sel>,
    pub path: Option<String>,
    saved: Arc<Document>,
    /// Messages for the command line / log.
    pub log: Vec<String>,
    /// Increments on every document change (views use it to refresh).
    pub revision: u64,
}

const MAX_UNDO: usize = 200;
const MAX_LOG: usize = 2000;

impl Default for Session {
    fn default() -> Self {
        Session::new(Document::new("Untitled"))
    }
}

impl Session {
    pub fn new(doc: Document) -> Self {
        let doc = Arc::new(doc);
        let mut model = Model::new();
        model.evaluate(&doc);
        Session {
            saved: doc.clone(),
            doc,
            model,
            undo: Vec::new(),
            redo: Vec::new(),
            active_sketch: None,
            selection: Vec::new(),
            path: None,
            log: Vec::new(),
            revision: 1,
        }
    }

    pub fn is_dirty(&self) -> bool {
        !Arc::ptr_eq(&self.doc, &self.saved) && *self.doc != *self.saved
    }
    pub fn mark_saved(&mut self) {
        self.saved = self.doc.clone();
    }

    pub fn echo(&mut self, s: impl Into<String>) {
        self.log.push(s.into());
        if self.log.len() > MAX_LOG {
            let n = self.log.len() - MAX_LOG;
            self.log.drain(..n);
        }
    }

    /// Mutable document (copy-on-write).
    pub fn doc_mut(&mut self) -> &mut Document {
        Arc::make_mut(&mut self.doc)
    }

    /// Re-evaluate the model after a document change.
    pub fn refresh(&mut self) {
        self.model.evaluate(&self.doc);
        self.revision += 1;
        if let Some(id) = self.active_sketch
            && self.doc.feature(id).is_none()
        {
            self.active_sketch = None;
        }
    }

    /// Run a command with JSON parameters (no dialogs). Undoable commands record an undo step
    /// when they change the document; a failing or panicking command leaves it unchanged.
    pub fn execute(&mut self, id: &str, params: &Value) -> Result<Value> {
        let spec = find_command(id).ok_or_else(|| EngineError::UnknownCommand(id.to_string()))?;
        (spec.enabled)(self).map_err(|why| EngineError::Disabled(spec.id.to_string(), why))?;
        let before = Snapshot { label: spec.label.to_string(), doc: self.doc.clone(), active_sketch: self.active_sketch };
        let null = Value::Object(Default::default());
        let params = if params.is_null() { &null } else { params };
        let r = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| (spec.run)(self, params)));
        let r = match r {
            Ok(r) => r,
            Err(p) => {
                let msg = p.downcast_ref::<&str>().map(|s| s.to_string()).or_else(|| p.downcast_ref::<String>().cloned()).unwrap_or_default();
                Err(EngineError::Internal(spec.id.to_string(), msg))
            }
        };
        let changed = !Arc::ptr_eq(&self.doc, &before.doc);
        match r {
            Ok(v) => {
                if changed {
                    if spec.undoable {
                        self.undo.push(before);
                        if self.undo.len() > MAX_UNDO {
                            self.undo.remove(0);
                        }
                        self.redo.clear();
                    }
                    self.refresh();
                }
                Ok(v)
            }
            Err(e) => {
                if changed {
                    self.doc = before.doc;
                    self.active_sketch = before.active_sketch;
                    self.refresh();
                }
                Err(e)
            }
        }
    }

    /// Run a script: a JSON array of `{"command": id, "params": {...}}` (or an object with a
    /// `commands` array). Stops at the first error. Returns each command's result.
    pub fn run_script(&mut self, script: &Value) -> Result<Vec<Value>> {
        let list = match script {
            Value::Array(a) => a.clone(),
            Value::Object(o) => {
                o.get("commands").and_then(Value::as_array).cloned().ok_or_else(|| EngineError::Other("script: missing `commands` array".into()))?
            }
            _ => return Err(EngineError::Other("script must be a JSON array or {\"commands\": [...]}".into())),
        };
        if list.len() > 100_000 {
            return Err(EngineError::Other("script too long".into()));
        }
        let mut out = Vec::new();
        for (i, c) in list.iter().enumerate() {
            let id = c
                .get("command")
                .or_else(|| c.get("id"))
                .and_then(Value::as_str)
                .ok_or_else(|| EngineError::Other(format!("script step {}: missing `command`", i + 1)))?;
            let p = c.get("params").cloned().unwrap_or(Value::Null);
            let r = self.execute(id, &p).map_err(|e| EngineError::Other(format!("step {} ({id}): {e}", i + 1)))?;
            out.push(r);
        }
        Ok(out)
    }
}

#[cfg(test)]
mod tests;