//! Model project roadmaps and step dependencies
//!
//! This crate models a roadmap as steps, which may depend on each
//! other, and a directed acyclic graph (DAG) of said steps, which
//! leads to the end goal. There is no support for due dates,
//! estimates, or other such project management features. These roadmaps only
//! care about what steps need to be take, in what order, to reach the
//! goal.
//!
//! # Example
//! ```
//! # use roadmap::Step;
//! # fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
//! let mut r = roadmap::Roadmap::from_yaml("
//! endgoal:
//!   label: The end goal
//!   depends:
//!   - first
//! first:
//!   label: The first step
//! ").unwrap();
//!
//! let n = r.step_names();
//! assert_eq!(n.len(), 2);
//! assert!(n.contains(&"first"));
//! assert!(n.contains(&"endgoal"));
//!
//! r.set_missing_statuses();
//! println!("{}", r.as_dot(30).unwrap());
//!
//! # Ok(())
//! # }
//! ```

use serde_yaml;
use serde_yaml::Value;
use std::collections::HashMap;
use std::error::Error;
use textwrap::fill;

#[derive(Clone,Debug,PartialEq)]
pub enum Status {
    Unknown,
    Goal,
    Finished,
    Ready,
    Next,
    Blocked,
}

impl Status {
    fn from(text: &str) -> Option<Status> {
        match text {
            "" => Some(Status::Unknown),
            "goal" => Some(Status::Goal),
            "finished" => Some(Status::Finished),
            "ready" => Some(Status::Ready),
            "next" => Some(Status::Next),
            "blocked" => Some(Status::Blocked),
            _ => None,
        }
    }
}

impl PartialEq<Status> for &Status {
    fn eq(&self, other: &Status) -> bool {
        **self == *other
    }
}

impl PartialEq<&Status> for Status {
    fn eq(&self, other: &&Status) -> bool {
        **other == *self
    }
}

/// A step in a roadmap.
#[derive(Clone, Debug, PartialEq)]
pub struct Step {
    name: String,
    status: Status,
    label: String,
    depends: Vec<String>,
}

impl Step {
    /// Create a new step with a name and a label.
    pub fn new(name: &str, label: &str) -> Step {
        Step {
            name: name.to_string(),
            status: Status::Unknown,
            label: label.to_string(),
            depends: vec![],
        }
    }

    /// Return the name of a step.
    pub fn name<'a>(&'a self) -> &'a str {
        &self.name
    }

    /// Return the label of a step.
    pub fn label<'a>(&'a self) -> &'a str {
        &self.label
    }

    /// Return the status of a step.
    pub fn status<'a>(&'a self) -> &Status {
        &self.status
    }

    /// Set the status of a step.
    pub fn set_status(&mut self, status: Status) {
        self.status = status
    }

    /// Return vector of names of dependencies for a step.
    pub fn dependencies(&self) -> impl Iterator<Item = &String> {
        self.depends.iter()
    }

    /// Add the name of a dependency to step.
    pub fn add_dependency(&mut self, name: &str) {
        self.depends.push(String::from(name));
    }

    /// Does this step depend on given other step?
    pub fn depends_on(&self, other_name: &str) -> bool {
        self.depends.iter().any(|depname| depname == other_name)
    }
}

/// Result type for roadmap parsing.
type ParseResult<T> = Result<T, String>;

/// All the steps to get to the end goal.
pub struct Roadmap {
    steps: Vec<Step>,
}

impl Roadmap {
    /// Create a new, empty roadmap.
    pub fn new() -> Roadmap {
        Roadmap { steps: vec![] }
    }

    /// Create a new roadmap from a YAML representation.
    pub fn from_yaml(yaml: &str) -> Result<Roadmap, Box<dyn Error>> {
        let mut roadmap = Roadmap::new();
        let map: HashMap<String, serde_yaml::Value> = serde_yaml::from_str(yaml)?;

        for (name, value) in map {
            let step = Roadmap::step_from_value(&name, &value)?;
            roadmap.add_step(&step)?;
        }

        roadmap.validate()?;
        Ok(roadmap)
    }

    // Convert a Value into a Step, if possible.
    fn step_from_value(name: &str, value: &Value) -> ParseResult<Step> {
        match value {
            Value::Mapping(_) => {
                let label = Roadmap::parse_label(&value);
                let mut step = Step::new(name, label);

                let status = Roadmap::parse_status(&value)?;
                step.set_status(status);

                for depname in Roadmap::parse_depends(&value).iter() {
                    step.add_dependency(depname);
                }

                Ok(step)
            }
            _ => Err("step is not a mapping".to_string()),
        }
    }

    // Get a sequence of depenencies.
    fn parse_depends(map: &Value) -> Vec<&str> {
        let key_name = "depends";
        let key = Value::String(key_name.to_string());
        let mut depends: Vec<&str> = vec![];

        if let Some(Value::Sequence(deps)) = map.get(&key) {
            for depname in deps.iter() {
                if let Value::String(depname) = depname {
                    depends.push(depname);
                }
            }
        }

        depends
    }

    // Get label string from a Mapping element, or empty string.
    fn parse_label<'a>(map: &'a Value) -> &'a str {
        Roadmap::parse_string("label", map)
    }

    // Get status string from a Mapping element. Default to unknown status.
    fn parse_status<'a>(map: &'a Value) -> ParseResult<Status> {
        let status_text = Roadmap::parse_string("status", map);
        let status = Status::from(status_text);
        if let Some(status) = status {
            Ok(status)
        } else {
            Err(format!("unknown status: {:?}", status_text))
        }
    }

    // Get string value from a Mapping element, or empty string.
    fn parse_string<'a>(key_name: &str, map: &'a Value) -> &'a str {
        let key = Value::String(key_name.to_string());
        match map.get(&key) {
            Some(Value::String(s)) => s,
            _ => "",
        }
    }

    // Validate that the parsed, constructed roadmap is valid.
    fn validate(&self) -> ParseResult<()> {
        // Is there exactly one goal?
        if self.count_goals() != 1 {
            return Err(format!("must have exactly one goal for roadmap"));
        }

        // Does every dependency exist?
        for step in self.steps.iter() {
            for depname in step.dependencies() {
                match self.get_step(depname) {
                    None => {
                        return Err(format!(
                            "step {} depends on missing {}",
                            step.name(),
                            depname
                        ))
                    }
                    Some(_) => (),
                }
            }
        }

        Ok(())
    }

    // Count number of steps that nothing depends on.
    fn count_goals(&self) -> usize {
        self.steps
            .iter()
            .map(|step| self.is_goal(step))
            .filter(|b| *b)
            .count()
    }

    /// Return list of step names.
    pub fn step_names<'a>(&'a self) -> Vec<&'a str> {
        let mut names = vec![];
        for step in self.steps.iter() {
            names.push(step.name());
        }
        names
    }

    /// Get a step, given its name.
    pub fn get_step<'a>(&'a self, name: &str) -> Option<&'a Step> {
        for step in self.steps.iter() {
            if step.name() == name {
                return Some(step);
            }
        }
        None
    }

    /// Add a step to the roadmap. This may fail, if there's a step
    /// with that name already.
    pub fn add_step(&mut self, step: &Step) -> Result<(), Box<dyn std::error::Error>> {
        self.steps.push(step.clone());
        Ok(())
    }

    // Get iterator over refs to steps.
    pub fn iter(&self) -> impl Iterator<Item = &Step> {
        self.steps.iter()
    }

    // Get iterator over mut refs to steps.
    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut Step> {
        self.steps.iter_mut()
    }

    /// Compute status of any step for which it has not been specified
    /// in the input.
    pub fn set_missing_statuses(&mut self) {
        let new_steps: Vec<Step> = self
            .steps
            .iter()
            .map(|step| {
                let mut step = step.clone();
                if self.is_unset(&step) {
                    if self.is_goal(&step) {
                        step.set_status(Status::Goal);
                    } else if self.is_blocked(&step) {
                        step.set_status(Status::Blocked);
                    } else if self.is_ready(&step) {
                        step.set_status(Status::Ready);
                    }
                }
                step
            })
            .collect();

        if self.steps != new_steps {
            self.steps = new_steps;
            self.set_missing_statuses();
        }
    }

    // Is status unset?
    fn is_unset(&self, step: &Step) -> bool {
        step.status() == Status::Unknown
    }

    // Should unset status be ready? In other words, if there are any
    // dependencies, they are all finished.
    fn is_ready(&self, step: &Step) -> bool {
        self.dep_statuses(step)
            .iter()
            .all(|&status| status == Status::Finished)
    }

    // Should unset status be blocked? In other words, if there are
    // any dependencies, that aren't finished.
    fn is_blocked(&self, step: &Step) -> bool {
        self.dep_statuses(step)
            .iter()
            .any(|&status| status != Status::Finished)
    }

    // Return vector of all statuses of all dependencies
    fn dep_statuses<'a>(&'a self, step: &Step) -> Vec<&Status> {
        step.dependencies()
            .map(|depname| {
                if let Some(step) = self.get_step(depname) {
                    step.status()
                } else {
                    &Status::Unknown
                }
            })
            .collect()
    }

    // Should status be goal? In other words, does any other step
    // depend on this one?
    fn is_goal(&self, step: &Step) -> bool {
        let has_parent = self.steps.iter().any(|other| other.depends_on(step.name()));
        !has_parent
    }

    /// Get a Graphviz dot language representation of a roadmap. This
    /// is the textual representation, and the caller needs to use the
    /// Graphviz dot(1) tool to create an image from it.
    pub fn as_dot(self, label_width: usize) -> Result<String, Box<dyn std::error::Error>> {
        let labels = self.steps.iter().map(|step| {
            format!(
                "{} [label=\"{}\" style=filled fillcolor=\"{}\" shape=\"{}\"];\n",
                step.name(),
                fill(&step.label(), label_width).replace("\n", "\\n"),
                Roadmap::get_status_color(step),
                Roadmap::get_status_shape(step),
            )
        });

        let mut dot = String::new();
        dot.push_str("digraph \"roadmap\" {\n");
        for line in labels {
            dot.push_str(&line);
        }

        for step in self.iter() {
            for dep in step.dependencies() {
                let line = format!("{} -> {};\n", dep, step.name());
                dot.push_str(&line);
            }
        }

        dot.push_str("}\n");

        Ok(dot)
    }

    fn get_status_color(step: &Step) -> &str {
        match step.status() {
            Status::Blocked => "#f4bada",
            Status::Finished => "#eeeeee",
            Status::Ready => "#ffffff",
            Status::Next => "#0cc00",
            Status::Goal => "#00eeee",
            Status::Unknown => "#rr0000",
        }
    }

    fn get_status_shape(step: &Step) -> &str {
        match step.status() {
            Status::Blocked => "rectangle",
            Status::Finished => "circle",
            Status::Ready => "ellipse",
            Status::Next => "ellipse",
            Status::Goal => "diamond",
            Status::Unknown => "house",
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{Roadmap, Step, Status};

    #[test]
    fn new_step() {
        let step = Step::new("myname", "my label");
        assert_eq!(step.name(), "myname");
        assert_eq!(step.status(), Status::Unknown);
        assert_eq!(step.label(), "my label");
        assert_eq!(step.dependencies().count(), 0);
    }

    #[test]
    fn set_status() {
        let mut step = Step::new("myname", "my label");
        step.set_status(Status::Next);
        assert_eq!(step.status(), Status::Next);
    }

    #[test]
    fn add_step_dependency() {
        let mut second = Step::new("second", "the second step");
        second.add_dependency("first");
        let deps: Vec<&String> = second.dependencies().collect();
        assert_eq!(deps, vec!["first"]);
    }

    #[test]
    fn new_roadmap() {
        let roadmap = Roadmap::new();
        assert_eq!(roadmap.step_names().len(), 0);
    }

    #[test]
    fn add_step_to_roadmap() {
        let mut roadmap = Roadmap::new();
        let first = Step::new("first", "the first step");
        roadmap.add_step(&first).unwrap();
        assert_eq!(roadmap.step_names().len(), 1);
        assert_eq!(roadmap.step_names(), vec!["first"]);
    }

    #[test]
    fn get_step_from_roadmap() {
        let mut roadmap = Roadmap::new();
        let first = Step::new("first", "the first step");
        roadmap.add_step(&first).unwrap();
        let gotit = roadmap.get_step("first").unwrap();
        assert_eq!(gotit.name(), "first");
        assert_eq!(gotit.label(), "the first step");
    }

    #[test]
    fn parse_yaml_is_list() {
        let r = Roadmap::from_yaml("[]");
        match r {
            Ok(_) => panic!("expected a parse error"),
            _ => (),
        }
    }

    #[test]
    fn parse_yaml_is_empty() {
        let r = Roadmap::from_yaml("");
        match r {
            Ok(_) => panic!("expected a parse error"),
            _ => (),
        }
    }

    #[test]
    fn parse_yaml_map_entries_not_maps() {
        let r = Roadmap::from_yaml("foo: []");
        match r {
            Ok(_) => panic!("expected a parse error"),
            _ => (),
        }
    }

    #[test]
    fn parse_yaml_unknown_dep() {
        let r = Roadmap::from_yaml("foo: {depends: [bar]}");
        match r {
            Ok(_) => panic!("expected a parse error"),
            _ => (),
        }
    }

    #[test]
    fn parse_yaml_unknown_status() {
        let r = Roadmap::from_yaml(r#"foo: {status: "bar"}"#);
        match r {
            Ok(_) => panic!("expected a parse error"),
            _ => (),
        }
    }

    #[test]
    fn set_missing_goal_status() {
        let mut r = Roadmap::from_yaml(
            "
goal:
  depends:
  - finished
  - blocked

finished:
  status: finished

ready:
  depends:
  - finished

next:
  status: next

blocked:
  depends:
  - ready
  - next
",
        )
        .unwrap();
        r.set_missing_statuses();
        assert_eq!(r.get_step("goal").unwrap().status(), Status::Goal);
        assert_eq!(r.get_step("finished").unwrap().status(), Status::Finished);
        assert_eq!(r.get_step("ready").unwrap().status(), Status::Ready);
        assert_eq!(r.get_step("next").unwrap().status(), Status::Next);
        assert_eq!(r.get_step("blocked").unwrap().status(), Status::Blocked);
    }

    #[test]
    fn empty_dot() {
        let roadmap = Roadmap::new();
        assert_eq!(
            roadmap.as_dot(999).unwrap(),
            "digraph \"roadmap\" {
}
"
        );
    }

    #[test]
    fn simple_dot() {
        let mut roadmap = Roadmap::new();
        let mut first = Step::new("first", "");
        first.set_status(Status::Ready);
        let mut second = Step::new("second", "");
        second.add_dependency("first");
        second.set_status(Status::Goal);
        roadmap.add_step(&first).unwrap();
        roadmap.add_step(&second).unwrap();
        assert_eq!(
            roadmap.as_dot(999).unwrap(),
            "digraph \"roadmap\" {
first [label=\"\" style=filled fillcolor=\"#ffffff\" shape=\"ellipse\"];
second [label=\"\" style=filled fillcolor=\"#00eeee\" shape=\"diamond\"];
first -> second;
}
"
        );
    }

    #[test]
    fn from_empty_yaml() {
        let roadmap = Roadmap::from_yaml("{}");
        match roadmap {
            Ok(_) => panic!("expected error for empty dict"),
            _ => (),
        }
    }

    #[test]
    fn from_nonempty_yaml() {
        let roadmap = Roadmap::from_yaml(
            "
first:
  label: the first step
second:
  label: the second step
  depends:
  - first
",
        )
        .unwrap();

        let names = roadmap.step_names();
        assert_eq!(names.len(), 2);
        assert!(names.contains(&"first"));
        assert!(names.contains(&"second"));

        let first = roadmap.get_step("first").unwrap();
        assert_eq!(first.name(), "first");
        assert_eq!(first.label(), "the first step");
        let deps: Vec<&String> = first.dependencies().collect();
        assert_eq!(deps.len(), 0);

        let second = roadmap.get_step("second").unwrap();
        assert_eq!(second.name(), "second");
        assert_eq!(second.label(), "the second step");
        let deps: Vec<&String> = second.dependencies().collect();
        assert_eq!(deps, vec!["first"]);
    }
}