//! [`cmdtree`] tree and action completions.
//!
//! `TreeCompleter` is an out-of-the-box working completer of classes and actions for an existing
//! [`Commander`].
//!
//! [`cmdtree`]: cmdtree
//! [`Commander`]: cmdtree::Commander

use super::*;
use cmdtree::completion::CompletionInfo;
use cmdtree::Commander;
use std::borrow::Cow;

/// Completion items for the [`cmdtree`] class and action structure.
///
/// # Example
/// ```rust
/// use papyrus::cmdtree::*;
///
/// let cmdr = Builder::default_config("example-completion")
///             .begin_class("class-one", "class help message")
///                 .add_action("one", "first action", |_, _| ())
///                 .add_action("two", "second action", |_, _| ())
///             .end_class()
///             .into_commander()
///             .unwrap();
///
/// let cmpltr = papyrus::complete::cmdr::TreeCompleter::build(&cmdr);
///
/// // prefixed with the command ':' character. (papyrus specific)
/// let mut matches = cmpltr.complete(":cla");
///
/// let nmatch = matches.next().unwrap();
/// assert_eq!(nmatch.0, ":class-one");
/// assert_eq!(nmatch.1.completestr, ":class-one");
/// assert_eq!(nmatch.1.itemtype, ItemType::Class);
/// assert_eq!(nmatch.1.help_msg.as_str(), "class help message");
///
/// let nmatch = matches.next().unwrap();
/// assert_eq!(nmatch.0, ":class-one one");
/// assert_eq!(nmatch.1.completestr, ":class-one one");
/// assert_eq!(nmatch.1.itemtype, ItemType::Action);
/// assert_eq!(nmatch.1.help_msg.as_str(), "first action");
///
/// let nmatch = matches.next().unwrap();
/// assert_eq!(nmatch.0, ":class-one two");
/// assert_eq!(nmatch.1.completestr, ":class-one two");
/// assert_eq!(nmatch.1.itemtype, ItemType::Action);
/// assert_eq!(nmatch.1.help_msg.as_str(), "second action");
///
/// assert_eq!(matches.next(), None);
/// ```
///
/// [`cmdtree`]: cmdtree
pub struct TreeCompleter {
    items: Vec<CompletionInfo>,
}

impl TreeCompleter {
    /// Build the `TreeCompleter` from the current state of the `Commander`.
    pub fn build<T>(cmdr: &Commander<T>) -> Self {
        let mut items = cmdtree::completion::create_tree_completion_items(&cmdr);

        items.iter_mut().for_each(|x| {
            if cmdr.at_root() {
                x.completestr.insert_str(0, crate::CMD_PREFIX);
            }
        });

        Self { items }
    }

    /// Returns the start position of the _last_ word which is broken in context to cmdtree.
    pub fn word_break(line: &str) -> usize {
        word_break_start(line, &[' '])
    }

    /// Get the completions of the tree structure if it matches the line.
    ///
    /// The first element is the completed string, starting from the `word_break` position.
    pub fn complete<'b>(
        &'b self,
        line: &'b str,
    ) -> impl Iterator<Item = (&'b str, &'b CompletionInfo)> {
        cmdtree::completion::tree_completions(line, self.items.iter())
    }
}

/// Matching of [`cmdtree`] actions.
///
/// [`cmdtree`]: cmdtree
pub struct ActionArgComplete {
    /// All actions available in current state.
    pub items: Vec<cmdtree::completion::ActionMatch>,
}

impl ActionArgComplete {
    /// Build the `ActionArgComplete` with the given `Commander` state.
    pub fn build<T>(cmdr: &Commander<T>) -> Self {
        let mut items = cmdtree::completion::create_action_completion_items(&cmdr);

        items.iter_mut().for_each(|x| {
            if cmdr.at_root() {
                x.info.completestr.insert_str(0, crate::CMD_PREFIX);
            }
        });

        Self { items }
    }

    /// Determine if the current line matches any available actions. Checks that
    /// the qualified path is within `valid`. Returns the argument scope completion
    /// inputs, such as line, word.
    pub fn find<'a>(&self, line: &'a str, valid: &[&str]) -> Option<ArgComplete<'a>> {
        self.items
            .iter()
            .find(|x| line.starts_with(x.info.completestr.as_str()))
            .and_then(|x| {
                if valid.contains(&x.qualified_path.as_str()) {
                    let line = &line[x.info.completestr.len()..];
                    let word_start = word_break_start(line, &[' ']);
                    Some(ArgComplete {
                        line,
                        word: &line[word_start..],
                        word_start,
                        help_msg: x.info.help_msg.inner_cow.clone(),
                    })
                } else {
                    None
                }
            })
    }
}

/// The argument scoped inputs for completing.
///
/// The information here is scoped to the argument slice of a line, ie
/// if the line was `some action arg1 arg2` then the `line` would be "arg1 arg2", the
/// `word` would be "arg2" (and if say it was partial it would only return the partial part), and
/// the `word_start` would be 5.
#[derive(Debug, PartialEq)]
pub struct ArgComplete<'a> {
    /// The complete line, scoped to argument section.
    pub line: &'a str,
    /// The final word, broken on spaces.
    pub word: &'a str,
    /// The start index inside `line` of `word`.
    pub word_start: usize,
    /// The help message of the command action.
    pub help_msg: Cow<'static, str>,
}

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

    #[test]
    fn arg_complete_test() {
        let items = vec![cmdtree::completion::ActionMatch {
            info: CompletionInfo {
                completestr: "some action ".to_string(),
                itemtype: cmdtree::ItemType::Action,
                help_msg: "".into(),
            },
            qualified_path: "some..action".to_string(),
        }];

        let valid = ["some..action"];

        let a = ActionArgComplete { items };

        let f = a.find("some action arg1", &valid).unwrap();

        assert_eq!(
            f,
            ArgComplete {
                line: "arg1",
                word: "arg1",
                word_start: 0,
                help_msg: Cow::Borrowed("")
            }
        );

        let f = a.find("some action arg1 argu", &valid).unwrap();

        assert_eq!(
            f,
            ArgComplete {
                line: "arg1 argu",
                word: "argu",
                word_start: 5,
                help_msg: Cow::Borrowed("")
            }
        );
    }
}