use crate::*;

use std::collections::HashSet;


pub struct MergeError<'a> {
    pub resolver: &'a Resolver,
    /// A list of source units involved in a cycle.
    pub cyclic_unit_ids: Vec<usize>,
}

impl MergeError<'_> {
    pub fn report(&self) {
        let message = "A cyclic dependency was found between the following files:";
        let mut details = InkedString::new();
        for id in &self.cyclic_unit_ids {
            let unit = &self.resolver.source_units[*id];
            let path = &unit.source_unit.path();
            match unit.source_unit.name() {
                Some(name) => {
                    details.push(ink!("{name}"));
                    details.push(ink!(" ({path})\n").dim());
                }
                None => {
                    details.push(ink!("{path}\n"));
                }
            };
            // Print each parent involved in the dependency cycle.
            for parent_id in &unit.parent_ids {
                if !self.cyclic_unit_ids.contains(parent_id) { continue; }
                let parent_unit = &self.resolver.source_units[*parent_id];
                let parent_path = &parent_unit.source_unit.path();
                match parent_unit.source_unit.name() {
                    Some(parent_name) => {
                        details.push(ink!("  => {parent_name}"));
                        details.push(ink!(" ({parent_path})\n").dim());
                    }
                    None => {
                        details.push(ink!("  => {parent_path}\n"));
                    }
                };
                // Report all referenced symbols that are defined by this parent.
                let mut reported_definition_ids = HashSet::new();
                for reference in &self.resolver.resolved {
                    if reference.tracked.source_id == *id {
                        if reported_definition_ids.insert(reference.definition) {
                            let definition = &self.resolver.definitions[reference.definition];
                            if definition.tracked.source_id == *parent_id {
                                details.push(ink!("       {:?}\n", definition.tracked.symbol));
                            }
                        }
                    }
                }
            }
        }
        log_error(message, Some(details));
    }
}