mod extractor;
mod hits;
mod resolver;

use crate::analyzer::common::{language_for_file, language_for_target};
use crate::analyzer::usages::csharp_graph::extractor::{ScanState, scan_file};
use crate::analyzer::usages::csharp_graph::resolver::{
    TargetKind, TargetSpec, resolve_csharp_analyzer,
};
use crate::analyzer::usages::model::{FuzzyResult, UsageHit};
use crate::analyzer::usages::outcome::{GraphFailureReason, GraphUsageOutcome};
use crate::analyzer::usages::traits::UsageAnalyzer;
use crate::analyzer::{CodeUnit, IAnalyzer, Language, ProjectFile};
use crate::hash::HashSet;
use std::collections::BTreeSet;

#[derive(Default)]
pub struct CSharpUsageGraphStrategy {
    _private: (),
}

impl CSharpUsageGraphStrategy {
    pub fn new() -> Self {
        Self { _private: () }
    }

    pub fn can_handle(target: &CodeUnit) -> bool {
        language_for_target(target) == Language::CSharp
    }

    pub(crate) fn find_graph_usages(
        &self,
        analyzer: &dyn IAnalyzer,
        overloads: &[CodeUnit],
        candidate_files: &HashSet<ProjectFile>,
        max_usages: usize,
    ) -> GraphUsageOutcome {
        if overloads.is_empty() {
            return GraphUsageOutcome::Resolved(FuzzyResult::empty_success());
        }

        let target = &overloads[0];
        if language_for_target(target) != Language::CSharp {
            return GraphUsageOutcome::fallback_safe(
                target.fq_name(),
                GraphFailureReason::UnsupportedTargetLanguage("target is not C#"),
                "CSharpUsageGraphStrategy",
            );
        }

        let Some(csharp) = resolve_csharp_analyzer(analyzer) else {
            return GraphUsageOutcome::fallback_safe(
                target.fq_name(),
                GraphFailureReason::MissingAnalyzerCapability(
                    "analyzer does not expose CSharpAnalyzer",
                ),
                "CSharpUsageGraphStrategy",
            );
        };

        let Some(spec) = TargetSpec::from_target(analyzer, target) else {
            return GraphUsageOutcome::fallback_safe(
                target.fq_name(),
                GraphFailureReason::UnsupportedTargetShape("target shape is unsupported"),
                "CSharpUsageGraphStrategy",
            );
        };

        let files: HashSet<ProjectFile> = candidate_files
            .iter()
            .filter(|file| language_for_file(file) == Language::CSharp)
            .cloned()
            .chain(std::iter::once(target.source().clone()))
            .collect();

        let mut hits: BTreeSet<UsageHit> = BTreeSet::new();
        let mut saw_unproven_match = false;
        let mut limit_exceeded = false;
        let mut state = ScanState {
            max_usages,
            hits: &mut hits,
            saw_unproven_match: &mut saw_unproven_match,
            limit_exceeded: &mut limit_exceeded,
        };
        for file in files {
            scan_file(csharp, analyzer, &file, &spec, &mut state);
            if *state.limit_exceeded {
                break;
            }
        }

        if saw_unproven_match && spec.kind != TargetKind::Type {
            return GraphUsageOutcome::fallback_safe(
                target.fq_name(),
                GraphFailureReason::UnsafeInference("no proven structured hits"),
                "CSharpUsageGraphStrategy",
            );
        }

        if limit_exceeded || hits.len() > max_usages {
            return GraphUsageOutcome::Resolved(FuzzyResult::TooManyCallsites {
                short_name: target.short_name().to_string(),
                total_callsites: hits.len(),
                limit: max_usages,
            });
        }

        GraphUsageOutcome::Resolved(FuzzyResult::success(target.clone(), hits))
    }
}

impl UsageAnalyzer for CSharpUsageGraphStrategy {
    fn find_usages(
        &self,
        analyzer: &dyn IAnalyzer,
        overloads: &[CodeUnit],
        candidate_files: &HashSet<ProjectFile>,
        max_usages: usize,
    ) -> FuzzyResult {
        self.find_graph_usages(analyzer, overloads, candidate_files, max_usages)
            .into_fuzzy_result()
    }
}
