fallow-api 3.27.0

//! Local-provider orchestration for advisory similar-code discovery.

use std::fmt::Write as _;
use std::path::{Path, PathBuf};
use std::time::{Duration, Instant};

use fallow_engine::source::similar_code::SimilarCodeSourceDigest;
use rustc_hash::FxHashMap;

mod cache;
mod protocol;
mod transport;

pub use protocol::SimilarCodeProviderStatus;

const EMBED_BATCH_SIZE: usize = 1;
const EMBED_RUN_TIMEOUT: Duration = Duration::from_mins(15);

/// Classified local-provider failure used by the programmatic runtime.
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) enum ProviderError {
    /// The exact companion or its pinned model is not installed yet.
    NotReady(String),
    /// An installed companion failed execution, provenance, or protocol checks.
    Failed(String),
}

impl ProviderError {
    pub(crate) fn message(&self) -> &str {
        match self {
            Self::NotReady(message) | Self::Failed(message) => message,
        }
    }
}

/// Opaque, validated handle obtained before project source is read.
pub(crate) struct ReadyProvider {
    path: PathBuf,
    pub(crate) status: SimilarCodeProviderStatus,
}

/// One transient source fragment selected for local embedding.
pub(crate) struct EmbeddingInput<'a> {
    pub(crate) source_sha256: SimilarCodeSourceDigest,
    pub(crate) source: &'a str,
}

/// Privacy-safe cache and provider accounting for one embedding pass.
pub(crate) struct EmbeddingResult {
    /// Vectors in input order. Missing entries represent a bounded partial pass.
    pub(crate) vectors: Vec<Option<Vec<f32>>>,
    pub(crate) cache_hits: usize,
    pub(crate) cache_misses: usize,
    pub(crate) cache_writes: usize,
    pub(crate) cache_invalid_entries: usize,
    pub(crate) cache_disabled: bool,
    pub(crate) cache_problem: Option<String>,
    pub(crate) provider_problem: Option<String>,
    pub(crate) inference_ms: f64,
    pub(crate) truncated_functions: usize,
}

/// Provider-neutral validated batch used by the private orchestration seam.
pub(crate) struct EmbeddingBatch {
    pub(crate) vectors: Vec<EmbeddingBatchVector>,
    pub(crate) inference_ms: f64,
    pub(crate) problem: Option<String>,
}

/// One validated vector returned by a private provider session.
pub(crate) struct EmbeddingBatchVector {
    pub(crate) key: u32,
    pub(crate) values: Vec<f32>,
    pub(crate) truncated: bool,
}

/// Private injectable session used by production transport and hermetic tests.
pub(crate) trait EmbeddingSession {
    fn embed(&mut self, functions: &[(u32, &str)]) -> Result<EmbeddingBatch, String>;
}

/// Private lazy session factory. The provider is not started on an all-cache-hit run.
pub(crate) trait EmbeddingSessionFactory {
    fn spawn(&mut self) -> Result<Box<dyn EmbeddingSession>, String>;
}

struct LocalEmbeddingSession {
    inner: transport::ProviderSession,
}

impl EmbeddingSession for LocalEmbeddingSession {
    fn embed(&mut self, functions: &[(u32, &str)]) -> Result<EmbeddingBatch, String> {
        let response = self.inner.embed(functions)?;
        let problem = (response.status != protocol::EmbedCompletionStatus::Complete)
            .then(|| transport::embed_problem(&response));
        Ok(EmbeddingBatch {
            vectors: response
                .vectors
                .into_iter()
                .map(|vector| EmbeddingBatchVector {
                    key: vector.key,
                    values: vector.values,
                    truncated: vector.truncated,
                })
                .collect(),
            inference_ms: response.timing.inference_ms,
            problem,
        })
    }
}

struct LocalEmbeddingSessionFactory<'a> {
    path: &'a Path,
}

impl EmbeddingSessionFactory for LocalEmbeddingSessionFactory<'_> {
    fn spawn(&mut self) -> Result<Box<dyn EmbeddingSession>, String> {
        transport::ProviderSession::spawn(self.path)
            .map(|inner| Box::new(LocalEmbeddingSession { inner }) as Box<dyn EmbeddingSession>)
    }
}

struct EmbeddingMiss {
    representative_index: usize,
    occurrence_indices: Vec<usize>,
}

struct EmbeddingPlan {
    vectors: Vec<Option<Vec<f32>>>,
    misses: Vec<EmbeddingMiss>,
    cache_hits: usize,
    cache_misses: usize,
    truncated_functions: usize,
}

/// Return the installed local provider status.
///
/// # Errors
///
/// Returns a structured message when the trusted sibling is missing, cannot be
/// executed, or reports incompatible provenance.
pub fn status() -> Result<SimilarCodeProviderStatus, String> {
    let sidecar = transport::discover_provider()?;
    let status = transport::provider_status(&sidecar)?;
    validate_status(&status)?;
    Ok(status)
}

/// Download and verify the pinned local model through the installed provider.
///
/// Callers must obtain explicit human confirmation before invoking this API.
/// MCP, NAPI, project configuration, and agent workflows intentionally do not
/// expose this mutation.
///
/// # Errors
///
/// Returns a structured message when setup fails or provenance is invalid.
pub fn setup_local() -> Result<SimilarCodeProviderStatus, String> {
    let sidecar = transport::discover_provider()?;
    let status = transport::setup_provider(&sidecar)?;
    validate_status(&status)?;
    if !status.model_ready {
        return Err("similar-code setup completed without a verified local model".to_owned());
    }
    Ok(status)
}

/// Immutable local provider identity used by public provenance output.
#[must_use]
pub fn provider_identity() -> (&'static str, &'static str, usize, &'static str) {
    (
        protocol::MODEL_ID,
        protocol::MODEL_REVISION,
        protocol::MODEL_DIMENSIONS,
        protocol::MODEL_LICENSE,
    )
}

/// Total bytes downloaded by an explicit local model setup.
#[must_use]
pub fn model_download_bytes() -> u64 {
    protocol::MODEL_ARTIFACTS
        .iter()
        .map(|artifact| artifact.size)
        .sum()
}

/// Resolve and validate the exact local companion before reading project source.
pub(crate) fn ready_provider() -> Result<ReadyProvider, ProviderError> {
    let path = transport::discover_provider().map_err(ProviderError::NotReady)?;
    let status = transport::provider_status(&path).map_err(ProviderError::Failed)?;
    validate_status(&status).map_err(ProviderError::Failed)?;
    if !status.model_ready {
        let problem = status.problem.unwrap_or_else(|| {
            "the pinned local model is not installed; run `fallow similar-code setup --local`"
                .to_owned()
        });
        return Err(ProviderError::NotReady(problem));
    }
    Ok(ReadyProvider { path, status })
}

/// Validate an exact companion path already resolved and signature-verified
/// by an official distribution adapter.
///
/// This exists for in-process hosts such as Node, whose process executable is
/// not the Fallow binary and therefore has no meaningful sibling discovery.
/// The path is never read from project config, PATH, or a model response.
pub(crate) fn ready_provider_from_adapter_path(
    path: &Path,
) -> Result<ReadyProvider, ProviderError> {
    if !path.is_file() {
        return Err(ProviderError::NotReady(format!(
            "verified similar-code companion is unavailable at {}",
            path.display()
        )));
    }
    let path = path.to_path_buf();
    let status = transport::provider_status(&path).map_err(ProviderError::Failed)?;
    validate_status(&status).map_err(ProviderError::Failed)?;
    if !status.model_ready {
        let problem = status.problem.unwrap_or_else(|| {
            "the pinned local model is not installed; run `fallow similar-code setup --local`"
                .to_owned()
        });
        return Err(ProviderError::NotReady(problem));
    }
    Ok(ReadyProvider { path, status })
}

/// Embed selected source fragments using the persistent source-digest cache.
pub(crate) fn embed_selected(
    provider: &ReadyProvider,
    project_root: &Path,
    no_cache: bool,
    inputs: &[EmbeddingInput<'_>],
) -> Result<EmbeddingResult, ProviderError> {
    let mut factory = LocalEmbeddingSessionFactory {
        path: &provider.path,
    };
    embed_selected_with_factory(
        Path::new(&provider.status.cache_dir),
        project_root,
        no_cache,
        inputs,
        EMBED_RUN_TIMEOUT,
        &mut factory,
    )
}

/// Private injectable embedding seam used by production transport and crate tests.
pub(crate) fn embed_selected_with_factory(
    provider_cache_dir: &Path,
    project_root: &Path,
    no_cache: bool,
    inputs: &[EmbeddingInput<'_>],
    run_timeout: Duration,
    factory: &mut dyn EmbeddingSessionFactory,
) -> Result<EmbeddingResult, ProviderError> {
    let mut cache = cache::VectorCache::load(provider_cache_dir, project_root, no_cache);
    let cache_invalid_entries = usize::from(cache.load_state == cache::CacheLoadState::Corrupt);
    let cache_disabled = cache.load_state == cache::CacheLoadState::Disabled;
    let mut plan = prepare_embedding_plan(&mut cache, inputs);
    let mut inference_ms = 0.0f64;
    let mut provider_problem = None;
    if !plan.misses.is_empty() {
        let started = Instant::now();
        let mut session = None;
        let mut batch_start = 0usize;
        while batch_start < plan.misses.len() {
            if started.elapsed() >= run_timeout {
                provider_problem =
                    Some("similar-code embedding stopped at the bounded run limit".to_owned());
                break;
            }
            let session = match session.as_mut() {
                Some(session) => session,
                None => session.insert(factory.spawn().map_err(ProviderError::Failed)?),
            };
            let batch_end = batch_start
                .saturating_add(EMBED_BATCH_SIZE)
                .min(plan.misses.len());
            let request = (batch_start..batch_end)
                .map(|group_index| {
                    let miss = &plan.misses[group_index];
                    let key = u32::try_from(group_index).map_err(|_| {
                        ProviderError::Failed(
                            "similar-code digest group exceeded protocol capacity".to_owned(),
                        )
                    })?;
                    Ok((key, inputs[miss.representative_index].source))
                })
                .collect::<Result<Vec<_>, ProviderError>>()?;
            match session.embed(&request) {
                Ok(batch) => {
                    validate_embedding_batch(&batch, &request).map_err(ProviderError::Failed)?;
                    inference_ms += batch.inference_ms;
                    if batch.problem.is_some() {
                        provider_problem = batch.problem;
                    }
                    for vector in batch.vectors {
                        let group_index = usize::try_from(vector.key).map_err(|_| {
                            ProviderError::Failed(
                                "similar-code provider returned an invalid digest-group key"
                                    .to_owned(),
                            )
                        })?;
                        apply_embedding_vector(
                            &mut cache,
                            inputs,
                            &mut plan,
                            group_index,
                            &vector.values,
                            vector.truncated,
                        )?;
                    }
                }
                Err(error) => {
                    provider_problem = Some(error);
                    break;
                }
            }
            batch_start = batch_end;
        }
    }
    let save = cache.save();

    Ok(EmbeddingResult {
        vectors: plan.vectors,
        cache_hits: plan.cache_hits,
        cache_misses: plan.cache_misses,
        cache_writes: save.durable_writes,
        cache_invalid_entries,
        cache_disabled,
        cache_problem: save.problem,
        provider_problem,
        inference_ms,
        truncated_functions: plan.truncated_functions,
    })
}

fn validate_embedding_batch(batch: &EmbeddingBatch, request: &[(u32, &str)]) -> Result<(), String> {
    if !batch.inference_ms.is_finite() || batch.inference_ms < 0.0 {
        return Err("similar-code provider returned invalid timing".to_owned());
    }
    let mut expected = request.iter().map(|(key, _)| *key).collect::<Vec<_>>();
    let mut actual = batch
        .vectors
        .iter()
        .map(|vector| vector.key)
        .collect::<Vec<_>>();
    expected.sort_unstable();
    actual.sort_unstable();
    if actual.windows(2).any(|pair| pair[0] == pair[1])
        || actual
            .iter()
            .any(|key| expected.binary_search(key).is_err())
        || batch.vectors.iter().any(|vector| {
            vector.values.len() != protocol::MODEL_DIMENSIONS
                || vector.values.iter().any(|value| !value.is_finite())
                || vector.values.iter().all(|value| *value == 0.0)
        })
        || (batch.vectors.len() == request.len()) == batch.problem.is_some()
    {
        return Err("similar-code provider returned an invalid embedding batch".to_owned());
    }
    Ok(())
}

fn prepare_embedding_plan(
    cache: &mut cache::VectorCache,
    inputs: &[EmbeddingInput<'_>],
) -> EmbeddingPlan {
    let mut vectors = vec![None; inputs.len()];
    let mut misses = Vec::<EmbeddingMiss>::new();
    let mut miss_groups: FxHashMap<SimilarCodeSourceDigest, usize> = FxHashMap::default();
    let mut cache_hits = 0usize;
    let mut cache_misses = 0usize;
    let mut truncated_functions = 0usize;
    for (index, input) in inputs.iter().enumerate() {
        if let Some(entry) = cache.get(&input.source_sha256) {
            vectors[index] = Some(entry.values.clone());
            cache_hits = cache_hits.saturating_add(1);
            truncated_functions =
                truncated_functions.saturating_add(usize::from(entry.token_truncated));
            continue;
        }

        cache_misses = cache_misses.saturating_add(1);
        if let Some(group_index) = miss_groups.get(&input.source_sha256).copied() {
            misses[group_index].occurrence_indices.push(index);
        } else {
            let group_index = misses.len();
            miss_groups.insert(input.source_sha256, group_index);
            misses.push(EmbeddingMiss {
                representative_index: index,
                occurrence_indices: vec![index],
            });
        }
    }
    EmbeddingPlan {
        vectors,
        misses,
        cache_hits,
        cache_misses,
        truncated_functions,
    }
}

fn apply_embedding_vector(
    cache: &mut cache::VectorCache,
    inputs: &[EmbeddingInput<'_>],
    plan: &mut EmbeddingPlan,
    group_index: usize,
    values: &[f32],
    token_truncated: bool,
) -> Result<(), ProviderError> {
    let miss = plan.misses.get(group_index).ok_or_else(|| {
        ProviderError::Failed(
            "similar-code provider returned an unknown digest-group key".to_owned(),
        )
    })?;
    let digest = inputs[miss.representative_index].source_sha256;
    cache.insert(digest, values.to_owned(), token_truncated);
    if token_truncated {
        plan.truncated_functions = plan
            .truncated_functions
            .saturating_add(miss.occurrence_indices.len());
    }
    for occurrence_index in &miss.occurrence_indices {
        plan.vectors[*occurrence_index] = Some(values.to_owned());
    }
    Ok(())
}

/// Remove the model-specific vector cache. Model artifacts remain installed.
fn clear_vector_cache(provider_cache_dir: &Path, project_root: &Path) -> Result<bool, String> {
    cache::clear(provider_cache_dir, project_root)
}

/// Remove only persisted similar-code vectors for one project.
///
/// The downloaded model is user-level state and is never removed here.
///
/// # Errors
///
/// Returns an error when config resolution or cache removal fails.
pub fn clear_project_cache(
    root: &Path,
    config_path: Option<&Path>,
    allow_remote_extends: bool,
) -> Result<bool, String> {
    let project = fallow_engine::project_config::config_for_project_with_load_options(
        root,
        config_path,
        fallow_config::ConfigLoadOptions {
            allow_remote_extends,
        },
    )
    .map_err(|error| format!("failed to load config: {error}"))?;
    let provider = status()?;
    clear_vector_cache(Path::new(&provider.cache_dir), &project.config.root)
}

pub(crate) fn model_artifact_sha256() -> &'static str {
    protocol::MODEL_ARTIFACTS
        .first()
        .map_or("", |artifact| artifact.sha256)
}

pub(crate) fn parameter_sha256() -> String {
    let digest = cache::parameter_digest();
    digest.iter().fold(
        String::with_capacity(digest.len().saturating_mul(2)),
        |mut output, byte| {
            let _ = write!(output, "{byte:02x}");
            output
        },
    )
}

pub(crate) const fn embedding_batch_size() -> usize {
    EMBED_BATCH_SIZE
}

pub(crate) const fn embedding_semantics_version() -> u32 {
    protocol::EMBEDDING_SEMANTICS_VERSION
}

fn validate_status(status: &SimilarCodeProviderStatus) -> Result<(), String> {
    if status.protocol_version != protocol::WIRE_PROTOCOL_VERSION
        || status.embedding_semantics_version != protocol::EMBEDDING_SEMANTICS_VERSION
        || status.sidecar_version != env!("CARGO_PKG_VERSION")
        || status.model_id != protocol::MODEL_ID
        || status.model_revision != protocol::MODEL_REVISION
        || status.dimensions != protocol::MODEL_DIMENSIONS
        || status.max_tokens != protocol::MODEL_MAX_TOKENS
        || status.license != protocol::MODEL_LICENSE
        || status.download_bytes != model_download_bytes()
        || !status.analysis_offline
        || (status.model_ready && !status.integrity_verified)
    {
        return Err(
            "similar-code companion provenance does not match this Fallow release".to_owned(),
        );
    }
    Ok(())
}

#[cfg(test)]
#[expect(
    clippy::unwrap_used,
    reason = "test fixture construction must fail immediately"
)]
mod tests {
    use super::*;

    #[test]
    fn duplicate_digest_is_inferred_once_and_warm_truncation_is_occurrence_aware() {
        let temp = tempfile::tempdir().unwrap();
        let cache_root = temp.path().join("user-cache");
        let provider_cache_dir = cache_root.join("models").join(protocol::MODEL_REVISION);
        let project_root = temp.path().join("project");
        std::fs::create_dir_all(&cache_root).unwrap();
        std::fs::create_dir_all(&project_root).unwrap();
        let digest = SimilarCodeSourceDigest::new([8; 32]);
        let inputs = [
            EmbeddingInput {
                source_sha256: digest,
                source: "function same() { return 1; }",
            },
            EmbeddingInput {
                source_sha256: digest,
                source: "function same() { return 1; }",
            },
        ];

        let mut cache = cache::VectorCache::load(&provider_cache_dir, &project_root, false);
        let mut cold = prepare_embedding_plan(&mut cache, &inputs);
        assert_eq!(cold.cache_misses, 2);
        assert_eq!(cold.misses.len(), 1);
        assert_eq!(cold.misses[0].occurrence_indices, vec![0, 1]);
        apply_embedding_vector(
            &mut cache,
            &inputs,
            &mut cold,
            0,
            &[0.25; protocol::MODEL_DIMENSIONS],
            true,
        )
        .unwrap();
        assert_eq!(cold.truncated_functions, 2);
        assert!(cold.vectors.iter().all(Option::is_some));
        assert_eq!(cache.save().durable_writes, 1);

        let mut cache = cache::VectorCache::load(&provider_cache_dir, &project_root, false);
        let warm = prepare_embedding_plan(&mut cache, &inputs);
        assert_eq!(warm.cache_hits, 2);
        assert_eq!(warm.cache_misses, 0);
        assert_eq!(warm.truncated_functions, 2);
        assert!(warm.misses.is_empty());
        assert!(warm.vectors.iter().all(Option::is_some));
    }
}