semifold-core 0.1.0

use camino::Utf8PathBuf;
use serde::Serialize;
use sha2::{Digest, Sha256};

use crate::{PackageId, VersionSourceId};

#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Serialize)]
pub struct SharedVersionEdit {
    pub source: VersionSourceId,
    pub packages: Vec<PackageId>,
}

/// Hash of the source content used while planning an edit.
#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
#[serde(transparent)]
pub struct FileHash(String);

impl FileHash {
    #[must_use]
    pub fn from_bytes(bytes: &[u8]) -> Self {
        Self(format!("{:x}", Sha256::digest(bytes)))
    }

    /// Restores a canonical SHA-256 value received across a serialized boundary.
    pub fn from_sha256(value: impl Into<String>) -> Result<Self, FileHashError> {
        let value = value.into();
        if value.len() == 64
            && value
                .bytes()
                .all(|byte| byte.is_ascii_digit() || (b'a'..=b'f').contains(&byte))
        {
            Ok(Self(value))
        } else {
            Err(FileHashError::InvalidSha256 { value })
        }
    }

    #[must_use]
    pub fn as_str(&self) -> &str {
        &self.0
    }
}

#[derive(Clone, Debug, Eq, PartialEq, thiserror::Error)]
pub enum FileHashError {
    #[error("file SHA-256 must contain exactly 64 lowercase hexadecimal characters: {value}")]
    InvalidSha256 { value: String },
}

/// Domain operation that produced a planned file edit.
#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd, Serialize)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum EditSource {
    PackageVersion {
        package: PackageId,
    },
    DependencyVersion {
        package: PackageId,
        dependency: PackageId,
    },
    WorkspaceDependencies {
        dependencies: Vec<PackageId>,
    },
    WorkspaceManifest {
        shared_versions: Vec<SharedVersionEdit>,
        dependencies: Vec<PackageId>,
    },
    Changelog {
        package: PackageId,
    },
}

/// Required target state when a planned edit is applied.
#[derive(Clone, Debug, Eq, PartialEq, Serialize)]
#[serde(tag = "kind", rename_all = "snake_case")]
pub enum FileEditExpectation {
    Existing { hash: FileHash },
    Missing,
}

/// A validated, not-yet-applied file content replacement.
#[derive(Clone, Debug, Eq, PartialEq, Serialize)]
pub struct FileEdit {
    pub path: Utf8PathBuf,
    pub expected: FileEditExpectation,
    pub new_content: String,
    pub source: EditSource,
}

#[cfg(test)]
mod tests {
    use super::{FileHash, FileHashError};

    #[test]
    fn hashes_source_bytes_with_sha256() {
        assert_eq!(
            FileHash::from_bytes(b"semifold").as_str(),
            "acfa94237c0f2abcae06590ebe6bb12455e24f07a9608a2418d618b540aee4e0"
        );
    }

    #[test]
    fn restores_only_canonical_sha256_values() {
        let value = "acfa94237c0f2abcae06590ebe6bb12455e24f07a9608a2418d618b540aee4e0";

        assert_eq!(FileHash::from_sha256(value).unwrap().as_str(), value);
        assert!(matches!(
            FileHash::from_sha256(value.to_uppercase()),
            Err(FileHashError::InvalidSha256 { .. })
        ));
        assert!(matches!(
            FileHash::from_sha256("short"),
            Err(FileHashError::InvalidSha256 { .. })
        ));
    }
}