// file: crates/ksp-config-lib/src/registry.rs
// version: 1

/// Bootstrap argument used to replace a known Config filename mapping.
pub const ARG_FILE_MAP: &str = "--filemap";
/// Logical file identifier for the standard Logging configuration document.
pub const FILE_ID_STD_LOGGING: &str = "cfg.std.logging";
/// Logical file identifier for the standard Logging JSON Schema document.
pub const FILE_ID_SCHEMA_STD_LOGGING: &str = "schema.std.logging";
/// Default physical filename for the standard Logging configuration document.
pub const DEFAULT_STD_LOGGING_FILENAME: &str = "std.logging.json";
/// Default physical filename for the standard Logging JSON Schema document.
pub const DEFAULT_STD_LOGGING_SCHEMA_FILENAME: &str = "std.logging.schema.json";

/// Stable logical identifier for a Config-managed file.
#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub struct ConfigFileId(String);

impl ConfigFileId {
    /// Creates and validates a logical Config file identifier.
    pub fn new(value: impl std::convert::Into<String>) -> ksp_core_lib::Result<Self> {
        let value = value.into();
        let validated = validate_file_id(value.as_str());
        return match validated {
            std::result::Result::Ok(()) => std::result::Result::Ok(Self(value)),
            std::result::Result::Err(error) => std::result::Result::Err(error),
        };
    }

    /// Returns the logical identifier as text.
    #[must_use]
    pub fn as_str(&self) -> &str {
        return self.0.as_str();
    }
}

/// Physical root category used to resolve a Config-managed file.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ConfigFileKind {
    /// Runtime configuration document resolved below `cfgpath`.
    Config,
    /// JSON Schema document resolved below `schemapath`.
    Schema,
}

/// Logical descriptor associating a stable file identifier with its physical filename and root category.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ConfigFileDescriptor {
    file_id: ConfigFileId,
    kind: ConfigFileKind,
    filename: std::path::PathBuf,
}

impl ConfigFileDescriptor {
    /// Returns the stable logical identifier.
    #[must_use]
    pub fn file_id(&self) -> &ConfigFileId {
        return &self.file_id;
    }

    /// Returns the root category used when resolving the file.
    #[must_use]
    pub fn kind(&self) -> ConfigFileKind {
        return self.kind;
    }

    /// Returns the relative physical filename currently mapped to the identifier.
    #[must_use]
    pub fn filename(&self) -> &std::path::Path {
        return self.filename.as_path();
    }

    fn new(file_id: &'static str, kind: ConfigFileKind, filename: &'static str) -> ksp_core_lib::Result<Self> {
        let file_id = ConfigFileId::new(file_id);
        let file_id = match file_id {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        let kind_validation = validate_kind_prefix(&file_id, kind);
        match kind_validation {
            std::result::Result::Ok(()) => {},
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        }
        let filename = validate_relative_filename(&file_id, std::path::PathBuf::from(filename));
        return match filename {
            std::result::Result::Ok(value) => std::result::Result::Ok(Self { file_id, kind, filename: value }),
            std::result::Result::Err(error) => std::result::Result::Err(error),
        };
    }
}

/// Registry of KSP-known logical Config files and their replaceable physical filenames.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ConfigFileRegistry {
    descriptors: std::collections::BTreeMap<ConfigFileId, ConfigFileDescriptor>,
}

impl ConfigFileRegistry {
    /// Creates the registry containing the KSP default file mappings known in the current release.
    pub fn defaults() -> ksp_core_lib::Result<Self> {
        let logging = ConfigFileDescriptor::new(FILE_ID_STD_LOGGING, ConfigFileKind::Config, DEFAULT_STD_LOGGING_FILENAME);
        let logging = match logging {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        let logging_schema = ConfigFileDescriptor::new(FILE_ID_SCHEMA_STD_LOGGING, ConfigFileKind::Schema, DEFAULT_STD_LOGGING_SCHEMA_FILENAME);
        let logging_schema = match logging_schema {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        return build_registry([logging, logging_schema]);
    }

    /// Creates the default registry and applies repeatable `--filemap=<file_id>=<filename>` overrides from raw process arguments.
    ///
    /// Unrelated arguments are ignored. A repeated mapping for the same known `file_id` is accepted and the last mapping wins.
    pub fn from_args(args: &[std::ffi::OsString]) -> ksp_core_lib::Result<Self> {
        let registry = Self::defaults();
        let mut registry = match registry {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        let mut index: usize = 0;
        while index < args.len() {
            let application = apply_file_map_argument(&mut registry, &args[index]);
            match application {
                std::result::Result::Ok(()) => {},
                std::result::Result::Err(error) => return std::result::Result::Err(error),
            }
            index += 1;
        }
        return std::result::Result::Ok(registry);
    }

    /// Returns the descriptor associated with a known logical file identifier.
    pub fn descriptor(&self, file_id: &ConfigFileId) -> ksp_core_lib::Result<&ConfigFileDescriptor> {
        return match self.descriptors.get(file_id) {
            std::option::Option::Some(descriptor) => std::result::Result::Ok(descriptor),
            std::option::Option::None => std::result::Result::Err(unknown_file_id_error(file_id.as_str())),
        };
    }

    /// Resolves a known logical file identifier below the bootstrap root selected by its descriptor kind.
    pub fn resolve_path(&self, bootstrap: &crate::ConfigBootstrapOptions, file_id: &ConfigFileId) -> ksp_core_lib::Result<std::path::PathBuf> {
        let descriptor = self.descriptor(file_id);
        let descriptor = match descriptor {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        let root = match descriptor.kind() {
            ConfigFileKind::Config => bootstrap.cfg_path(),
            ConfigFileKind::Schema => bootstrap.schema_path(),
        };
        return std::result::Result::Ok(root.join(descriptor.filename()));
    }

    /// Replaces the physical filename of one known logical identifier while preserving its kind and logical identity.
    pub fn with_filename_override(mut self, file_id: &ConfigFileId, filename: impl std::convert::Into<std::path::PathBuf>) -> ksp_core_lib::Result<Self> {
        let update = self.set_filename_override(file_id, filename.into());
        return match update {
            std::result::Result::Ok(()) => std::result::Result::Ok(self),
            std::result::Result::Err(error) => std::result::Result::Err(error),
        };
    }

    fn set_filename_override(&mut self, file_id: &ConfigFileId, filename: std::path::PathBuf) -> ksp_core_lib::Result<()> {
        let descriptor = self.descriptors.get(file_id);
        let descriptor = match descriptor {
            std::option::Option::Some(value) => value.clone(),
            std::option::Option::None => return std::result::Result::Err(unknown_file_id_error(file_id.as_str())),
        };
        let filename = validate_relative_filename(file_id, filename);
        let filename = match filename {
            std::result::Result::Ok(value) => value,
            std::result::Result::Err(error) => return std::result::Result::Err(error),
        };
        let updated = ConfigFileDescriptor { file_id: descriptor.file_id.clone(), kind: descriptor.kind, filename };
        self.descriptors.insert(file_id.clone(), updated);
        return std::result::Result::Ok(());
    }
}

fn build_registry<const N: usize>(descriptors: [ConfigFileDescriptor; N]) -> ksp_core_lib::Result<ConfigFileRegistry> {
    let mut registry = ConfigFileRegistry { descriptors: std::collections::BTreeMap::new() };
    for descriptor in descriptors {
        let file_id = descriptor.file_id.clone();
        let duplicate_id = file_id.clone();
        let previous = registry.descriptors.insert(file_id, descriptor);
        if previous.is_some() {
            return std::result::Result::Err(duplicate_file_id_error(duplicate_id.as_str()));
        }
    }
    return std::result::Result::Ok(registry);
}

fn apply_file_map_argument(registry: &mut ConfigFileRegistry, argument: &std::ffi::OsStr) -> ksp_core_lib::Result<()> {
    let text = match argument.to_str() {
        std::option::Option::Some(value) => value,
        std::option::Option::None => return std::result::Result::Ok(()),
    };
    if text == ARG_FILE_MAP {
        return std::result::Result::Err(invalid_file_mapping_error("--filemap requires the inline form --filemap=<file_id>=<filename>"));
    }
    let prefix = "--filemap=";
    let mapping = match text.strip_prefix(prefix) {
        std::option::Option::Some(value) => value,
        std::option::Option::None => return std::result::Result::Ok(()),
    };
    let separator = mapping.find('=');
    let separator = match separator {
        std::option::Option::Some(value) => value,
        std::option::Option::None => {
            return std::result::Result::Err(invalid_file_mapping_error("file mapping must contain a file_id and filename separated by '='"));
        },
    };
    let file_id_text = &mapping[..separator];
    let filename_text = &mapping[separator + 1..];
    if file_id_text.is_empty() || filename_text.is_empty() {
        return std::result::Result::Err(invalid_file_mapping_error("file mapping requires non-empty file_id and filename values"));
    }
    let file_id = ConfigFileId::new(file_id_text);
    let file_id = match file_id {
        std::result::Result::Ok(value) => value,
        std::result::Result::Err(error) => return std::result::Result::Err(error),
    };
    return registry.set_filename_override(&file_id, std::path::PathBuf::from(filename_text));
}

fn validate_file_id(value: &str) -> ksp_core_lib::Result<()> {
    if value.is_empty() || value.starts_with('.') || value.ends_with('.') || value.contains("..") {
        return std::result::Result::Err(invalid_file_id_error(value));
    }
    let mut valid = true;
    for byte in value.bytes() {
        let allowed = byte.is_ascii_lowercase() || byte.is_ascii_digit() || byte == b'.' || byte == b'_' || byte == b'-';
        if !allowed {
            valid = false;
        }
    }
    if !valid {
        return std::result::Result::Err(invalid_file_id_error(value));
    }
    return std::result::Result::Ok(());
}

fn validate_kind_prefix(file_id: &ConfigFileId, kind: ConfigFileKind) -> ksp_core_lib::Result<()> {
    let valid = match kind {
        ConfigFileKind::Config => file_id.as_str().starts_with("cfg."),
        ConfigFileKind::Schema => file_id.as_str().starts_with("schema."),
    };
    if !valid {
        return std::result::Result::Err(invalid_file_mapping_with_id_error(file_id.as_str(), "file_id prefix does not match descriptor kind"));
    }
    return std::result::Result::Ok(());
}

fn validate_relative_filename(file_id: &ConfigFileId, filename: std::path::PathBuf) -> ksp_core_lib::Result<std::path::PathBuf> {
    if filename.as_os_str().is_empty() || filename.is_absolute() {
        return std::result::Result::Err(invalid_filename_error(file_id.as_str(), &filename));
    }
    let mut has_normal_component = false;
    for component in filename.components() {
        match component {
            std::path::Component::Normal(_) => has_normal_component = true,
            std::path::Component::CurDir | std::path::Component::ParentDir | std::path::Component::RootDir | std::path::Component::Prefix(_) => {
                return std::result::Result::Err(invalid_filename_error(file_id.as_str(), &filename));
            },
        }
    }
    if !has_normal_component {
        return std::result::Result::Err(invalid_filename_error(file_id.as_str(), &filename));
    }
    return std::result::Result::Ok(filename);
}

fn invalid_file_id_error(file_id: &str) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_ID_INVALID, "Config file_id is invalid")
        .with_context("file_id", file_id)
        .with_context("reason", "expected lowercase ASCII segments separated by single dots");
}

fn unknown_file_id_error(file_id: &str) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_ID_UNKNOWN, "Config file_id is not registered").with_context("file_id", file_id);
}

fn duplicate_file_id_error(file_id: &str) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_ID_DUPLICATE, "Config file_id is registered more than once").with_context("file_id", file_id);
}

fn invalid_file_mapping_error(reason: &'static str) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_MAPPING_INVALID, "Config file mapping is invalid").with_context("reason", reason);
}

fn invalid_file_mapping_with_id_error(file_id: &str, reason: &'static str) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_MAPPING_INVALID, "Config file mapping is invalid")
        .with_context("file_id", file_id)
        .with_context("reason", reason);
}

fn invalid_filename_error(file_id: &str, filename: &std::path::Path) -> ksp_core_lib::Error {
    return ksp_core_lib::Error::new(crate::ERROR_CODE_FILE_MAPPING_INVALID, "Config mapped filename is invalid")
        .with_context("file_id", file_id)
        .with_context("filename", filename.to_string_lossy().into_owned())
        .with_context("reason", "filename must stay relative to its Config-owned root without traversal components");
}

#[cfg(test)]
#[path = "../unit_tests/registry.rs"]
mod tests;