cfgmatic_source/application/

loader.rs

//! Loader service for loading configuration from sources.
//!
//! This module provides the [`Loader`] service which is responsible for
//! loading configuration from various sources and parsing it.
//!
//! # Example
//!
//! ```rust,ignore
//! use cfgmatic_source::application::Loader;
//! use cfgmatic_source::infrastructure::FileSource;
//!
//! let loader = Loader::builder()
//!     .fail_fast(false)
//!     .build();
//!
//! let content = loader.load_from_source(&source)?;
//! let config: MyConfig = loader.parse_content(content)?;
//! ```

use serde::de::DeserializeOwned;

use crate::config::{LoadOptions, MergeStrategy};
use crate::domain::{Format, ParsedContent, RawContent, Result, Source, SourceError};

/// Service for loading configuration from sources.
///
/// The Loader is responsible for:
/// - Loading raw content from sources
/// - Detecting and parsing formats
/// - Converting to typed configuration
#[derive(Debug, Clone)]
pub struct Loader {
    /// Loading options.
    options: LoadOptions,

    /// Default format to use when detection fails.
    default_format: Option<Format>,
}

impl Loader {
    /// Create a new Loader with default options.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Create a builder for constructing a Loader.
    #[must_use]
    pub fn builder() -> LoaderBuilder {
        LoaderBuilder::new()
    }

    /// Get the load options.
    #[must_use]
    pub fn options(&self) -> &LoadOptions {
        &self.options
    }

    /// Load raw content from a source.
    ///
    /// # Errors
    ///
    /// Returns an error if the source cannot be read.
    pub fn load_raw<S: Source>(&self, source: &S) -> Result<RawContent> {
        source.validate()?;
        source.load_raw()
    }

    /// Load and parse content from a source.
    ///
    /// # Errors
    ///
    /// Returns an error if loading or parsing fails.
    pub fn load<S: Source>(&self, source: &S) -> Result<ParsedContent> {
        let raw = self.load_raw(source)?;
        self.parse_raw(raw, source.detect_format())
    }

    /// Load and parse content from a source into a specific type.
    ///
    /// # Errors
    ///
    /// Returns an error if loading, parsing, or deserialization fails.
    pub fn load_as<S: Source, T: DeserializeOwned>(&self, source: &S) -> Result<T> {
        let raw = self.load_raw(source)?;
        // Treat Unknown as None to allow fallback to default_format
        let format = source
            .detect_format()
            .and_then(|f| if f == Format::Unknown { None } else { Some(f) })
            .or(self.default_format);

        match format {
            Some(fmt) => fmt.parse_as(raw.as_str()?.as_ref()),
            None => Err(SourceError::unsupported("cannot detect format")),
        }
    }

    /// Parse raw content using a specific format.
    ///
    /// # Errors
    ///
    /// Returns an error if parsing fails.
    pub fn parse(&self, raw: &RawContent, format: Format) -> Result<ParsedContent> {
        let content = raw.as_str()?;
        format.parse(content.as_ref())
    }

    /// Parse raw content, detecting the format.
    ///
    /// # Errors
    ///
    /// Returns an error if parsing fails or format cannot be detected.
    pub fn parse_raw(
        &self,
        raw: RawContent,
        detected_format: Option<Format>,
    ) -> Result<ParsedContent> {
        // Treat Unknown as None to allow fallback to default_format
        let format = detected_format
            .and_then(|f| if f == Format::Unknown { None } else { Some(f) })
            .or(self.default_format);

        match format {
            Some(fmt) => self.parse(&raw, fmt),
            None => {
                // Try to detect from content
                let content = raw.as_str()?;
                if let Some(fmt) = Format::from_content(content.as_ref()) {
                    return fmt.parse(content.as_ref());
                }
                Err(SourceError::unsupported("cannot detect format"))
            }
        }
    }

    /// Merge multiple parsed contents.
    ///
    /// Uses the merge strategy from options.
    #[must_use]
    pub fn merge(&self, contents: Vec<ParsedContent>) -> ParsedContent {
        if contents.is_empty() {
            return ParsedContent::Null;
        }

        let strategy = self.options.merge_strategy;

        contents
            .into_iter()
            .reduce(|acc, content| match strategy {
                MergeStrategy::Replace => content,
                MergeStrategy::Deep | MergeStrategy::Shallow | MergeStrategy::Strict => {
                    acc.merge(&content)
                }
            })
            .unwrap_or(ParsedContent::Null)
    }

    /// Convert parsed content to a specific type.
    ///
    /// # Errors
    ///
    /// Returns an error if deserialization fails.
    pub fn to_type<T: DeserializeOwned>(&self, content: ParsedContent) -> Result<T> {
        content.to_type()
    }

    /// Load from multiple sources and merge.
    ///
    /// Sources are loaded in order and merged according to the merge strategy.
    /// Optional sources that fail are skipped if `ignore_optional_missing` is true.
    ///
    /// # Errors
    ///
    /// Returns an error if a required source fails and `fail_fast` is true.
    pub fn load_multiple<S: Source>(&self, sources: &[S]) -> Result<ParsedContent> {
        let mut contents = Vec::new();
        let mut errors: Vec<(String, SourceError)> = Vec::new();

        for source in sources {
            match self.load(source) {
                Ok(content) => contents.push(content),
                Err(e) => {
                    if source.is_optional() && self.options.ignore_optional_missing {
                        continue;
                    }
                    if self.options.fail_fast {
                        return Err(e);
                    }
                    errors.push((source.display_name(), e));
                }
            }
        }

        if !errors.is_empty() && contents.is_empty() {
            let error_messages: Vec<String> = errors
                .into_iter()
                .map(|(name, e)| format!("{}: {}", name, e))
                .collect();
            return Err(SourceError::custom(&error_messages.join(", ")));
        }

        Ok(self.merge(contents))
    }
}

impl Default for Loader {
    fn default() -> Self {
        Self {
            options: LoadOptions::default(),
            default_format: None,
        }
    }
}

/// Builder for [`Loader`].
#[derive(Debug, Clone, Default)]
pub struct LoaderBuilder {
    options: Option<LoadOptions>,
    default_format: Option<Format>,
}

impl LoaderBuilder {
    /// Create a new builder.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Set the load options.
    #[must_use]
    pub fn options(mut self, options: LoadOptions) -> Self {
        self.options = Some(options);
        self
    }

    /// Set the merge strategy.
    #[must_use]
    pub fn merge_strategy(mut self, strategy: MergeStrategy) -> Self {
        let mut options = self.options.unwrap_or_default();
        options.merge_strategy = strategy;
        self.options = Some(options);
        self
    }

    /// Set whether to fail fast on errors.
    #[must_use]
    pub fn fail_fast(mut self, fail_fast: bool) -> Self {
        let mut options = self.options.unwrap_or_default();
        options.fail_fast = fail_fast;
        self.options = Some(options);
        self
    }

    /// Set the default format when detection fails.
    #[must_use]
    pub fn default_format(mut self, format: Format) -> Self {
        self.default_format = Some(format);
        self
    }

    /// Build the Loader.
    #[must_use]
    pub fn build(self) -> Loader {
        Loader {
            options: self.options.unwrap_or_default(),
            default_format: self.default_format,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::domain::{SourceKind, SourceMetadata};
    use std::collections::BTreeMap;

    /// Test source implementation.
    struct TestSource {
        content: String,
        format: Format,
        optional: bool,
    }

    impl TestSource {
        fn new(content: &str, format: Format) -> Self {
            Self {
                content: content.to_string(),
                format,
                optional: false,
            }
        }

        fn with_optional(mut self, optional: bool) -> Self {
            self.optional = optional;
            self
        }
    }

    impl Source for TestSource {
        fn kind(&self) -> SourceKind {
            SourceKind::Memory
        }

        fn metadata(&self) -> SourceMetadata {
            SourceMetadata::new("test")
        }

        fn load_raw(&self) -> Result<RawContent> {
            Ok(RawContent::from_string(&self.content))
        }

        fn detect_format(&self) -> Option<Format> {
            Some(self.format)
        }

        fn is_optional(&self) -> bool {
            self.optional
        }
    }

    #[test]
    fn test_loader_new() {
        let loader = Loader::new();
        assert_eq!(loader.options().merge_strategy, MergeStrategy::Deep);
    }

    #[test]
    fn test_loader_builder() {
        let loader = Loader::builder()
            .merge_strategy(MergeStrategy::Replace)
            .fail_fast(false)
            .build();

        assert_eq!(loader.options().merge_strategy, MergeStrategy::Replace);
        assert!(!loader.options().fail_fast);
    }

    #[test]
    fn test_loader_load_raw() {
        let source = TestSource::new(r#"key = "value""#, Format::Toml);
        let loader = Loader::new();

        let raw = loader.load_raw(&source).unwrap();
        assert!(!raw.is_empty());
    }

    #[test]
    fn test_loader_load() {
        let source = TestSource::new(r#"key = "value""#, Format::Toml);
        let loader = Loader::new();

        let content = loader.load(&source).unwrap();
        assert!(content.is_object());
    }

    #[test]
    fn test_loader_parse() {
        let raw = RawContent::from_string(r#"{"key": "value"}"#);
        let loader = Loader::new();

        let content = loader.parse(&raw, Format::Json).unwrap();
        assert!(content.is_object());
    }

    #[test]
    fn test_loader_merge_empty() {
        let loader = Loader::new();
        let result = loader.merge(vec![]);
        assert!(result.is_null());
    }

    #[test]
    fn test_loader_merge_single() {
        let loader = Loader::new();
        let mut obj = BTreeMap::new();
        obj.insert(
            "key".to_string(),
            ParsedContent::String("value".to_string()),
        );
        let content = ParsedContent::Object(obj);

        let result = loader.merge(vec![content.clone()]);
        assert_eq!(result, content);
    }

    #[test]
    fn test_loader_merge_multiple() {
        let loader = Loader::builder()
            .merge_strategy(MergeStrategy::Deep)
            .build();

        let mut obj1 = BTreeMap::new();
        obj1.insert("a".to_string(), ParsedContent::Integer(1));

        let mut obj2 = BTreeMap::new();
        obj2.insert("b".to_string(), ParsedContent::Integer(2));

        let result = loader.merge(vec![
            ParsedContent::Object(obj1),
            ParsedContent::Object(obj2),
        ]);

        assert!(result.get("a").is_some());
        assert!(result.get("b").is_some());
    }

    #[test]
    fn test_loader_to_type() {
        use serde::Deserialize;

        #[derive(Debug, Deserialize, PartialEq)]
        struct Config {
            name: String,
        }

        let loader = Loader::new();

        let mut obj = BTreeMap::new();
        obj.insert(
            "name".to_string(),
            ParsedContent::String("test".to_string()),
        );
        let content = ParsedContent::Object(obj);

        let config: Config = loader.to_type(content).unwrap();
        assert_eq!(config.name, "test");
    }

    #[test]
    fn test_loader_load_multiple() {
        let source1 = TestSource::new(r#"{"a": 1}"#, Format::Json);
        let source2 = TestSource::new(r#"{"b": 2}"#, Format::Json);

        let loader = Loader::builder()
            .merge_strategy(MergeStrategy::Deep)
            .build();

        let result = loader.load_multiple(&[source1, source2]).unwrap();
        assert!(result.get("a").is_some());
        assert!(result.get("b").is_some());
    }

    #[test]
    fn test_loader_load_multiple_with_optional() {
        let source1 = TestSource::new(r#"{"a": 1}"#, Format::Json);
        let source2 = TestSource::new(r"invalid", Format::Toml).with_optional(true);

        let loader = Loader::builder().fail_fast(false).build();

        // Should succeed because optional source failure is ignored
        let result = loader.load_multiple(&[source1, source2]).unwrap();
        assert!(result.get("a").is_some());
    }

    #[test]
    fn test_loader_default_format() {
        let source = TestSource::new(r#"{"key": "value"}"#, Format::Unknown);

        let loader = Loader::builder().default_format(Format::Json).build();

        let content = loader.load(&source).unwrap();
        assert!(content.is_object());
    }
}