use crate::config::BuildOverrides;
use anyhow::{Context as _, Result, bail};
use serde::Deserialize;
use std::path::{Component, Path};

/// Configuration for building a site, read from `witryna.yaml` or `witryna.yml` in the repository root.
#[derive(Debug, Deserialize)]
pub struct RepoConfig {
    /// Container image to use for building (e.g., "node:20-alpine").
    pub image: String,
    /// Command to execute inside the container (e.g., "npm install && npm run build")
    pub command: String,
    /// Directory containing built static assets, relative to repo root (e.g., "dist")
    pub public: String,
}

/// Validate container image name.
///
/// # Errors
///
/// Returns an error if the image name is empty or whitespace-only.
pub fn validate_image(image: &str) -> Result<()> {
    if image.trim().is_empty() {
        bail!("image cannot be empty");
    }
    Ok(())
}

/// Validate build command.
///
/// # Errors
///
/// Returns an error if the command is empty or whitespace-only.
pub fn validate_command(command: &str) -> Result<()> {
    if command.trim().is_empty() {
        bail!("command cannot be empty");
    }
    Ok(())
}

/// Validate public directory path.
///
/// # Errors
///
/// Returns an error if the path is empty, contains path traversal segments,
/// or is an absolute path.
pub fn validate_public(public: &str) -> Result<()> {
    if public.trim().is_empty() {
        bail!("public directory cannot be empty");
    }

    // OWASP: Reject absolute paths
    if public.starts_with('/') {
        bail!("invalid public directory '{public}': must be a relative path");
    }

    // OWASP: Reject real path traversal (Component::ParentDir)
    // Allows names like "dist..v2" which contain ".." but are not traversal
    if Path::new(public)
        .components()
        .any(|c| c == Component::ParentDir)
    {
        bail!("invalid public directory '{public}': path traversal not allowed");
    }

    Ok(())
}

impl RepoConfig {
    /// Load repo configuration from the given repository directory.
    ///
    /// If `config_file` is `Some`, reads that specific path (relative to repo root).
    /// Otherwise searches: `.witryna.yaml` -> `.witryna.yml` -> `witryna.yaml` -> `witryna.yml`.
    ///
    /// # Errors
    ///
    /// Returns an error if no config file is found, the file cannot be read
    /// or parsed, or validation fails.
    pub async fn load(repo_dir: &Path, config_file: Option<&str>) -> Result<Self> {
        if let Some(custom) = config_file {
            let path = repo_dir.join(custom);
            let content = tokio::fs::read_to_string(&path)
                .await
                .with_context(|| format!("failed to read {}", path.display()))?;
            let config: Self = serde_yaml_ng::from_str(&content)
                .with_context(|| format!("failed to parse {}", path.display()))?;
            config.validate()?;
            return Ok(config);
        }

        let candidates = [
            ".witryna.yaml",
            ".witryna.yml",
            "witryna.yaml",
            "witryna.yml",
        ];
        for name in candidates {
            let path = repo_dir.join(name);
            if path.exists() {
                let content = tokio::fs::read_to_string(&path)
                    .await
                    .with_context(|| format!("failed to read {}", path.display()))?;
                let config: Self = serde_yaml_ng::from_str(&content)
                    .with_context(|| format!("failed to parse {}", path.display()))?;
                config.validate()?;
                return Ok(config);
            }
        }
        bail!(
            "no build config found in {} (tried: {})",
            repo_dir.display(),
            candidates.join(", ")
        );
    }

    fn validate(&self) -> Result<()> {
        validate_image(&self.image)?;
        validate_command(&self.command)?;
        validate_public(&self.public)?;
        Ok(())
    }

    /// Load repo configuration, applying overrides from witryna.toml.
    ///
    /// If all three override fields are specified, witryna.yaml is not loaded.
    /// Otherwise, loads witryna.yaml and applies any partial overrides.
    ///
    /// # Errors
    ///
    /// Returns an error if the base config cannot be loaded (when overrides
    /// are incomplete) or validation fails.
    ///
    /// # Panics
    ///
    /// Panics if `is_complete()` returns true but a required override
    /// field is `None`. This is unreachable because `is_complete()`
    /// checks all required fields.
    #[allow(clippy::expect_used)] // fields verified by is_complete()
    pub async fn load_with_overrides(
        repo_dir: &Path,
        overrides: &BuildOverrides,
        config_file: Option<&str>,
    ) -> Result<Self> {
        // If all overrides are specified, skip loading witryna.yaml
        if overrides.is_complete() {
            let config = Self {
                image: overrides.image.clone().expect("verified by is_complete"),
                command: overrides.command.clone().expect("verified by is_complete"),
                public: overrides.public.clone().expect("verified by is_complete"),
            };
            // Validation already done in SiteConfig::validate(), but validate again for safety
            config.validate()?;
            return Ok(config);
        }

        // Load base config from repo
        let mut config = Self::load(repo_dir, config_file).await?;

        // Apply overrides (already validated in SiteConfig)
        if let Some(image) = &overrides.image {
            config.image.clone_from(image);
        }
        if let Some(command) = &overrides.command {
            config.command.clone_from(command);
        }
        if let Some(public) = &overrides.public {
            config.public.clone_from(public);
        }

        Ok(config)
    }
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::indexing_slicing)]
mod tests {
    use super::*;
    use crate::test_support::{cleanup, temp_dir};

    fn parse_yaml(yaml: &str) -> Result<RepoConfig> {
        let config: RepoConfig = serde_yaml_ng::from_str(yaml)?;
        config.validate()?;
        Ok(config)
    }

    #[test]
    fn parse_valid_repo_config() {
        let yaml = r#"
image: "node:20-alpine"
command: "npm install && npm run build"
public: "dist"
"#;
        let config = parse_yaml(yaml).unwrap();
        assert_eq!(config.image, "node:20-alpine");
        assert_eq!(config.command, "npm install && npm run build");
        assert_eq!(config.public, "dist");
    }

    #[test]
    fn missing_required_field() {
        let yaml = r#"
image: "node:20-alpine"
command: "npm run build"
"#;
        let result: Result<RepoConfig, _> = serde_yaml_ng::from_str(yaml);
        assert!(result.is_err());
    }

    #[test]
    fn empty_or_whitespace_image_rejected() {
        for image in ["", "   "] {
            let yaml =
                format!("image: \"{image}\"\ncommand: \"npm run build\"\npublic: \"dist\"\n");
            let result = parse_yaml(&yaml);
            assert!(result.is_err(), "image '{image}' should be rejected");
            assert!(result.unwrap_err().to_string().contains("image"));
        }
    }

    #[test]
    fn empty_command() {
        let yaml = r#"
image: "node:20-alpine"
command: ""
public: "dist"
"#;
        let result = parse_yaml(yaml);
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("command"));
    }

    #[test]
    fn empty_public() {
        let yaml = r#"
image: "node:20-alpine"
command: "npm run build"
public: ""
"#;
        let result = parse_yaml(yaml);
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("public"));
    }

    #[test]
    fn public_path_traversal() {
        let invalid_paths = vec!["../dist", "build/../dist", "dist/..", ".."];

        for path in invalid_paths {
            let yaml = format!(
                r#"
image: "node:20-alpine"
command: "npm run build"
public: "{path}"
"#
            );
            let result = parse_yaml(&yaml);
            assert!(result.is_err(), "public path '{path}' should be rejected");
            assert!(result.unwrap_err().to_string().contains("path traversal"));
        }
    }

    #[test]
    fn public_absolute_path_unix() {
        let invalid_paths = vec!["/dist", "/var/www/dist"];

        for path in invalid_paths {
            let yaml = format!(
                r#"
image: "node:20-alpine"
command: "npm run build"
public: "{path}"
"#
            );
            let result = parse_yaml(&yaml);
            assert!(result.is_err(), "public path '{path}' should be rejected");
            assert!(result.unwrap_err().to_string().contains("relative path"));
        }
    }

    #[test]
    fn valid_nested_public() {
        let valid_paths = vec![
            "dist",
            "build/dist",
            "out/static",
            "_site",
            ".next/out",
            "dist..v2",
            "assets/..hidden",
            "foo..bar/dist",
        ];

        for path in valid_paths {
            let yaml = format!(
                r#"
image: "node:20-alpine"
command: "npm run build"
public: "{path}"
"#
            );
            let result = parse_yaml(&yaml);
            assert!(result.is_ok(), "public path '{path}' should be valid");
        }
    }

    #[test]
    fn public_dot_segments_accepted() {
        let valid = vec![".", "./dist", "dist/.", "dist//assets"];
        for path in valid {
            assert!(
                validate_public(path).is_ok(),
                "path '{path}' should be valid"
            );
        }
    }

    // load_with_overrides tests

    #[tokio::test]
    async fn load_with_overrides_complete_skips_file() {
        // No need to create witryna.yaml since all overrides are provided
        let temp = temp_dir("repo-config-test").await;

        let overrides = BuildOverrides {
            image: Some("alpine:latest".to_owned()),
            command: Some("echo hello".to_owned()),
            public: Some("out".to_owned()),
        };

        let result = RepoConfig::load_with_overrides(&temp, &overrides, None).await;

        assert!(result.is_ok());
        let config = result.unwrap();
        assert_eq!(config.image, "alpine:latest");
        assert_eq!(config.command, "echo hello");
        assert_eq!(config.public, "out");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_with_overrides_partial_merges() {
        let temp = temp_dir("repo-config-test").await;

        // Create witryna.yaml with base config
        let yaml = r#"
image: "node:18"
command: "npm run build"
public: "dist"
"#;
        tokio::fs::write(temp.join("witryna.yaml"), yaml)
            .await
            .unwrap();

        // Override only the image
        let overrides = BuildOverrides {
            image: Some("node:20-alpine".to_owned()),
            command: None,
            public: None,
        };

        let result = RepoConfig::load_with_overrides(&temp, &overrides, None).await;

        assert!(result.is_ok());
        let config = result.unwrap();
        assert_eq!(config.image, "node:20-alpine"); // Overridden
        assert_eq!(config.command, "npm run build"); // From yaml
        assert_eq!(config.public, "dist"); // From yaml

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_with_overrides_none_loads_yaml() {
        let temp = temp_dir("repo-config-test").await;

        // Create witryna.yaml
        let yaml = r#"
image: "node:18"
command: "npm run build"
public: "dist"
"#;
        tokio::fs::write(temp.join("witryna.yaml"), yaml)
            .await
            .unwrap();

        let overrides = BuildOverrides::default();

        let result = RepoConfig::load_with_overrides(&temp, &overrides, None).await;

        assert!(result.is_ok());
        let config = result.unwrap();
        assert_eq!(config.image, "node:18");
        assert_eq!(config.command, "npm run build");
        assert_eq!(config.public, "dist");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_with_overrides_missing_yaml_partial_fails() {
        let temp = temp_dir("repo-config-test").await;

        // No witryna.yaml, partial overrides
        let overrides = BuildOverrides {
            image: Some("node:20-alpine".to_owned()),
            command: None, // Missing, needs yaml
            public: None,
        };

        let result = RepoConfig::load_with_overrides(&temp, &overrides, None).await;

        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("no build config found")
        );

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_with_overrides_incomplete_needs_yaml() {
        let temp = temp_dir("repo-config-test").await;

        // Only command+public — incomplete (no image), no yaml file
        let overrides = BuildOverrides {
            image: None,
            command: Some("npm run build".to_owned()),
            public: Some("dist".to_owned()),
        };

        let result = RepoConfig::load_with_overrides(&temp, &overrides, None).await;

        assert!(result.is_err());
        assert!(
            result
                .unwrap_err()
                .to_string()
                .contains("no build config found")
        );

        cleanup(&temp).await;
    }

    // Discovery chain tests

    const VALID_YAML: &str = "image: \"node:20\"\ncommand: \"npm run build\"\npublic: \"dist\"\n";

    #[tokio::test]
    async fn load_finds_dot_witryna_yaml() {
        let temp = temp_dir("repo-config-test").await;
        tokio::fs::write(temp.join(".witryna.yaml"), VALID_YAML)
            .await
            .unwrap();

        let config = RepoConfig::load(&temp, None).await.unwrap();
        assert_eq!(config.image, "node:20");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_finds_dot_witryna_yml() {
        let temp = temp_dir("repo-config-test").await;
        tokio::fs::write(temp.join(".witryna.yml"), VALID_YAML)
            .await
            .unwrap();

        let config = RepoConfig::load(&temp, None).await.unwrap();
        assert_eq!(config.image, "node:20");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_precedence_dot_over_plain() {
        let temp = temp_dir("repo-config-test").await;
        let dot_yaml = "image: \"dot-image\"\ncommand: \"build\"\npublic: \"out\"\n";
        let plain_yaml = "image: \"plain-image\"\ncommand: \"build\"\npublic: \"out\"\n";
        tokio::fs::write(temp.join(".witryna.yaml"), dot_yaml)
            .await
            .unwrap();
        tokio::fs::write(temp.join("witryna.yaml"), plain_yaml)
            .await
            .unwrap();

        let config = RepoConfig::load(&temp, None).await.unwrap();
        assert_eq!(config.image, "dot-image");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_custom_config_file() {
        let temp = temp_dir("repo-config-test").await;
        let subdir = temp.join("build");
        tokio::fs::create_dir_all(&subdir).await.unwrap();
        tokio::fs::write(subdir.join("config.yml"), VALID_YAML)
            .await
            .unwrap();

        let config = RepoConfig::load(&temp, Some("build/config.yml"))
            .await
            .unwrap();
        assert_eq!(config.image, "node:20");

        cleanup(&temp).await;
    }

    #[tokio::test]
    async fn load_custom_config_file_not_found_errors() {
        let temp = temp_dir("repo-config-test").await;

        let result = RepoConfig::load(&temp, Some("nonexistent.yaml")).await;
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("failed to read"));

        cleanup(&temp).await;
    }
}