use crate::config::Settings;
use eyre::{Result, bail};
use std::fmt;

/// Represents a target platform for lockfile operations
#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Platform {
    pub os: String,
    pub arch: String,
    pub qualifier: Option<String>,
}

impl Platform {
    /// Parse a platform string in the format "os-arch" or "os-arch-qualifier"
    /// Qualifier may contain hyphens (e.g., "musl-baseline")
    pub fn parse(platform_str: &str) -> Result<Self> {
        let parts: Vec<&str> = platform_str.split('-').collect();

        match parts.len() {
            0 | 1 => bail!(
                "Invalid platform format '{}'. Expected 'os-arch' or 'os-arch-qualifier'",
                platform_str
            ),
            2 => Ok(Platform {
                os: parts[0].to_string(),
                arch: parts[1].to_string(),
                qualifier: None,
            }),
            _ => {
                // Join remaining parts as qualifier (handles compound qualifiers like "musl-baseline")
                let qualifier = parts[2..].join("-");
                Ok(Platform {
                    os: parts[0].to_string(),
                    arch: parts[1].to_string(),
                    qualifier: Some(qualifier),
                })
            }
        }
    }

    /// Get the current platform from system information.
    /// On Linux, detects musl vs glibc at runtime and sets the qualifier accordingly.
    pub fn current() -> Self {
        let settings = Settings::get();
        let os = settings.os().to_string();
        let qualifier = if os == "linux" && is_musl_system() {
            Some("musl".to_string())
        } else {
            None
        };
        Platform {
            os,
            arch: settings.arch().to_string(),
            qualifier,
        }
    }

    /// Validate that this platform is supported
    pub fn validate(&self) -> Result<()> {
        // Validate OS
        match self.os.as_str() {
            "linux" | "macos" | "windows" => {}
            _ => bail!(
                "Unsupported OS '{}'. Supported: linux, macos, windows",
                self.os
            ),
        }

        // Validate architecture
        match self.arch.as_str() {
            "x64" | "arm64" | "x86" => {}
            _ => bail!(
                "Unsupported architecture '{}'. Supported: x64, arm64, x86",
                self.arch
            ),
        }

        // Validate qualifier if present
        if let Some(qualifier) = &self.qualifier {
            match qualifier.as_str() {
                "gnu" | "musl" | "msvc" | "baseline" | "musl-baseline" => {}
                _ => bail!(
                    "Unsupported qualifier '{}'. Supported: gnu, musl, msvc, baseline, musl-baseline",
                    qualifier
                ),
            }
        }

        Ok(())
    }

    /// Check if this platform is compatible with the current system
    pub fn is_compatible_with_current(&self) -> bool {
        let current = Self::current();
        self.os == current.os && self.arch == current.arch
    }

    /// Convert to platform key format used in lockfiles
    pub fn to_key(&self) -> String {
        match &self.qualifier {
            Some(qualifier) => format!("{}-{}-{}", self.os, self.arch, qualifier),
            None => format!("{}-{}", self.os, self.arch),
        }
    }

    /// Parse multiple platform strings, validating each one
    pub fn parse_multiple(platform_strings: &[String]) -> Result<Vec<Self>> {
        let mut platforms = Vec::new();

        for platform_str in platform_strings {
            let platform = Self::parse(platform_str)?;
            platform.validate()?;
            platforms.push(platform);
        }

        // Remove duplicates and sort
        platforms.sort();
        platforms.dedup();

        Ok(platforms)
    }

    /// Get a list of commonly supported platforms
    pub fn common_platforms() -> Vec<Self> {
        vec![
            Platform::parse("linux-x64").unwrap(),
            Platform::parse("linux-x64-musl").unwrap(),
            Platform::parse("linux-arm64").unwrap(),
            Platform::parse("linux-arm64-musl").unwrap(),
            Platform::parse("macos-x64").unwrap(),
            Platform::parse("macos-arm64").unwrap(),
            Platform::parse("windows-x64").unwrap(),
        ]
    }

    /// Check if this is a Windows platform
    pub fn is_windows(&self) -> bool {
        self.os == "windows"
    }

    /// Check if this is a macOS platform
    pub fn is_macos(&self) -> bool {
        self.os == "macos"
    }

    /// Check if this is a Linux platform
    pub fn is_linux(&self) -> bool {
        self.os == "linux"
    }

    /// Check if this uses ARM64 architecture
    pub fn is_arm64(&self) -> bool {
        self.arch == "arm64"
    }

    /// Check if this uses x64 architecture
    pub fn is_x64(&self) -> bool {
        self.arch == "x64"
    }
}

impl fmt::Display for Platform {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.to_key())
    }
}

impl From<String> for Platform {
    fn from(s: String) -> Self {
        Self::parse(&s).unwrap_or_else(|_| {
            // Fallback to current platform if parsing fails
            Self::current()
        })
    }
}

impl From<&str> for Platform {
    fn from(s: &str) -> Self {
        Self::parse(s).unwrap_or_else(|_| {
            // Fallback to current platform if parsing fails
            Self::current()
        })
    }
}

/// Detect whether the system uses musl libc at runtime.
/// Checks for the absence of glibc's dynamic linker (`ld-linux-*`) in /lib and /lib64.
/// On glibc systems, `ld-linux-*` is always present (even if musl-tools is installed
/// for cross-compilation, which also places `ld-musl-*` in /lib). On musl-only systems
/// (Alpine, Void musl, etc.), only `ld-musl-*` exists without `ld-linux-*`.
// NOTE: This logic is mirrored in crates/vfox/src/config.rs env_type(). Keep in sync.
#[cfg(target_os = "linux")]
fn is_musl_system() -> bool {
    use std::sync::LazyLock;
    static IS_MUSL: LazyLock<bool> = LazyLock::new(|| {
        // Allow explicit override via environment variable (only gnu/musl accepted)
        if let Ok(val) = std::env::var("MISE_LIBC") {
            match val.to_lowercase().as_str() {
                "musl" => return true,
                "gnu" => return false,
                _ => {} // invalid value ignored, fall through to runtime detection
            }
        }
        // If glibc's dynamic linker exists, this is a glibc system
        for dir in ["/lib", "/lib64"] {
            if has_file_prefix(dir, "ld-linux-") {
                return false;
            }
        }
        // No glibc linker found — check for musl's
        for dir in ["/lib", "/lib64"] {
            if has_file_prefix(dir, "ld-musl-") {
                return true;
            }
        }
        // No linker found at all (e.g., scratch/busybox container) —
        // fall back to the binary's compile-time target
        cfg!(target_env = "musl")
    });
    *IS_MUSL
}

#[cfg(target_os = "linux")]
fn has_file_prefix(dir: &str, prefix: &str) -> bool {
    std::fs::read_dir(dir)
        .map(|entries| {
            entries
                .flatten()
                .any(|e| e.file_name().to_string_lossy().starts_with(prefix))
        })
        .unwrap_or(false)
}

#[cfg(not(target_os = "linux"))]
fn is_musl_system() -> bool {
    false
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_platform_parse_basic() {
        let platform = Platform::parse("linux-x64").unwrap();
        assert_eq!(platform.os, "linux");
        assert_eq!(platform.arch, "x64");
        assert_eq!(platform.qualifier, None);
    }

    #[test]
    fn test_platform_parse_with_qualifier() {
        let platform = Platform::parse("linux-x64-gnu").unwrap();
        assert_eq!(platform.os, "linux");
        assert_eq!(platform.arch, "x64");
        assert_eq!(platform.qualifier, Some("gnu".to_string()));
    }

    #[test]
    fn test_platform_parse_with_compound_qualifier() {
        // Compound qualifiers like "musl-baseline" should parse correctly
        let platform = Platform::parse("linux-x64-musl-baseline").unwrap();
        assert_eq!(platform.os, "linux");
        assert_eq!(platform.arch, "x64");
        assert_eq!(platform.qualifier, Some("musl-baseline".to_string()));

        // Verify round-trip: parse -> to_key -> parse
        assert_eq!(platform.to_key(), "linux-x64-musl-baseline");
        let reparsed = Platform::parse(&platform.to_key()).unwrap();
        assert_eq!(reparsed.qualifier, Some("musl-baseline".to_string()));
    }

    #[test]
    fn test_platform_parse_invalid() {
        assert!(Platform::parse("linux").is_err());
        assert!(Platform::parse("").is_err());
    }

    #[test]
    fn test_platform_validation() {
        // Valid platforms
        assert!(Platform::parse("linux-x64").unwrap().validate().is_ok());
        assert!(Platform::parse("macos-arm64").unwrap().validate().is_ok());
        assert!(Platform::parse("windows-x64").unwrap().validate().is_ok());
        assert!(Platform::parse("linux-x64-gnu").unwrap().validate().is_ok());

        // Invalid OS
        assert!(Platform::parse("invalid-x64").unwrap().validate().is_err());

        // Invalid arch
        assert!(
            Platform::parse("linux-invalid")
                .unwrap()
                .validate()
                .is_err()
        );

        // Invalid qualifier
        assert!(
            Platform::parse("linux-x64-invalid")
                .unwrap()
                .validate()
                .is_err()
        );
    }

    #[test]
    fn test_platform_to_key() {
        let platform1 = Platform::parse("linux-x64").unwrap();
        assert_eq!(platform1.to_key(), "linux-x64");

        let platform2 = Platform::parse("linux-x64-gnu").unwrap();
        assert_eq!(platform2.to_key(), "linux-x64-gnu");
    }

    #[test]
    fn test_platform_multiple_parsing() {
        let platform_strings = vec![
            "linux-x64".to_string(),
            "macos-arm64".to_string(),
            "linux-x64".to_string(), // duplicate should be removed
        ];

        let platforms = Platform::parse_multiple(&platform_strings).unwrap();
        assert_eq!(platforms.len(), 2);
        assert_eq!(platforms[0].to_key(), "linux-x64");
        assert_eq!(platforms[1].to_key(), "macos-arm64");
    }

    #[test]
    fn test_platform_helpers() {
        let linux_platform = Platform::parse("linux-arm64").unwrap();
        assert!(linux_platform.is_linux());
        assert!(linux_platform.is_arm64());
        assert!(!linux_platform.is_windows());
        assert!(!linux_platform.is_x64());

        let windows_platform = Platform::parse("windows-x64").unwrap();
        assert!(windows_platform.is_windows());
        assert!(windows_platform.is_x64());
        assert!(!windows_platform.is_linux());
        assert!(!windows_platform.is_arm64());
    }

    #[test]
    fn test_common_platforms() {
        let platforms = Platform::common_platforms();
        assert_eq!(platforms.len(), 7);

        let keys: Vec<String> = platforms.iter().map(|p| p.to_key()).collect();
        assert!(keys.contains(&"linux-x64".to_string()));
        assert!(keys.contains(&"linux-x64-musl".to_string()));
        assert!(keys.contains(&"linux-arm64".to_string()));
        assert!(keys.contains(&"linux-arm64-musl".to_string()));
        assert!(keys.contains(&"macos-x64".to_string()));
        assert!(keys.contains(&"macos-arm64".to_string()));
        assert!(keys.contains(&"windows-x64".to_string()));
    }

    #[cfg(all(target_os = "linux", target_env = "musl"))]
    #[test]
    fn test_musl_binary_detects_musl() {
        // A musl-compiled binary should always detect musl, even in
        // minimal containers with no linker files (scratch, busybox).
        assert!(
            is_musl_system(),
            "musl-compiled binary should detect musl system"
        );
    }

    #[cfg(all(target_os = "linux", target_env = "musl"))]
    #[test]
    fn test_current_platform_has_musl_qualifier() {
        // A musl-compiled binary should always have the musl qualifier,
        // even in minimal containers with no linker files.
        let platform = Platform::current();
        assert_eq!(
            platform.qualifier.as_deref(),
            Some("musl"),
            "musl-compiled binary should have musl qualifier, got: {}",
            platform.to_key()
        );
    }
}
