use crate::watcher::{EventSource, SystemEvent};
use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

#[derive(Debug, Clone, Deserialize)]
pub struct PatternMeta {
    pub source_os: String,
    pub target_distro_family: String,
}

#[derive(Debug, Clone, Deserialize)]
pub struct Pattern {
    pub id: String,
    pub sources: Vec<String>,
    pub match_text: String,
    pub severity: String,
    pub title: String,
    pub body: String,
}

#[derive(Debug, Clone, Deserialize)]
pub struct PatternFile {
    pub meta: PatternMeta,
    #[serde(default)]
    pub log_paths: HashMap<String, String>,
    #[serde(default)]
    pub patterns: Vec<Pattern>,
}

#[derive(Debug, Clone, Serialize)]
pub struct MatchedEvent {
    pub pattern_id: String,
    pub title: String,
    pub body: String,
    pub severity: String,
    pub timestamp: u64,
}

/// Load the pattern file for a source OS and distro family.
///
/// Tries candidates in order: dev-relative path, src-tauri-relative path,
/// system path. The Tauri resource directory is the authoritative location
/// at runtime; passing a base path is handled in Task 10's caller via candidate list.
pub fn load(source_os: &str, distro_family: &str) -> Result<PatternFile> {
    let filename = format!("{source_os}-to-{distro_family}.toml");
    let candidates = [
        format!("patterns/{filename}"),
        format!("src-tauri/patterns/{filename}"),
        format!("/usr/share/robin/patterns/{filename}"),
    ];
    for path in &candidates {
        if let Ok(content) = std::fs::read_to_string(path) {
            let pf: PatternFile =
                toml::from_str(&content).with_context(|| format!("failed to parse {path}"))?;
            for p in &pf.patterns {
                anyhow::ensure!(
                    !p.match_text.is_empty(),
                    "pattern '{}' has empty match_text in {path}",
                    p.id
                );
                anyhow::ensure!(
                    !p.sources.is_empty(),
                    "pattern '{}' has empty sources list in {path}",
                    p.id
                );
            }
            return Ok(pf);
        }
    }
    anyhow::bail!("pattern file not found: {filename}")
}

#[must_use]
pub fn classify(event: &SystemEvent, pf: &PatternFile) -> Option<MatchedEvent> {
    for pattern in &pf.patterns {
        if !event.raw_line.contains(&pattern.match_text) {
            continue;
        }

        let source_matches = pattern.sources.iter().any(|s| {
            if s == "any" {
                return true;
            }
            match &event.source {
                EventSource::Journald => s == "journald",
                EventSource::Kmsg => s == "kmsg",
                EventSource::AppLog { app } => s == &format!("applog:{app}"),
            }
        });

        if source_matches {
            return Some(MatchedEvent {
                pattern_id: pattern.id.clone(),
                title: pattern.title.clone(),
                body: pattern.body.clone(),
                severity: pattern.severity.clone(),
                timestamp: event.timestamp,
            });
        }
    }
    None
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::watcher::{EventSource, SystemEvent};

    const FIXTURE: &str = r#"
[meta]
source_os = "macos"
target_distro_family = "arch"

[log_paths]
steam = "~/.local/share/Steam/logs/content_log.txt"

[[patterns]]
id = "aur-build-failure"
sources = ["journald"]
match_text = "error: failed to build"
severity = "warn"
title = "AUR package build failed"
body = "A package failed to compile from source."

[[patterns]]
id = "proton-runtime"
sources = ["applog:steam"]
match_text = "wine: cannot find"
severity = "warn"
title = "Proton runtime issue"
body = "Steam Proton couldn't find a required file."

[[patterns]]
id = "any-source-pattern"
sources = ["any"]
match_text = "kernel panic"
severity = "crit"
title = "Kernel panic"
body = "The kernel encountered a fatal error."
"#;

    fn make_event(source: EventSource, raw_line: &str) -> SystemEvent {
        SystemEvent {
            source,
            raw_line: raw_line.into(),
            timestamp: 0,
        }
    }

    #[test]
    fn loads_pattern_file_from_toml() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        assert_eq!(pf.meta.source_os, "macos");
        assert_eq!(pf.patterns.len(), 3);
        assert_eq!(
            pf.log_paths.get("steam").unwrap(),
            "~/.local/share/Steam/logs/content_log.txt"
        );
    }

    #[test]
    fn classify_matches_journald_event() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(EventSource::Journald, ":: error: failed to build (foo-git)");
        let matched = classify(&event, &pf).unwrap();
        assert_eq!(matched.pattern_id, "aur-build-failure");
        assert_eq!(matched.title, "AUR package build failed");
    }

    #[test]
    fn classify_no_match_returns_none() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(
            EventSource::Journald,
            "systemd: Started NetworkManager.service",
        );
        assert!(classify(&event, &pf).is_none());
    }

    #[test]
    fn classify_applog_matches_correct_source() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(
            EventSource::AppLog {
                app: "steam".into(),
            },
            "wine: cannot find /run/media/user/game.exe",
        );
        let matched = classify(&event, &pf).unwrap();
        assert_eq!(matched.pattern_id, "proton-runtime");
    }

    #[test]
    fn classify_does_not_match_wrong_source() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        // proton pattern is applog:steam — journald event must not match
        let event = make_event(EventSource::Journald, "wine: cannot find something");
        assert!(classify(&event, &pf).is_none());
    }

    #[test]
    fn classify_applog_does_not_match_different_app() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(
            EventSource::AppLog {
                app: "retroarch".into(),
            },
            "wine: cannot find libvulkan.so",
        );
        assert!(classify(&event, &pf).is_none());
    }

    #[test]
    fn classify_any_source_matches_kmsg() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(EventSource::Kmsg, "kernel panic - not syncing: VFS");
        let matched = classify(&event, &pf).unwrap();
        assert_eq!(matched.pattern_id, "any-source-pattern");
    }

    #[test]
    fn classify_any_source_matches_journald() {
        let pf: PatternFile = toml::from_str(FIXTURE).unwrap();
        let event = make_event(EventSource::Journald, "kernel panic - not syncing: VFS");
        let matched = classify(&event, &pf).unwrap();
        assert_eq!(matched.pattern_id, "any-source-pattern");
    }

    #[test]
    fn load_rejects_empty_match_text() {
        let bad = r#"
[meta]
source_os = "macos"
target_distro_family = "arch"

[[patterns]]
id = "bad"
sources = ["journald"]
match_text = ""
severity = "warn"
title = "Bad"
body = "Bad pattern."
"#;
        let pf: PatternFile = toml::from_str(bad).unwrap();
        // Validate manually since load() reads from filesystem; test the invariant directly
        let result: anyhow::Result<()> = (|| {
            for p in &pf.patterns {
                anyhow::ensure!(!p.match_text.is_empty(), "empty match_text in '{}'", p.id);
            }
            Ok(())
        })();
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("empty match_text"));
    }

    #[test]
    fn load_rejects_empty_sources() {
        let bad = r#"
[meta]
source_os = "macos"
target_distro_family = "arch"

[[patterns]]
id = "bad"
sources = []
match_text = "something"
severity = "warn"
title = "Bad"
body = "Bad pattern."
"#;
        let pf: PatternFile = toml::from_str(bad).unwrap();
        let result: anyhow::Result<()> = (|| {
            for p in &pf.patterns {
                anyhow::ensure!(!p.sources.is_empty(), "empty sources in '{}'", p.id);
            }
            Ok(())
        })();
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("empty sources"));
    }
}