//! Read the user's plan tier from `~/.claude/` and map it to approximate
//! cap values.
//!
//! These caps are *approximations* based on community-shared observations —
//! Anthropic does not publish the exact 5-hour / weekly token caps, and they
//! shift over time. The widget shows a percentage off these caps, but
//! anything within ±20% of "the real number" is fine for a desktop heads-up
//! display. Users tune them in Settings once they hit a real limit.

use crate::settings::Caps;
use serde::Serialize;
use std::path::PathBuf;

#[derive(Debug, Clone, Serialize, PartialEq, Eq)]
pub enum PlanTier {
    Pro,
    Max5x,
    Max20x,
    /// Tier string we recognized as Max but couldn't sub-classify.
    MaxOther(String),
    /// The on-disk string was something we don't have a mapping for.
    Unknown(String),
    /// No `.claude.json` (or backup) found, or the field was missing.
    NotFound,
}

impl PlanTier {
    pub fn caps(&self) -> Caps {
        match self {
            // Rough numbers, deliberately on the generous side so the ring
            // doesn't peg red on day one. Tune in Settings when reality hits.
            PlanTier::Max20x => Caps { block_tokens: 200_000_000, weekly_tokens: 1_000_000_000 },
            PlanTier::Max5x | PlanTier::MaxOther(_) => Caps {
                block_tokens: 50_000_000,
                weekly_tokens: 250_000_000,
            },
            PlanTier::Pro => Caps { block_tokens: 10_000_000, weekly_tokens: 50_000_000 },
            // Fall back to the safe (and visibly wrong) placeholders so the
            // user knows they need to tune. Better than guessing.
            PlanTier::Unknown(_) | PlanTier::NotFound => Caps::default(),
        }
    }

    pub fn label(&self) -> String {
        match self {
            PlanTier::Pro => "Pro".to_string(),
            PlanTier::Max5x => "Max 5×".to_string(),
            PlanTier::Max20x => "Max 20×".to_string(),
            PlanTier::MaxOther(s) => format!("Max ({s})"),
            PlanTier::Unknown(s) => format!("Unknown ({s})"),
            PlanTier::NotFound => "Unknown".to_string(),
        }
    }
}

/// Parse a raw tier string (the value of `organizationRateLimitTier` in
/// `.claude.json`) into a known tier.
fn classify(raw: &str) -> PlanTier {
    let l = raw.to_lowercase();
    if l.contains("max_20x") || l.contains("max20x") {
        PlanTier::Max20x
    } else if l.contains("max_5x") || l.contains("max5x") {
        PlanTier::Max5x
    } else if l.contains("max") {
        PlanTier::MaxOther(raw.to_string())
    } else if l.contains("pro") {
        PlanTier::Pro
    } else {
        PlanTier::Unknown(raw.to_string())
    }
}

/// Read the tier from a single `.claude.json`-shaped file. None if the file
/// doesn't exist, isn't valid JSON, or is missing the field.
fn read_tier_from(path: &std::path::Path) -> Option<PlanTier> {
    let bytes = std::fs::read(path).ok()?;
    let json: serde_json::Value = serde_json::from_slice(&bytes).ok()?;
    let raw = json.get("organizationRateLimitTier").and_then(|v| v.as_str())?;
    Some(classify(raw))
}

/// Same as [`read_tier_from`] but returns a string describing what happened.
/// Used for the diagnostic `searched` list in TierInfo.
fn probe_tier_file(path: &std::path::Path) -> String {
    match std::fs::read(path) {
        Err(e) => format!("read_err: {}", e.kind()),
        Ok(bytes) => match serde_json::from_slice::<serde_json::Value>(&bytes) {
            Err(_) => format!("not_json (size={})", bytes.len()),
            Ok(json) => match json.get("organizationRateLimitTier").and_then(|v| v.as_str()) {
                None => format!("no_tier_field (size={})", bytes.len()),
                Some(raw) => format!("OK: {}", raw),
            },
        },
    }
}

/// Try each `.claude/` candidate directory in order. The first hit wins.
///
/// For each candidate `<dir>` we look at:
///   1. `<dir>/.claude.json`               (e.g. ~/.claude/.claude.json)
///   2. `<dir>/backups/.claude.json.backup.*` (newest)
///   3. `<parent of dir>/.claude.json`     (some setups put it at ~/.claude.json)
pub fn detect_in(claude_dirs: &[PathBuf]) -> PlanTier {
    let (tier, _) = detect_in_with_diagnostics(claude_dirs);
    tier
}

/// Like [`detect_in`] but also returns one diagnostic line per probed path
/// describing what happened (for surfacing in the Settings UI).
pub fn detect_in_with_diagnostics(
    claude_dirs: &[PathBuf],
) -> (PlanTier, Vec<String>) {
    let mut diag: Vec<String> = Vec::new();
    let mut found: Option<PlanTier> = None;

    for dir in claude_dirs {
        let primary = dir.join(".claude.json");
        let result = probe_tier_file(&primary);
        diag.push(format!("{} → {}", primary.display(), result));
        if found.is_none() {
            if let Some(t) = read_tier_from(&primary) {
                found = Some(t);
            }
        }

        let backups = dir.join("backups");
        match newest_backup(&backups) {
            Err(e) => diag.push(format!("{} → readdir_err: {}", backups.display(), e)),
            Ok(None) => diag.push(format!("{} → no_backups", backups.display())),
            Ok(Some(p)) => {
                let result = probe_tier_file(&p);
                diag.push(format!("{} → {}", p.display(), result));
                if found.is_none() {
                    if let Some(t) = read_tier_from(&p) {
                        found = Some(t);
                    }
                }
            }
        }

        if let Some(parent) = dir.parent() {
            let alt = parent.join(".claude.json");
            let result = probe_tier_file(&alt);
            diag.push(format!("{} → {}", alt.display(), result));
            if found.is_none() {
                if let Some(t) = read_tier_from(&alt) {
                    found = Some(t);
                }
            }
        }
    }

    (found.unwrap_or(PlanTier::NotFound), diag)
}

fn newest_backup(dir: &std::path::Path) -> std::io::Result<Option<PathBuf>> {
    let entries = std::fs::read_dir(dir)?;
    let mut latest: Option<(std::time::SystemTime, PathBuf)> = None;
    for entry in entries.flatten() {
        let path = entry.path();
        let name = path.file_name().and_then(|s| s.to_str()).unwrap_or("");
        if !name.starts_with(".claude.json.backup.") {
            continue;
        }
        if let Ok(meta) = entry.metadata() {
            if let Ok(mtime) = meta.modified() {
                match &latest {
                    None => latest = Some((mtime, path)),
                    Some((m, _)) if mtime > *m => latest = Some((mtime, path)),
                    _ => {}
                }
            }
        }
    }
    Ok(latest.map(|(_, p)| p))
}

/// Native-only fallback path. Most callers should prefer `detect_in` with
/// the resolved-roots' parents so the WSL case works.
#[allow(dead_code)]
pub fn detect() -> PlanTier {
    let Some(home) = dirs::home_dir() else {
        return PlanTier::NotFound;
    };
    detect_in(&[home.join(".claude")])
}

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

    #[test]
    fn classifies_known_tiers() {
        assert_eq!(classify("default_claude_max_5x"), PlanTier::Max5x);
        assert_eq!(classify("default_claude_max_20x"), PlanTier::Max20x);
        assert_eq!(classify("default_claude_pro"), PlanTier::Pro);
        assert!(matches!(classify("default_claude_max_99x"), PlanTier::MaxOther(_)));
        assert!(matches!(classify("anything-else"), PlanTier::Unknown(_)));
    }

    #[test]
    fn caps_scale_by_tier() {
        assert!(PlanTier::Max20x.caps().block_tokens > PlanTier::Max5x.caps().block_tokens);
        assert!(PlanTier::Max5x.caps().block_tokens > PlanTier::Pro.caps().block_tokens);
        assert!(PlanTier::Pro.caps().block_tokens > PlanTier::NotFound.caps().block_tokens);
    }
}