//! File-backed harness state, split out of [`crate::events`] (which owns
//! the live event bus + sqlite store). This module holds the runtime
//! model/effort selection and the consolidated `hyperhive-harness.json`
//! state file — the persisted knobs the harness reads/writes across
//! turns, none of which are about the live event stream.

use std::path::PathBuf;

/// Path to the persisted model file. Overridable via `HYPERHIVE_MODEL_FILE`
/// for dev / tests; otherwise derived from the agent's harness dir.
fn model_file_path() -> PathBuf {
    std::env::var_os("HYPERHIVE_MODEL_FILE").map_or_else(
        || crate::paths::harness_dir().join("hyperhive-model"),
        PathBuf::from,
    )
}

pub(crate) fn load_model() -> Option<String> {
    let s = std::fs::read_to_string(model_file_path()).ok()?;
    let name = s.trim();
    if name.is_empty() {
        None
    } else {
        Some(name.to_owned())
    }
}

pub(crate) fn persist_model(name: &str) -> std::io::Result<()> {
    let path = model_file_path();
    if let Some(parent) = path.parent() {
        let _ = std::fs::create_dir_all(parent);
    }
    std::fs::write(path, format!("{name}\n"))
}

/// Path to the persisted effort-level file. Sibling of `hyperhive-model`,
/// overridable via `HYPERHIVE_EFFORT_FILE` for dev / tests; otherwise
/// derived from the agent's harness dir.
fn effort_file_path() -> PathBuf {
    std::env::var_os("HYPERHIVE_EFFORT_FILE").map_or_else(
        || crate::paths::harness_dir().join("hyperhive-effort"),
        PathBuf::from,
    )
}

pub(crate) fn load_effort() -> Option<String> {
    let s = std::fs::read_to_string(effort_file_path()).ok()?;
    let level = s.trim();
    if level.is_empty() {
        None
    } else {
        Some(level.to_owned())
    }
}

pub(crate) fn persist_effort(level: &str) -> std::io::Result<()> {
    let path = effort_file_path();
    if let Some(parent) = path.parent() {
        let _ = std::fs::create_dir_all(parent);
    }
    std::fs::write(path, format!("{level}\n"))
}

// ---------------------------------------------------------------------------
// Consolidated harness state file
// ---------------------------------------------------------------------------
//
// `hyperhive-harness.json` replaces the two legacy boolean sentinel files
// (`hyperhive-rate-limited`, `hyperhive-needs-login`) that grew organically
// and had no shared schema. A single JSON file is self-documenting, atomic
// to write, and cheaper for hive-c0re to read on each sweep (one fopen vs
// two stat calls). See `docs/persistence.md::Harness state files`.
//
// Legacy sentinel files written by older harness builds are still honoured
// by `read_harness_state` so in-place upgrades don't lose state (the new
// harness re-normalises on first write). Old files are not deleted — they
// expire naturally when the state dir is purged. `hive-c0re::container_view`
// also checks the legacy paths as a fallback during the transition window.

const HARNESS_JSON: &str = "hyperhive-harness.json";

fn harness_json_path() -> PathBuf {
    crate::paths::state_dir().join(HARNESS_JSON)
}

// Serialises the read-modify-write of `hyperhive-harness.json`. Every
// writer merges into the existing object rather than reconstructing it,
// so a future second writer preserves fields it doesn't own; the lock
// closes the lost-update window between a writer's read and its rename.
// (The forge poller used to be that second writer, for a delivery-dedupe
// cursor. It no longer persists one — forge's own read-state is the
// durable record — and it is a separate process now, which an
// in-process mutex could not have serialised anyway.)
static HARNESS_JSON_LOCK: std::sync::Mutex<()> = std::sync::Mutex::new(());

/// Read the consolidated state file as a JSON object, or an empty object
/// when it is missing / unparseable / not an object.
fn read_harness_json() -> serde_json::Value {
    std::fs::read_to_string(harness_json_path())
        .ok()
        .and_then(|raw| serde_json::from_str::<serde_json::Value>(&raw).ok())
        .filter(serde_json::Value::is_object)
        .unwrap_or_else(|| serde_json::json!({}))
}

/// Atomically overwrite the state file (`.tmp` + rename) so hive-c0re
/// never reads a partial file.
fn write_harness_json(v: &serde_json::Value) {
    let path = harness_json_path();
    let tmp = path.with_extension("json.tmp");
    if std::fs::write(&tmp, v.to_string()).is_ok() {
        let _ = std::fs::rename(&tmp, &path);
    }
}

pub(crate) fn read_harness_state() -> (bool, bool, Option<String>) {
    // Try the new consolidated file first.
    if let Ok(raw) = std::fs::read_to_string(harness_json_path())
        && let Ok(v) = serde_json::from_str::<serde_json::Value>(&raw)
    {
        let rate_limited = v
            .get("rate_limited")
            .and_then(serde_json::Value::as_bool)
            .unwrap_or(false);
        let needs_login = v
            .get("needs_login")
            .and_then(serde_json::Value::as_bool)
            .unwrap_or(false);
        let active_model = v
            .get("active_model")
            .and_then(serde_json::Value::as_str)
            .filter(|s| !s.is_empty())
            .map(str::to_owned);
        return (rate_limited, needs_login, active_model);
    }
    // Fall back to legacy sentinel files written by older harness builds.
    let state_dir = crate::paths::state_dir();
    let rate_limited = state_dir.join("hyperhive-rate-limited").exists();
    let needs_login = state_dir.join("hyperhive-needs-login").exists();
    (rate_limited, needs_login, None)
}

/// Write the turn-loop's harness state fields via a read-modify-write so
/// any other writer's fields in the consolidated state file survive.
/// Pass `active_model: Some(s)` to update the resolved model (surfaced in
/// the dashboard badge); `None` leaves the stored value untouched.
pub(crate) fn write_harness_state(
    rate_limited: bool,
    needs_login: bool,
    active_model: Option<&str>,
) {
    let _guard = HARNESS_JSON_LOCK
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    let mut v = read_harness_json();
    v["rate_limited"] = rate_limited.into();
    v["needs_login"] = needs_login.into();
    if let Some(model) = active_model {
        v["active_model"] = model.into();
    }
    write_harness_json(&v);
}

/// Compiled-in fallback model used when neither `HIVE_DEFAULT_MODEL` nor a
/// persisted runtime override is present.
pub const DEFAULT_MODEL: &str = "haiku";

/// Return the model declared in `HIVE_DEFAULT_MODEL` (set from
/// `hyperhive.model` in `agent.nix`), or `None` if the env var is absent /
/// empty.  When `Some`, this takes precedence over any persisted runtime
/// override so that nix config changes always take effect on rebuild.
#[must_use]
pub fn configured_model() -> Option<&'static str> {
    // Leak once at startup — acceptable for a single config value.
    std::env::var("HIVE_DEFAULT_MODEL")
        .ok()
        .filter(|s| !s.trim().is_empty())
        .map(|s| &*Box::leak(s.into_boxed_str()))
}

/// Compiled-in fallback effort level — matches the `effortLevel` baked
/// into `prompts/claude-settings.json`.
pub const DEFAULT_EFFORT: &str = "medium";

/// Valid claude `--effort` levels, ascending. The operator picker is
/// constrained to these; [`is_valid_effort`] guards the persist path.
pub const EFFORT_LEVELS: [&str; 5] = ["low", "medium", "high", "xhigh", "max"];

/// True iff `level` is one of [`EFFORT_LEVELS`].
#[must_use]
pub fn is_valid_effort(level: &str) -> bool {
    EFFORT_LEVELS.contains(&level)
}

/// Return the effort level declared in `HIVE_DEFAULT_EFFORT` (set from
/// `hyperhive.effortLevel` in `agent.nix`), or `None` if absent / empty.
/// Mirrors [`configured_model`]'s env shape. Unlike model, the persisted
/// runtime override takes precedence over this baseline (see `Bus::new`):
/// the operator's effort pick sticks across harness restart, with the nix
/// value only the default when no override was ever set.
#[must_use]
pub fn configured_effort() -> Option<&'static str> {
    std::env::var("HIVE_DEFAULT_EFFORT")
        .ok()
        .filter(|s| !s.trim().is_empty())
        .map(|s| &*Box::leak(s.into_boxed_str()))
}

/// Context-window size in tokens for a given model name.
///
/// Canonical per-model sizes are declared in the harness nix modules as
/// `hyperhive.contextWindowTokens` and injected as
/// `HIVE_CONTEXT_WINDOW_TOKENS_<KEY_UPPER>` env vars — so this function
/// normally just reads them. The Rust code carries no model knowledge;
/// updating model families only requires a Nix change.
///
/// Resolution order (first match wins):
/// 1. `HIVE_CONTEXT_WINDOW_TOKENS_<KEY>` — key (lowercased) is a
///    substring of the active model name. Populated by the Nix default
///    map for all known families; add/override in `agent.nix`.
/// 2. `HIVE_CONTEXT_WINDOW_TOKENS` — single global override (any model).
/// 3. Hard fallback: `200_000` (conservative; only hit outside NixOS).
#[must_use]
pub fn context_window_tokens(model: &str) -> u64 {
    let m = model.to_ascii_lowercase();
    // Per-model env vars set by `hyperhive.contextWindowTokens` in Nix.
    for (key, val) in std::env::vars() {
        if let Some(suffix) = key.strip_prefix("HIVE_CONTEXT_WINDOW_TOKENS_")
            && !suffix.is_empty()
            && m.contains(&suffix.to_ascii_lowercase())
            && let Ok(v) = val.trim().parse::<u64>()
            && v > 0
        {
            return v;
        }
    }
    // Global override (single value, any model).
    if let Ok(s) = std::env::var("HIVE_CONTEXT_WINDOW_TOKENS")
        && let Ok(v) = s.trim().parse::<u64>()
        && v > 0
    {
        return v;
    }
    // Hard fallback for dev/test outside NixOS where env vars aren't set.
    200_000
}

#[cfg(test)]
mod tests {
    use super::{DEFAULT_EFFORT, EFFORT_LEVELS, is_valid_effort};

    #[test]
    fn effort_validation_accepts_only_known_levels() {
        for level in EFFORT_LEVELS {
            assert!(is_valid_effort(level), "{level} should be valid");
        }
        // Out-of-set, empty, and wrong-case inputs are rejected so a bad
        // picker POST never reaches `claude --effort`.
        for bad in ["lowest", "", "MEDIUM", "ultra", "high "] {
            assert!(!is_valid_effort(bad), "{bad:?} should be rejected");
        }
    }

    #[test]
    fn compiled_default_effort_is_selectable() {
        // The fallback must itself be a valid level, and match the value
        // baked into prompts/claude-settings.json.
        assert!(EFFORT_LEVELS.contains(&DEFAULT_EFFORT));
        assert_eq!(DEFAULT_EFFORT, "medium");
    }
}