//! Layered configuration: defaults, the user file, the repository file.

use super::*;

/// Effective settings: defaults, then the user file (`~/.config/oxy/config.toml`,
/// spec §19), then the repository file (`.oxy/config`). Both files are
/// `key = "value"` lines. `save` writes only the repository layer.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Config {
    /// Keys set in the repository file (or via `set`), written by `save`.
    repo_layer: BTreeMap<String, String>,
    pub author_name: String,
    pub author_email: String,
    /// The KeyId of the author's identity, once `create_identity` has run.
    pub author_key: Option<KeyId>,
    /// `core.sign`: sign every change at commit (`true`) or leave signing to
    /// push-time seals (`false`, the spec default).
    pub sign_changes: bool,
    pub bookmark: String,
    /// `remote.<name>.url`.
    pub remotes: BTreeMap<String, String>,
    /// `remote.<name>.token`: bearer token for HTTP pushes.
    pub remote_tokens: BTreeMap<String, String>,
    /// `remote.<name>.ca`: PEM file of extra roots to trust for that remote.
    pub remote_cas: BTreeMap<String, String>,
    /// `core.op-retention`: days for which operations keep their states reachable (spec §12.1, §21).
    pub op_retention_days: u64,
    /// `core.gc-grace`: days an unreachable object survives, protecting concurrent writers (spec §21).
    pub gc_grace_days: u64,
    /// `core.checkpoint-interval`: changes between automatic checkpoints (spec §11).
    pub checkpoint_interval: u64,
    /// `filter.max-blob`: blobs larger than this many bytes are fetched lazily (spec §17).
    pub max_blob: Option<u64>,
    /// `filter.paths`: only these subtrees are materialized (spec §17); empty means everything.
    pub sparse_paths: Vec<String>,
    /// `hooks.semantic-deps`: run the semantic-deps hook at commit (spec §20).
    pub semantic_deps: bool,
}

impl Config {
    pub(super) fn default_for_user() -> Config {
        let user = std::env::var("USER").unwrap_or_else(|_| "unknown".into());
        Config {
            repo_layer: BTreeMap::new(),
            author_name: std::env::var("OXY_AUTHOR_NAME").unwrap_or_else(|_| user.clone()),
            author_email: std::env::var("OXY_AUTHOR_EMAIL")
                .unwrap_or_else(|_| format!("{user}@localhost")),
            author_key: None,
            sign_changes: false,
            bookmark: "main".into(),
            remotes: BTreeMap::new(),
            remote_tokens: BTreeMap::new(),
            remote_cas: BTreeMap::new(),
            op_retention_days: 90,
            gc_grace_days: 14,
            checkpoint_interval: 256,
            max_blob: None,
            sparse_paths: Vec::new(),
            semantic_deps: false,
        }
    }

    /// Set a key in the repository layer, as `oxy config` does.
    pub fn set(&mut self, key: &str, value: &str) -> Result<()> {
        self.apply(key, value)?;
        if value.is_empty() {
            self.repo_layer.remove(key);
        } else {
            self.repo_layer.insert(key.to_string(), value.to_string());
        }
        Ok(())
    }

    /// Set a key in the user file without touching any repository.
    pub fn set_user(user_path: &Path, key: &str, value: &str) -> Result<()> {
        Config::default_for_user().apply(key, value)?;
        let mut entries = read_config_file(user_path)?;
        if value.is_empty() {
            entries.remove(key);
        } else {
            entries.insert(key.to_string(), value.to_string());
        }
        if let Some(parent) = user_path.parent() {
            fs::create_dir_all(parent)?;
        }
        write_config_file(user_path, &entries)
    }

    /// Apply a key to the effective values.
    pub(super) fn apply(&mut self, key: &str, value: &str) -> Result<()> {
        match key {
            "author.name" => self.author_name = value.into(),
            "author.email" => self.author_email = value.into(),
            "author.key" => {
                self.author_key = if value.is_empty() {
                    None
                } else {
                    Some(KeyId::from_hex(value).ok_or_else(|| {
                        RepoError::Msg("author.key must be a 64-character hex KeyId".into())
                    })?)
                }
            }
            "core.sign" => {
                self.sign_changes = match value {
                    "change" => true,
                    "seal" => false,
                    _ => return fail("core.sign must be \"change\" or \"seal\""),
                }
            }
            "workspace.bookmark" => self.bookmark = value.into(),
            "core.op-retention" => self.op_retention_days = parse_days(value)?,
            "core.gc-grace" => self.gc_grace_days = parse_days(value)?,
            "filter.max-blob" => {
                self.max_blob = if value.is_empty() {
                    None
                } else {
                    Some(parse_size(value)?)
                }
            }
            "hooks.semantic-deps" => self.semantic_deps = matches!(value, "true" | "1" | "yes"),
            "filter.paths" => {
                self.sparse_paths = value
                    .split(',')
                    .map(|p| {
                        p.trim()
                            .trim_start_matches("./")
                            .trim_matches('/')
                            .to_string()
                    })
                    .filter(|p| !p.is_empty())
                    .collect();
            }
            "core.checkpoint-interval" => {
                self.checkpoint_interval = value
                    .parse()
                    .map_err(|_| RepoError::Msg(format!("expected a number, got {value:?}")))?;
            }
            k if k.starts_with("remote.") => {
                let rest = &k["remote.".len()..];
                let Some((name, field)) = rest.rsplit_once('.') else {
                    return fail(format!("unknown configuration key {key:?}"));
                };
                if name.is_empty() || name.contains('/') {
                    return fail(format!("invalid remote name in {key:?}"));
                }
                let map = match field {
                    "url" => &mut self.remotes,
                    "token" => &mut self.remote_tokens,
                    "ca" => &mut self.remote_cas,
                    _ => return fail(format!("unknown configuration key {key:?}")),
                };
                if value.is_empty() {
                    map.remove(name);
                    if field == "url" {
                        self.remote_tokens.remove(name);
                        self.remote_cas.remove(name);
                    }
                } else {
                    map.insert(name.to_string(), value.into());
                }
            }
            _ => return fail(format!("unknown configuration key {key:?}")),
        }
        Ok(())
    }

    /// Defaults, then the user file if it exists, then the repository file.
    pub(super) fn load(user_path: Option<&Path>, repo_path: &Path) -> Result<Config> {
        let mut c = Config::default_for_user();
        if let Some(u) = user_path {
            for (k, v) in read_config_file(u)? {
                let _ = c.apply(&k, &v);
            }
        }
        for (k, v) in read_config_file(repo_path)? {
            if c.apply(&k, &v).is_ok() {
                c.repo_layer.insert(k, v);
            }
        }
        Ok(c)
    }

    pub(super) fn save(&self, path: &Path) -> Result<()> {
        write_config_file(path, &self.repo_layer)
    }

    /// Keys explicitly set for this repository.
    pub fn repo_layer(&self) -> &BTreeMap<String, String> {
        &self.repo_layer
    }
}

/// A byte count with an optional `K`, `M`, or `G` suffix (binary units).
pub fn parse_size(v: &str) -> Result<u64> {
    let v = v.trim();
    let (num, mult) = match v.chars().last() {
        Some('K' | 'k') => (&v[..v.len() - 1], 1u64 << 10),
        Some('M' | 'm') => (&v[..v.len() - 1], 1u64 << 20),
        Some('G' | 'g') => (&v[..v.len() - 1], 1u64 << 30),
        _ => (v, 1),
    };
    let n: u64 = num
        .trim()
        .parse()
        .map_err(|_| RepoError::Msg(format!("expected a size like 1M, got {v:?}")))?;
    Ok(n * mult)
}

/// A count of days, optionally suffixed `d`.
fn parse_days(v: &str) -> Result<u64> {
    v.trim_end_matches('d')
        .parse()
        .map_err(|_| RepoError::Msg(format!("expected a number of days, got {v:?}")))
}

/// Read `key = "value"` lines; a missing file is empty.
pub fn read_config_file(path: &Path) -> Result<BTreeMap<String, String>> {
    let text = match fs::read_to_string(path) {
        Ok(t) => t,
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(BTreeMap::new()),
        Err(e) => return Err(e.into()),
    };
    let mut out = BTreeMap::new();
    for line in text.lines() {
        let line = line.trim();
        if line.is_empty() || line.starts_with('#') {
            continue;
        }
        let Some((k, v)) = line.split_once('=') else {
            continue;
        };
        out.insert(k.trim().to_string(), v.trim().trim_matches('"').to_string());
    }
    Ok(out)
}

fn write_config_file(path: &Path, entries: &BTreeMap<String, String>) -> Result<()> {
    let text: String = entries
        .iter()
        .map(|(k, v)| format!("{k} = \"{v}\"\n"))
        .collect();
    write_atomic(path, text.as_bytes())
}