brazen 0.0.4

//! Leaf JSON accessors shared by every protocol decode/encode (protocol-dedup
//! spec, D1). Pure over `&Value`/`&[u8]` with zero wire knowledge — the canonical
//! "JSON access" mechanics, the single home for what was copied per provider. The
//! synthesized-stream mechanics (`next_index`/`open_text`/`drain`) live in `synth`.

use serde_json::{Map, Value};

use crate::canonical::{CanonicalError, ErrorKind, Model};
use crate::protocol::{ModelKeys, WireRequest};

/// Project a models-list body onto the canonical ordered `Vec<Model>` (model-discovery
/// §3.1), the single home every `decode_models` shares. The dialects coincide on the
/// shape — a top-level `array_key` array of objects each carrying the wire id at
/// `id_key` — so they differ only as DATA ([`ModelKeys`]): the id/array keys, Google's
/// `strip` of a leading `models/`, and the OPTIONAL metadata key paths (each `""` when
/// unserved, so the field stays `None`, never fabricated — §3). ORDER-PRESERVING: the
/// `Vec` index IS the provider's suggested order (§4 reads it). A body that is not the
/// expected `{array_key:[…]}` shape is a `Provider{502}` error — the list-models GET
/// drained a 2xx, so an unparseable list is an upstream contract violation, never a
/// silent empty list (§3.1). `default` is `false`: no dialect flags one today (§3).
pub(crate) fn decode_models(data: &[u8], keys: &ModelKeys) -> Result<Vec<Model>, CanonicalError> {
    let v: Value = serde_json::from_slice(data).map_err(|e| models_error(&e.to_string()))?;
    let entries = v[keys.array_key]
        .as_array()
        .ok_or_else(|| models_error(&format!("models body has no `{}` array", keys.array_key)))?;
    Ok(entries
        .iter()
        .filter_map(|e| {
            let id = e[keys.id_key].as_str()?;
            Some(Model {
                id: id.strip_prefix(keys.strip).unwrap_or(id).to_owned(),
                default: false,
                context_window: opt_u32(e, keys.context_key),
                max_output_tokens: opt_u32(e, keys.max_output_key),
                display_name: opt_str(e, keys.display_name_key),
            })
        })
        .collect())
}

/// An optional `u32` metadata field (model-discovery §3): the value at `key` when it is
/// a non-negative integer that fits `u32`, else `None` — absent, non-numeric, or out of
/// range, and a `""` key (an unserved fact) is always absent ⇒ `None`. Distinct from
/// `u32_at`, which fabricates `0`: a provider that does not report the limit leaves it
/// UNKNOWN, not zero (the Usage zero-vs-unknown principle, AGENTS.md).
fn opt_u32(v: &Value, key: &str) -> Option<u32> {
    v[key].as_u64().and_then(|n| u32::try_from(n).ok())
}

/// An optional string metadata field (model-discovery §3): the string at `key`, else
/// `None` — absent, non-string, or a `""` key. Distinct from `text_of`, which fabricates
/// `""`: an unserved label stays `None`, never an empty string.
fn opt_str(v: &Value, key: &str) -> Option<String> {
    v[key].as_str().map(str::to_owned)
}

/// A malformed/unexpected models-list body → `Provider{502}` (model-discovery §3.1):
/// the list-models GET drained a 2xx, so a body we cannot project is the upstream
/// returning an invalid response (Bad Gateway), retryable like any 5xx — distinct
/// from `parse`'s mid-stream `Transport`, which has no governing status.
fn models_error(detail: &str) -> CanonicalError {
    CanonicalError {
        kind: ErrorKind::Provider { status: 502 },
        message: format!("malformed models list: {detail}"),
        provider_detail: None,
        retry_after_seconds: None,
    }
}

/// Read the token count from a 2xx count-endpoint body (architecture §5.10.1, bl-24e5):
/// the number at the response `key` a [`CountRequest`](crate::protocol::CountRequest)
/// supplies (`input_tokens` Anthropic, `totalTokens` Google). The `--count-tokens`
/// round-trip drained a 2xx, so a body that is not JSON or carries no numeric `key` is a
/// `Provider{502}` — an upstream contract violation, the count analog of a malformed
/// models list (§3.1) — never a silent zero (fabricating a count is the lie the op
/// exists to avoid).
pub(crate) fn count_from_body(data: &[u8], key: &str) -> Result<u32, CanonicalError> {
    let v: Value = serde_json::from_slice(data).map_err(|e| count_error(&e.to_string()))?;
    v[key]
        .as_u64()
        .map(|n| n as u32)
        .ok_or_else(|| count_error(&format!("count body has no `{key}` number")))
}

/// A malformed/unexpected count body → `Provider{502}` (bl-24e5): the count GET drained
/// a 2xx, so a body we cannot read is the upstream returning an invalid response — the
/// sibling of [`models_error`], retryable like any 5xx.
fn count_error(detail: &str) -> CanonicalError {
    CanonicalError {
        kind: ErrorKind::Provider { status: 502 },
        message: format!("malformed token count: {detail}"),
        provider_detail: None,
        retry_after_seconds: None,
    }
}

/// Parse a frame's bytes as JSON; a malformed body surfaces as a `Transport`
/// error, never a panic (the wire never crashes us).
pub(crate) fn parse(data: &[u8]) -> Result<Value, CanonicalError> {
    serde_json::from_slice(data).map_err(|e| CanonicalError {
        kind: ErrorKind::Transport,
        message: e.to_string(),
        provider_detail: None,
        retry_after_seconds: None,
    })
}

/// A string field, or `""` when absent/non-string (the wire never panics us).
pub(crate) fn text_of(v: &Value, key: &str) -> String {
    v[key].as_str().unwrap_or_default().to_owned()
}

/// A non-empty string at `v`, else `None` — collapses null / absent / `""` so a
/// role-only chunk and a stray empty fragment open no block.
pub(crate) fn nonempty(v: &Value) -> Option<&str> {
    v.as_str().filter(|s| !s.is_empty())
}

/// A `u32` wire index field, or `0` when absent — the wire never panics us.
pub(crate) fn u32_at(v: &Value, key: &str) -> u32 {
    v[key].as_u64().unwrap_or(0) as u32
}

/// A `Value` → its JSON-encoded **string** (for a tool-call `arguments` slot, or a
/// single `JsonDelta` fragment): re-serialization of a `serde_json::Value` is
/// infallible.
pub(crate) fn to_json_string(v: &Value) -> String {
    #[allow(clippy::expect_used)]
    serde_json::to_string(v).expect("a serde_json::Value re-serializes infallibly")
}

/// The byte-identical encoder tail every `encode` shares (protocol-dedup spec, D1):
/// serialize the assembled `body` (our own owned `Map<String,Value>` serializes
/// infallibly — the lone `expect_used` for the whole encoder layer lives here, not
/// once per dialect) and wrap it in a `WireRequest` at the caller-built `url`. Neither
/// content-type NOR the row's `beta_headers` are stamped here: both are row/dialect
/// facts the wire needs on BOTH the encoded and the `--raw` paths, so their single
/// home is `serve` (`Protocol::content_type()` and `ctx.beta_headers`, stamped once
/// for both) — not once per `encode`, which `--raw` would skip (bl-3e2f). The only
/// per-dialect variation is how `url` is computed, so the caller builds it and hands
/// it in.
pub(crate) fn finish_body(body: Map<String, Value>, url: String) -> WireRequest {
    #[allow(clippy::expect_used)]
    let bytes = serde_json::to_vec(&body).expect("request body is infallibly serializable");
    WireRequest::new(url, bytes)
}

/// The ONE whole-body non-2xx HTTP error projection, shared by every protocol's
/// decode (bl-5fe6). The HTTP status is the authoritative fact — `kind` derives
/// from it via the single `ErrorKind::from_http_status` table — and the **RAW
/// response body rides `provider_detail` VERBATIM** so a provider error is never
/// undiagnosable, whatever envelope shape it took. We deliberately do NOT assume a
/// uniform `{"error":…}` schema: OpenAI's codex backend returns `{"detail":…}`,
/// Ollama a bare `{"error":"…"}` string, a proxy plain HTML — the bytes that
/// actually arrived are what diagnose the failure, so they are what we carry.
///
/// A JSON body rides as the parsed `Value`; a non-JSON body (proxy HTML, plain
/// text) rides as a `Value::String` of its bytes; an empty body degrades to
/// `None`. `message` is a best-effort human summary pulled from a known field
/// (`error.message`, a bare `error` string, or `detail`), else the body itself —
/// never empty when a body exists, so text mode (which shows only `message`) is
/// diagnosable too. The body is a RESPONSE — it carries no request creds, so there
/// is no secret to redact here.
pub(crate) fn http_error(data: &[u8], status: u16) -> CanonicalError {
    let kind = ErrorKind::from_http_status(status);
    let (message, provider_detail) = match serde_json::from_slice::<Value>(data) {
        Ok(body) => (error_message(&body), Some(body)),
        Err(_) => {
            // Non-JSON: surface the raw bytes verbatim rather than discard them.
            let raw = String::from_utf8_lossy(data).trim().to_owned();
            if raw.is_empty() {
                (String::new(), None)
            } else {
                (raw.clone(), Some(Value::String(raw)))
            }
        }
    };
    CanonicalError {
        kind,
        message,
        provider_detail,
        retry_after_seconds: None,
    }
}

/// Best-effort human message from a parsed error body: a nested `error.message`, a
/// bare `error` string (Ollama), or a `detail` string (OpenAI codex) — else the
/// whole body re-serialized, so the message is never empty when a body parsed.
fn error_message(body: &Value) -> String {
    body["error"]["message"]
        .as_str()
        .or_else(|| body["error"].as_str())
        .or_else(|| body["detail"].as_str())
        .map(str::to_owned)
        .unwrap_or_else(|| to_json_string(body))
}