codex-rs/core/src/models.rs

use base64::Engine;
use serde::ser::Serializer;
use serde::Deserialize;
use serde::Serialize;

use crate::protocol::InputItem;

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ResponseInputItem {
    Message {
        role: String,
        content: Vec<ContentItem>,
    },
    FunctionCallOutput {
        call_id: String,
        output: FunctionCallOutputPayload,
    },
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ContentItem {
    InputText { text: String },
    InputImage { image_url: String },
    OutputText { text: String },
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ResponseItem {
    Message {
        role: String,
        content: Vec<ContentItem>,
    },
    FunctionCall {
        name: String,
        // The Responses API returns the function call arguments as a *string* that contains
        // JSON, not as an already‑parsed object. We keep it as a raw string here and let
        // Session::handle_function_call parse it into a Value. This exactly matches the
        // Chat Completions + Responses API behavior.
        arguments: String,
        call_id: String,
    },
    // NOTE: The input schema for `function_call_output` objects that clients send to the
    // OpenAI /v1/responses endpoint is NOT the same shape as the objects the server returns on the
    // SSE stream. When *sending* we must wrap the string output inside an object that includes a
    // required `success` boolean. The upstream TypeScript CLI does this implicitly. To ensure we
    // serialize exactly the expected shape we introduce a dedicated payload struct and flatten it
    // here.
    FunctionCallOutput {
        call_id: String,
        output: FunctionCallOutputPayload,
    },
    #[serde(other)]
    Other,
}

impl From<ResponseInputItem> for ResponseItem {
    fn from(item: ResponseInputItem) -> Self {
        match item {
            ResponseInputItem::Message { role, content } => Self::Message { role, content },
            ResponseInputItem::FunctionCallOutput { call_id, output } => {
                Self::FunctionCallOutput { call_id, output }
            }
        }
    }
}

impl From<Vec<InputItem>> for ResponseInputItem {
    fn from(items: Vec<InputItem>) -> Self {
        Self::Message {
            role: "user".to_string(),
            content: items
                .into_iter()
                .filter_map(|c| match c {
                    InputItem::Text { text } => Some(ContentItem::InputText { text }),
                    InputItem::Image { image_url } => Some(ContentItem::InputImage { image_url }),
                    InputItem::LocalImage { path } => match std::fs::read(&path) {
                        Ok(bytes) => {
                            let mime = mime_guess::from_path(&path)
                                .first()
                                .map(|m| m.essence_str().to_owned())
                                .unwrap_or_else(|| "application/octet-stream".to_string());
                            let encoded = base64::engine::general_purpose::STANDARD.encode(bytes);
                            Some(ContentItem::InputImage {
                                image_url: format!("data:{};base64,{}", mime, encoded),
                            })
                        }
                        Err(err) => {
                            tracing::warn!(
                                "Skipping image {} – could not read file: {}",
                                path.display(),
                                err
                            );
                            None
                        }
                    },
                })
                .collect::<Vec<ContentItem>>(),
        }
    }
}

#[expect(dead_code)]
#[derive(Deserialize, Debug, Clone)]
pub struct FunctionCallOutputPayload {
    pub content: String,
    pub success: Option<bool>,
}

// The Responses API expects two *different* shapes depending on success vs failure:
//   • success → output is a plain string (no nested object)
//   • failure → output is an object { content, success:false }
// The upstream TypeScript CLI implements this by special‑casing the serialize path.
// We replicate that behavior with a manual Serialize impl.

impl Serialize for FunctionCallOutputPayload {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        // The upstream TypeScript CLI always serializes `output` as a *plain string* regardless
        // of whether the function call succeeded or failed. The boolean is purely informational
        // for local bookkeeping and is NOT sent to the OpenAI endpoint. Sending the nested object
        // form `{ content, success:false }` triggers the 400 we are still seeing. Mirror the JS CLI
        // exactly: always emit a bare string.

        serializer.serialize_str(&self.content)
    }
}

// Implement Display so callers can treat the payload like a plain string when logging or doing
// trivial substring checks in tests (existing tests call `.contains()` on the output). Display
// returns the raw `content` field.

impl std::fmt::Display for FunctionCallOutputPayload {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.content)
    }
}

impl std::ops::Deref for FunctionCallOutputPayload {
    type Target = str;
    fn deref(&self) -> &Self::Target {
        &self.content
    }
}

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

    #[test]
    fn serializes_success_as_plain_string() {
        let item = ResponseInputItem::FunctionCallOutput {
            call_id: "call1".into(),
            output: FunctionCallOutputPayload {
                content: "ok".into(),
                success: None,
            },
        };

        let json = serde_json::to_string(&item).unwrap();
        let v: serde_json::Value = serde_json::from_str(&json).unwrap();

        // Success case -> output should be a plain string
        assert_eq!(v.get("output").unwrap().as_str().unwrap(), "ok");
    }

    #[test]
    fn serializes_failure_as_string() {
        let item = ResponseInputItem::FunctionCallOutput {
            call_id: "call1".into(),
            output: FunctionCallOutputPayload {
                content: "bad".into(),
                success: Some(false),
            },
        };

        let json = serde_json::to_string(&item).unwrap();
        let v: serde_json::Value = serde_json::from_str(&json).unwrap();

        assert_eq!(v.get("output").unwrap().as_str().unwrap(), "bad");
    }
}