roder-core 0.3.7

use crate::tool_result_images::{IMAGE_WITHHELD_NOTICE, ToolImages, carries_image};
use roder_api::transcript::TranscriptItem;
use serde_json::Value;
use std::collections::HashSet;

/// Tokens for the notice line (and its newline) that `request_transcript`
/// adds to a tool result whose image it withheld. The stored transcript the
/// estimate reads does not contain it.
const WITHHELD_NOTICE_TOKENS: u32 = (IMAGE_WITHHELD_NOTICE.len() + 1).div_ceil(4) as u32;

/// Estimates opaque provider state and image input separately from canonical
/// text. These are conservative estimates, never billing or payload-byte claims.
/// A tool-result image is charged only when the engine receives it; otherwise
/// the notice that replaces it is.
pub(crate) fn extra_prompt_tokens(items: &[TranscriptItem], images: ToolImages) -> u32 {
    let mut seen = HashSet::new();
    let mut tokens = 0u32;
    for item in items {
        match item {
            TranscriptItem::UserMessage(message) => {
                tokens = tokens.saturating_add((message.images.len() as u32).saturating_mul(1_600));
            }
            TranscriptItem::ToolResult(result) if carries_image(result) => {
                tokens = tokens.saturating_add(match images {
                    ToolImages::Forwarded => 1_600,
                    ToolImages::Withheld => WITHHELD_NOTICE_TOKENS,
                });
            }
            TranscriptItem::ProviderMetadata(metadata) => {
                if let Some(window) = metadata.get("compacted_input") {
                    tokens = tokens.saturating_add(value_tokens(window));
                    continue;
                }
                for raw in metadata
                    .get("output")
                    .and_then(Value::as_array)
                    .into_iter()
                    .flatten()
                {
                    let key = raw
                        .get("id")
                        .and_then(Value::as_str)
                        .map(String::from)
                        .unwrap_or_else(|| raw.to_string());
                    if !seen.insert(key) {
                        continue;
                    }
                    if matches!(
                        raw["type"].as_str(),
                        Some("reasoning" | "compaction" | "compaction_summary")
                    ) && let Some(opaque) = raw.get("encrypted_content").and_then(Value::as_str)
                    {
                        tokens = tokens.saturating_add(
                            opaque.len().div_ceil(4).try_into().unwrap_or(u32::MAX),
                        );
                    }
                }
            }
            _ => {}
        }
    }
    tokens
}

pub(crate) fn value_tokens(value: &Value) -> u32 {
    match value {
        Value::String(text) => text.len().div_ceil(4).try_into().unwrap_or(u32::MAX),
        Value::Array(items) => items
            .iter()
            .fold(0u32, |sum, item| sum.saturating_add(value_tokens(item))),
        Value::Object(fields) => fields.iter().fold(0u32, |sum, (key, value)| {
            sum.saturating_add(if key == "image_url" {
                1_600
            } else {
                value_tokens(value)
            })
        }),
        _ => 0,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;
    #[test]
    fn counts_encrypted_state_once_and_excludes_transport_telemetry() {
        let raw = json!({"id":"reason1","type":"reasoning","encrypted_content":"x".repeat(4_000)});
        assert_eq!(
            extra_prompt_tokens(
                &[
                    TranscriptItem::ProviderMetadata(json!({"output":[raw]})),
                    TranscriptItem::ProviderMetadata(json!({"output":[raw]})),
                    TranscriptItem::ProviderMetadata(json!({"diagnostics":"x".repeat(8_000)}))
                ],
                ToolImages::Forwarded
            ),
            1_000
        );
    }
    fn tool_result(id: &str, payload: Option<Value>, is_error: bool) -> TranscriptItem {
        TranscriptItem::ToolResult(roder_api::transcript::ToolResultRecord {
            id: id.into(),
            name: Some("browser_use_click".into()),
            result: "clicked. Screenshot attached.".into(),
            display_payload: payload,
            is_error,
        })
    }
    #[test]
    fn tool_result_images_are_charged_only_for_engines_that_receive_them() {
        let shot = || Some(json!({"__view_image": {"image_url": "data:image/png;base64,YWJj"}}));
        let items = vec![
            tool_result("ok", shot(), false),
            tool_result("failed", shot(), true),
            tool_result("no-image", Some(json!({"path": "a"})), false),
            TranscriptItem::UserMessage(roder_api::transcript::UserMessage::with_images(
                "look",
                vec![roder_api::transcript::InputImage {
                    image_url: "data:image/png;base64,YWJj".into(),
                }],
            )),
        ];
        assert_eq!(
            extra_prompt_tokens(&items, ToolImages::Forwarded),
            3 * 1_600
        );
        // The user's own image is still sent; only the tool-result images go,
        // and each leaves the notice that stands in for it.
        let notice_tokens = (IMAGE_WITHHELD_NOTICE.len() as u32 + 1).div_ceil(4);
        assert_eq!(
            extra_prompt_tokens(&items, ToolImages::Withheld),
            1_600 + 2 * notice_tokens
        );
    }
    fn result_text_len(item: &TranscriptItem) -> usize {
        match item {
            TranscriptItem::ToolResult(result) => result.result.len(),
            other => panic!("not a tool result: {other:?}"),
        }
    }
    #[test]
    fn withheld_images_are_charged_the_notice_the_engine_receives_instead() {
        let items = vec![tool_result(
            "ok",
            Some(json!({"__view_image": {"image_url": "data:image/png;base64,YWJj"}})),
            false,
        )];
        // The compaction estimate counts the stored text; the engine is sent
        // that text plus whatever `request_transcript` adds to it.
        let sent = crate::tool_result_images::request_transcript(&items, ToolImages::Withheld);
        let added_chars = result_text_len(&sent[0]) - result_text_len(&items[0]);
        assert!(added_chars > 0, "a withheld image leaves a notice");
        assert_eq!(
            extra_prompt_tokens(&items, ToolImages::Withheld),
            added_chars.div_ceil(4) as u32
        );
    }
    #[test]
    fn images_count_as_image_estimates_not_base64_text_tokens() {
        assert_eq!(
            value_tokens(
                &json!({"type":"input_image","image_url":"data:image/png;base64,".to_string()+&"A".repeat(80_000)})
            ),
            1_603
        );
    }
}