//! Tool dispatch — plan/execute helpers for the per-turn tool batch.
//!
//! Extracted from `core/engine.rs` (P1.3). The high-level ordering still
//! lives in `Engine::handle_deepseek_turn`; this module owns:
//!
//! * Streaming-buffer parsing into a finalized `serde_json::Value` tool input
//!   (`final_tool_input`, `parse_tool_input`, fenced/JSON segment helpers).
//! * The `multi_tool_use.parallel` payload parser.
//! * Policy predicates the turn loop consults — when a batch can run in
//!   parallel, when an `update_plan` step should stop the turn, when a Plan
//!   prompt should force a plan-first hop, and the small set of read-only
//!   MCP tools that are safe to run in parallel.
//! * The tool execution plan/outcome types the batch driver passes around.
//!
//! All items are `pub(super)`-only: the public engine surface (Op/Event,
//! `EngineHandle`, `spawn_engine`) stays in `engine/mod.rs`.

use serde_json::json;

use crate::models::ToolCaller;
use crate::tools::spec::{ToolError, ToolResult};
use crate::tui::app::AppMode;

use super::ToolUseState;

// === Types ============================================================

#[allow(dead_code)] // `index` mirrors batch order for diagnostic ergonomics.
pub(super) struct ToolExecOutcome {
    pub(super) index: usize,
    pub(super) id: String,
    pub(super) name: String,
    pub(super) input: serde_json::Value,
    pub(super) started_at: std::time::Instant,
    pub(super) result: Result<ToolResult, ToolError>,
}

#[derive(Debug, Clone)]
pub(super) struct ToolExecutionPlan {
    pub(super) index: usize,
    pub(super) id: String,
    pub(super) name: String,
    pub(super) input: serde_json::Value,
    pub(super) caller: Option<ToolCaller>,
    pub(super) interactive: bool,
    pub(super) approval_required: bool,
    pub(super) approval_description: String,
    pub(super) supports_parallel: bool,
    pub(super) read_only: bool,
    pub(super) blocked_error: Option<ToolError>,
}

#[derive(Debug, serde::Serialize)]
pub(super) struct ParallelToolResultEntry {
    pub(super) tool_name: String,
    pub(super) success: bool,
    pub(super) content: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub(super) error: Option<String>,
}

#[derive(Debug, serde::Serialize)]
pub(super) struct ParallelToolResult {
    pub(super) results: Vec<ParallelToolResultEntry>,
}

// Hold the lock guard for the duration of a tool execution.
// The inner guards are held for RAII purposes (dropped when the guard is dropped).
pub(super) enum ToolExecGuard<'a> {
    Read(#[allow(dead_code)] tokio::sync::RwLockReadGuard<'a, ()>),
    Write(#[allow(dead_code)] tokio::sync::RwLockWriteGuard<'a, ()>),
}

// === Streaming-buffer parsing =========================================

/// Promote a streaming `ToolUseState` to a finalized JSON input.
///
/// Order of preference:
///
///   1. `input_buffer` (the raw streamed delta concatenation) — parsed as
///      JSON. This is the most authoritative because it's what the model
///      actually emitted.
///   2. `input` (the per-delta best-effort parse mirror) — used when the
///      buffer is empty (pre-streaming tool calls take this path).
///   3. `input_buffer` non-empty but unparseable → fall back to `input`
///      (the per-delta parser has already mirrored the most recent valid
///      partial parse into `tool_state.input`).
pub(super) fn final_tool_input(state: &ToolUseState) -> serde_json::Value {
    if !state.input_buffer.trim().is_empty()
        && let Some(parsed) = parse_tool_input(&state.input_buffer)
    {
        return parsed;
    }
    state.input.clone()
}

pub(super) fn parse_tool_input(buffer: &str) -> Option<serde_json::Value> {
    let trimmed = buffer.trim();
    if trimmed.is_empty() {
        return None;
    }
    if let Ok(value) = serde_json::from_str::<serde_json::Value>(trimmed) {
        return Some(value);
    }
    if let Some(stripped) = strip_code_fences(trimmed)
        && let Ok(value) = serde_json::from_str::<serde_json::Value>(&stripped)
    {
        return Some(value);
    }
    if let Ok(serde_json::Value::String(inner)) = serde_json::from_str::<serde_json::Value>(trimmed)
        && let Ok(value) = serde_json::from_str::<serde_json::Value>(&inner)
    {
        return Some(value);
    }
    extract_json_segment(trimmed)
        .and_then(|segment| serde_json::from_str::<serde_json::Value>(&segment).ok())
}

fn strip_code_fences(text: &str) -> Option<String> {
    if !text.contains("```") {
        return None;
    }
    let mut lines = Vec::new();
    for line in text.lines() {
        if line.trim_start().starts_with("```") {
            continue;
        }
        lines.push(line);
    }
    let stripped = lines.join("\n");
    let stripped = stripped.trim();
    if stripped.is_empty() {
        None
    } else {
        Some(stripped.to_string())
    }
}

fn extract_json_segment(text: &str) -> Option<String> {
    extract_balanced_segment(text, '{', '}').or_else(|| extract_balanced_segment(text, '[', ']'))
}

fn extract_balanced_segment(text: &str, open: char, close: char) -> Option<String> {
    let start = text.find(open)?;
    let mut depth = 0i32;
    let mut end = None;
    for (offset, ch) in text[start..].char_indices() {
        if ch == open {
            depth += 1;
        } else if ch == close {
            depth -= 1;
            if depth == 0 {
                end = Some(start + offset + ch.len_utf8());
                break;
            }
        }
    }
    end.map(|end_idx| text[start..end_idx].to_string())
}

fn normalize_parallel_tool_name(raw: &str) -> String {
    let mut name = raw.trim();
    for prefix in ["functions.", "tools.", "tool."] {
        if let Some(stripped) = name.strip_prefix(prefix) {
            name = stripped;
            break;
        }
    }
    name.to_string()
}

pub(super) fn parse_parallel_tool_calls(
    input: &serde_json::Value,
) -> Result<Vec<(String, serde_json::Value)>, ToolError> {
    let tool_uses = input
        .get("tool_uses")
        .and_then(|v| v.as_array())
        .ok_or_else(|| ToolError::missing_field("tool_uses"))?;
    if tool_uses.is_empty() {
        return Err(ToolError::invalid_input(
            "multi_tool_use.parallel requires at least one tool call",
        ));
    }

    let mut calls = Vec::with_capacity(tool_uses.len());
    for item in tool_uses {
        let name = item
            .get("recipient_name")
            .or_else(|| item.get("tool_name"))
            .or_else(|| item.get("name"))
            .or_else(|| item.get("tool"))
            .and_then(|v| v.as_str())
            .ok_or_else(|| ToolError::missing_field("recipient_name"))?;
        let params = item
            .get("parameters")
            .or_else(|| item.get("input"))
            .or_else(|| item.get("args"))
            .or_else(|| item.get("arguments"))
            .cloned()
            .unwrap_or_else(|| json!({}));
        calls.push((normalize_parallel_tool_name(name), params));
    }

    Ok(calls)
}

// === Dispatch policy ==================================================

pub(super) fn should_parallelize_tool_batch(plans: &[ToolExecutionPlan]) -> bool {
    !plans.is_empty()
        && plans.iter().all(|plan| {
            plan.read_only && plan.supports_parallel && !plan.approval_required && !plan.interactive
        })
}

pub(super) fn should_stop_after_plan_tool(
    mode: AppMode,
    tool_name: &str,
    result: &Result<ToolResult, ToolError>,
) -> bool {
    mode == AppMode::Plan && tool_name == "update_plan" && result.is_ok()
}

pub(super) fn should_force_update_plan_first(mode: AppMode, content: &str) -> bool {
    if mode != AppMode::Plan {
        return false;
    }

    let lower = content.to_ascii_lowercase();
    let asks_for_direct_plan = [
        "quick plan",
        "short plan",
        "simple plan",
        "3-step plan",
        "3 step plan",
        "three-step plan",
        "three step plan",
        "high-level plan",
        "high level plan",
        "give me a plan",
        "make a plan",
        "outline a plan",
        "draft a plan",
    ]
    .iter()
    .any(|needle| lower.contains(needle));

    if !asks_for_direct_plan {
        return false;
    }

    let asks_for_repo_exploration = [
        "inspect the repo",
        "inspect the code",
        "explore the repo",
        "search the repo",
        "read the code",
        "review the code",
        "analyze the code",
        "investigate",
        "look through",
        "understand the current",
        "ground it in the codebase",
        "based on the codebase",
    ]
    .iter()
    .any(|needle| lower.contains(needle));

    !asks_for_repo_exploration
}

pub(super) fn mcp_tool_is_parallel_safe(name: &str) -> bool {
    matches!(
        name,
        "list_mcp_resources"
            | "list_mcp_resource_templates"
            | "mcp_read_resource"
            | "read_mcp_resource"
            | "mcp_get_prompt"
    )
}

pub(super) fn mcp_tool_is_read_only(name: &str) -> bool {
    matches!(
        name,
        "list_mcp_resources"
            | "list_mcp_resource_templates"
            | "mcp_read_resource"
            | "read_mcp_resource"
            | "mcp_get_prompt"
    )
}

pub(super) fn mcp_tool_approval_description(name: &str) -> String {
    if mcp_tool_is_read_only(name) {
        format!("Read-only MCP tool '{name}'")
    } else {
        format!("MCP tool '{name}' may have side effects")
    }
}
