use crate::router::McpTool;
use crate::state::MemoryState;
use crate::tools::GetActiveWorktreeContextTool;
use async_trait::async_trait;
use serde_json::{Value, json};
use std::env;
use std::sync::Arc;

pub struct GetActiveWorktreeContextHandler;

#[async_trait]
impl McpTool for GetActiveWorktreeContextHandler {
    fn name(&self) -> &'static str {
        "get_active_worktree_context"
    }

    fn schema(&self) -> Value {
        crate::mcp::tool_def::<GetActiveWorktreeContextTool>(
            "get_active_worktree_context",
            "Get the active worktree context, including branch name, modified files, and a truncated git diff.",
        )
    }

    async fn execute(
        &self,
        _args: Value,
        _state: Arc<MemoryState>,
    ) -> crate::error::Result<String> {
        let result =
            tokio::task::spawn_blocking(move || -> crate::error::Result<serde_json::Value> {
                let cwd = env::current_dir().map_err(|e| e.to_string())?;
                let repo = git2::Repository::discover(&cwd).map_err(|e| {
                    crate::error::AppError::Internal(format!("Not in a git repository: {}", e))
                })?;

                let mut branch_name = String::new();
                if let Ok(head) = repo.head()
                    && let Some(name) = head.shorthand()
                {
                    branch_name = name.to_string();
                }

                let mut opts = git2::DiffOptions::new();
                let mut diff = None;

                // Try to diff against HEAD
                if let Ok(tree) = repo.head().and_then(|h| h.peel_to_tree()) {
                    diff = repo
                        .diff_tree_to_workdir_with_index(Some(&tree), Some(&mut opts))
                        .ok();
                }

                let mut files = Vec::new();
                let mut diff_output = String::new();

                if let Some(diff) = diff {
                    let _ = diff.print(git2::DiffFormat::Patch, |_delta, _hunk, line| {
                        match line.origin() {
                            '+' | '-' | ' ' => diff_output.push(line.origin()),
                            _ => {}
                        }
                        let content = std::str::from_utf8(line.content()).unwrap_or("");
                        diff_output.push_str(content);
                        true
                    });

                    for delta in diff.deltas() {
                        if let Some(path) = delta.new_file().path() {
                            files.push(path.to_string_lossy().into_owned());
                        }
                    }
                }

                // Truncate diff output if it's too large to save tokens
                if diff_output.len() > 10000 {
                    let valid_boundary = diff_output.floor_char_boundary(10000);
                    diff_output.truncate(valid_boundary);
                    diff_output.push_str("\n... [Diff truncated due to size]");
                }

                Ok(json!({
                    "branch": branch_name,
                    "modified_files": files,
                    "diff": diff_output
                }))
            })
            .await
            .map_err(|e| crate::error::AppError::Internal(format!("Task panic: {}", e)))??;

        Ok::<String, crate::error::AppError>(serde_json::to_string_pretty(&result)?)
    }
}

pub struct QueryGitDiffsHandler;

#[async_trait]
impl McpTool for QueryGitDiffsHandler {
    fn name(&self) -> &'static str {
        "query_git_diffs"
    }

    fn schema(&self) -> Value {
        crate::mcp::tool_def::<crate::tools::QueryGitDiffsTool>(
            "query_git_diffs",
            "Query recent git commit history, diffs, and change ledger entries.",
        )
    }

    async fn execute(&self, args: Value, state: Arc<MemoryState>) -> crate::error::Result<String> {
        let req: crate::tools::QueryGitDiffsTool =
            serde_json::from_value(args).map_err(|e| e.to_string())?;
        let limit = req.limit.unwrap_or(5);
        let q = req.query.to_lowercase();

        let mut matches = Vec::new();

        state.code.ledger.read_with(|ledger| {
            for change in ledger {
                if change.file_path.to_lowercase().contains(&q)
                    || change.description.to_lowercase().contains(&q)
                    || change.git_commit.as_ref().is_some_and(|c| c.contains(&q))
                {
                    matches.push(json!({
                        "file_path": change.file_path,
                        "description": change.description,
                        "commit": change.git_commit,
                        "branch": change.git_branch,
                        "timestamp": change.timestamp,
                    }));
                    if matches.len() >= limit {
                        break;
                    }
                }
            }
        });

        if matches.len() < limit {
            let remaining = limit - matches.len();
            let git_matches = tokio::task::spawn_blocking(move || {
                let mut results = Vec::new();
                let cwd = env::current_dir().unwrap_or_default();
                if let Ok(repo) = git2::Repository::discover(&cwd)
                    && let Ok(mut revwalk) = repo.revwalk() {
                        let _ = revwalk.push_head();
                        let mut count = 0;
                        for oid in revwalk.flatten() {
                            if count >= remaining {
                                break;
                            }
                            if let Ok(commit) = repo.find_commit(oid) {
                                let summary = commit.summary().unwrap_or("");
                                if summary.to_lowercase().contains(&q) {
                                    count += 1;
                                    results.push(json!({
                                        "commit_id": oid.to_string(),
                                        "author": commit.author().name().unwrap_or("unknown"),
                                        "message": summary,
                                        "timestamp": commit.time().seconds(),
                                    }));
                                }
                            }
                        }
                    }
                results
            })
            .await
            .unwrap_or_default();
            matches.extend(git_matches);
        }

        Ok(serde_json::to_string_pretty(&matches)?)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;
    use std::sync::Arc;
    use tempfile::tempdir;

    #[tokio::test]
    async fn test_get_active_worktree_context() {
        let dir = tempdir().unwrap();
        let state = Arc::new(MemoryState::new(dir.path().to_str().unwrap()));
        let handler = GetActiveWorktreeContextHandler;

        let result = handler
            .execute(json!({}), state)
            .await
            .map_err(|e| format!("Failed to get worktree context: {}", e))
            .unwrap();

        let parsed: serde_json::Value = serde_json::from_str(&result).unwrap();
        assert!(parsed.get("branch").is_some());
        assert!(parsed.get("modified_files").is_some());
        assert!(parsed.get("diff").is_some());
    }

    #[tokio::test]
    async fn test_get_active_worktree_context_empty_git_repo() {
        let dir = tempfile::tempdir().unwrap();
        let state = Arc::new(MemoryState::new(dir.path().to_str().unwrap()));

        let handler = GetActiveWorktreeContextHandler;

        let result = handler
            .execute(serde_json::json!({}), state)
            .await
            .map_err(|e| format!("Failed to get worktree context: {}", e))
            .unwrap();

        let parsed: serde_json::Value = serde_json::from_str(&result).unwrap();
        assert!(parsed.get("branch").is_some() || parsed.is_object());
    }
}