use std::time::Duration;

use ai::{
    agent::request::{
        AgentContextChunk, AgentMessage, AgentRequest,
    },
    client::AiClient,
    rag::{
        RagClient, RagConfig, RagDocument,
    },
};
use db::sqlx;
use model::repos::RepoModel;
use uuid::Uuid;

use super::types::SessionContext;
use crate::error::AppError;
use crate::AppService;
const MAX_HISTORY_MESSAGES: u32 = 50;
const MAX_HISTORY_CHARS: usize = 500_000;
const MAX_HISTORY_ESTIMATED_TOKENS: u64 = 64_000;

impl AppService {
    pub(crate) async fn agent_build_request(
        &self,
        ai_client: &AiClient,
        ctx: &SessionContext,
        conversation_id: Option<Uuid>,
        input: String,
        timeout_secs: Option<u64>,
    ) -> Result<AgentRequest, AppError> {
        let mut request = AgentRequest::new(input.clone());
        if let Some(secs) = timeout_secs {
            request = request.with_timeout(Duration::from_secs(secs));
        }
        if let Some(conv_id) = conversation_id {
            let mut all_messages = Vec::new();
            let compacted: Option<String> = sqlx::query_scalar(
                "SELECT compacted_summary FROM agent_conversation WHERE id = $1",
            )
            .bind(conv_id)
            .fetch_optional(self.db.reader())
            .await
            .map_err(|e| AppError::DatabaseError(e.to_string()))?
            .flatten();

            if let Some(summary) = compacted {
                all_messages.push(AgentMessage::User(format!(
                    "[Previous conversation summary]\n{}\n[End of summary — messages below are the most recent verbatim exchanges]",
                    summary
                )));
            }

            let messages = self
                .agent_load_conversation_messages(conv_id)
                .await?;
            all_messages.extend(messages);

            request = request.with_messages(all_messages);
        }
        let kb_context = self
            .agent_load_knowledge_base(ai_client, ctx, &input)
            .await?;
        let (memories_text, _memory_rows) = self.agent_load_memories(ctx.session_id).await?;

        let mut all_context = kb_context;
        if !memories_text.is_empty() {
            all_context.push(AgentContextChunk::new(
                "long_term_memory",
                memories_text,
            ));
        }

        // Inject repo context from @[repo:...] mentions in the input.
        if let Some(workspace_id) = ctx.workspace_id {
            let repo_context = self
                .agent_resolve_mentioned_repos(workspace_id, &input)
                .await
                .unwrap_or_else(|e| {
                    tracing::warn!(error = %e, "failed to resolve mentioned repos");
                    Vec::new()
                });
            all_context.extend(repo_context);
        }

        if !all_context.is_empty() {
            request = request.with_context(all_context);
        }

        Ok(request)
    }
    pub(crate) async fn agent_load_conversation_messages(
        &self,
        conversation_id: Uuid,
    ) -> Result<Vec<AgentMessage>, AppError> {
        let rows: Vec<(String, String)> = sqlx::query_as(
            "SELECT m.role, m.content \
             FROM agent_message m \
             INNER JOIN agent_conversation c ON c.id = m.conversation \
             WHERE m.conversation = $1 \
               AND m.deleted_at IS NULL \
               AND m.status = 'completed' \
               AND c.deleted_at IS NULL \
             ORDER BY m.created_at ASC \
             LIMIT $2",
        )
        .bind(conversation_id)
        .bind(MAX_HISTORY_MESSAGES as i64)
        .fetch_all(self.db.reader())
        .await
        .map_err(|e| AppError::DatabaseError(e.to_string()))?;

        let messages: Vec<AgentMessage> = rows
            .into_iter()
            .map(|(role, content)| match role.as_str() {
                "assistant" => AgentMessage::Assistant(content),
                _ => AgentMessage::User(content),
            })
            .collect();
        let mut total_chars: usize = messages
            .iter()
            .map(|m| match m {
                AgentMessage::User(c) | AgentMessage::Assistant(c) => c.len(),
            })
            .sum();

        let mut result = messages;
        while total_chars > MAX_HISTORY_CHARS && !result.is_empty() {
            let removed = result.remove(0);
            let removed_len = match &removed {
                AgentMessage::User(c) | AgentMessage::Assistant(c) => c.len(),
            };
            total_chars = total_chars.saturating_sub(removed_len);
            tracing::debug!(
                removed_chars = removed_len,
                remaining_chars = total_chars,
                "trimmed oldest message to fit context window"
            );
        }
        let mut estimated_tokens: u64 = result
            .iter()
            .map(|m| match m {
                AgentMessage::User(c) | AgentMessage::Assistant(c) => {
                    ai::agent::helpers::estimate_tokens(c)
                }
            })
            .sum();
        let mut trimmed_for_tokens = 0usize;
        while estimated_tokens > MAX_HISTORY_ESTIMATED_TOKENS && !result.is_empty() {
            let removed = result.remove(0);
            estimated_tokens -= match &removed {
                AgentMessage::User(c) | AgentMessage::Assistant(c) => {
                    ai::agent::helpers::estimate_tokens(c)
                }
            };
            trimmed_for_tokens += 1;
        }
        if trimmed_for_tokens > 0 {
            tracing::info!(
                trimmed = trimmed_for_tokens,
                estimated_tokens = estimated_tokens,
                "trimmed oldest messages to stay within token budget"
            );
        }

        Ok(result)
    }
    pub(crate) async fn agent_load_knowledge_base(
        &self,
        ai_client: &AiClient,
        ctx: &SessionContext,
        query: &str,
    ) -> Result<Vec<AgentContextChunk>, AppError> {
        let knowledge_base_ids: Option<String> = sqlx::query_scalar(
            "SELECT knowledge_base_ids FROM agent_session WHERE id = $1",
        )
        .bind(ctx.session_id)
        .fetch_optional(self.db.reader())
        .await
        .map_err(|e| AppError::DatabaseError(e.to_string()))?
        .flatten();

        let kb_id_str = match knowledge_base_ids {
            Some(ref s) if !s.trim().is_empty() => s.clone(),
            _ => return Ok(Vec::new()),
        };

        let kb_ids: Vec<Uuid> = kb_id_str
            .split(',')
            .filter_map(|s| Uuid::parse_str(s.trim()).ok())
            .collect();

        if kb_ids.is_empty() {
            return Ok(Vec::new());
        }

        let qdrant_url = self
            .config
            .qdrant_url()
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;
        let vector_size = self
            .config
            .get_embed_model_dimensions()
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;

        let rag_config = RagConfig::new(qdrant_url, "agent_knowledge", vector_size)
            .map_err(|e| AppError::InternalServerError(e.to_string()))?
            .with_api_key(
                self.config
                    .qdrant_api_key()
                    .map_err(|e| AppError::InternalServerError(e.to_string()))?,
            );

        let rag = RagClient::connect(ai_client, rag_config)
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;
        let mut all_hits: Vec<AgentContextChunk> = Vec::new();
        for kb_id in &kb_ids {
            let session_key = format!("kb:{kb_id}");
            match rag.search_session(&session_key, query).await {
                Ok(hits) => {
                    for hit in hits {
                        all_hits.push(AgentContextChunk::from(ai::rag::RagSearchHit {
                            id: hit.id,
                            session_id: hit.session_id,
                            score: hit.score,
                            content: hit.content,
                            metadata: hit.metadata,
                        }));
                    }
                }
                Err(e) => {
                    tracing::warn!(
                        kb_id = %kb_id,
                        error = %e,
                        "agent: RAG search failed for knowledge base, skipping"
                    );
                }
            }
        }

        Ok(all_hits)
    }
    /// Parse `@[repo:name:label]` mentions from the input and resolve them to
    /// AgentContextChunks with repo metadata from the database.
    pub(crate) async fn agent_resolve_mentioned_repos(
        &self,
        workspace_id: Uuid,
        input: &str,
    ) -> Result<Vec<AgentContextChunk>, AppError> {
        let repo_names = extract_repo_mentions(input);
        if repo_names.is_empty() {
            return Ok(Vec::new());
        }

        let mut chunks = Vec::with_capacity(repo_names.len());
        for name in &repo_names {
            match self.resolve_repo_by_name(workspace_id, name).await {
                Ok(Some(repo)) => {
                    let content = format_repo_context(&repo);
                    chunks.push(AgentContextChunk::new(
                        format!("repo:{}", repo.name),
                        content,
                    ));
                    tracing::info!(
                        repo = %repo.name,
                        "injected repo context from @mention"
                    );
                }
                Ok(None) => {
                    tracing::debug!(
                        repo_name = %name,
                        "mentioned repo not found, skipping"
                    );
                }
                Err(e) => {
                    tracing::warn!(
                        repo_name = %name,
                        error = %e,
                        "failed to look up mentioned repo"
                    );
                }
            }
        }

        Ok(chunks)
    }

    /// Look up a single repo by workspace + name.
    async fn resolve_repo_by_name(
        &self,
        workspace_id: Uuid,
        name: &str,
    ) -> Result<Option<RepoModel>, AppError> {
        let repo = sqlx::query_as::<_, RepoModel>(
            "SELECT id, wk, name, description, default_branch, visibility, \
             size_bytes, is_archived, is_template, is_mirror, created_by, \
             storage_path, created_at, updated_at, deleted_at \
             FROM repo WHERE wk = $1 AND name = $2 AND deleted_at IS NULL",
        )
        .bind(workspace_id)
        .bind(name)
        .fetch_optional(self.db.reader())
        .await
        .map_err(|e| AppError::DatabaseError(e.to_string()))?;

        Ok(repo)
    }

    #[allow(dead_code)]
    pub(crate) async fn agent_upsert_knowledge(
        &self,
        ai_client: &AiClient,
        kb_id: Uuid,
        documents: Vec<RagDocument>,
    ) -> Result<(), AppError> {
        let qdrant_url = self
            .config
            .qdrant_url()
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;
        let vector_size = self
            .config
            .get_embed_model_dimensions()
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;

        let rag_config = RagConfig::new(qdrant_url, "agent_knowledge", vector_size)
            .map_err(|e| AppError::InternalServerError(e.to_string()))?
            .with_api_key(
                self.config
                    .qdrant_api_key()
                    .map_err(|e| AppError::InternalServerError(e.to_string()))?,
            );

        let rag = RagClient::connect(ai_client, rag_config)
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;
        rag.ensure_collection()
            .await
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;

        let session_key = format!("kb:{kb_id}");
        rag.upsert_documents(&session_key, documents)
            .await
            .map_err(|e| AppError::InternalServerError(e.to_string()))?;

        Ok(())
    }
}

// ---------------------------------------------------------------------------
// Repo mention helpers
// ---------------------------------------------------------------------------

/// Extract unique repo names from `@[repo:name:label]` mentions in the input.
fn extract_repo_mentions(input: &str) -> Vec<String> {
    let mut names = Vec::new();
    let mut seen = std::collections::HashSet::new();

    // Simple manual parser for @[repo:name:label]
    let bytes = input.as_bytes();
    let len = bytes.len();
    let mut i = 0;

    while i < len {
        // Look for "@[repo:"
        if i + 7 < len
            && bytes[i] == b'@'
            && bytes[i + 1] == b'['
            && bytes[i + 2] == b'r'
            && bytes[i + 3] == b'e'
            && bytes[i + 4] == b'p'
            && bytes[i + 5] == b'o'
            && bytes[i + 6] == b':'
        {
            let start = i + 7; // after "@[repo:"
            // Find the closing ']' — but skip ':' and the label part.
            // Format is @[repo:name:label], we want "name".
            if let Some(name_end) = input[start..].find(':') {
                let name = &input[start..start + name_end];
                if !name.is_empty() && seen.insert(name.to_string()) {
                    names.push(name.to_string());
                }
                // Skip past the closing ']'
                if let Some(closing) = input[start + name_end..].find(']') {
                    i = start + name_end + closing + 1;
                    continue;
                }
            }
        }
        i += 1;
    }

    names
}

/// Format a RepoModel into a concise context string for the AI.
fn format_repo_context(repo: &RepoModel) -> String {
    let mut s = format!(
        "Repository: {} (id: {})\n",
        repo.name, repo.id
    );
    if let Some(ref desc) = repo.description {
        if !desc.trim().is_empty() {
            s.push_str(&format!("Description: {}\n", desc.trim()));
        }
    }
    s.push_str(&format!("Default branch: {}\n", repo.default_branch));
    s.push_str(&format!("Visibility: {}\n", repo.visibility));
    if repo.is_archived {
        s.push_str("Status: archived\n");
    }
    if repo.is_template {
        s.push_str("Kind: template repository\n");
    }
    s.push_str(&format!(
        "Created: {}\n",
        repo.created_at.format("%Y-%m-%d")
    ));
    s
}

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

    #[test]
    fn test_extract_repo_mentions_single() {
        let input = "@[repo:my-repo:my-repo] what's the latest commit?";
        let names = extract_repo_mentions(input);
        assert_eq!(names, vec!["my-repo"]);
    }

    #[test]
    fn test_extract_repo_mentions_multiple() {
        let input = "compare @[repo:backend:backend] with @[repo:frontend:frontend]";
        let names = extract_repo_mentions(input);
        assert_eq!(names, vec!["backend", "frontend"]);
    }

    #[test]
    fn test_extract_repo_mentions_dedupe() {
        let input = "look at @[repo:a:a] and also @[repo:a:a] please";
        let names = extract_repo_mentions(input);
        assert_eq!(names, vec!["a"]);
    }

    #[test]
    fn test_extract_repo_mentions_none() {
        let input = "hello world no mentions here";
        let names = extract_repo_mentions(input);
        assert!(names.is_empty());
    }

    #[test]
    fn test_extract_ignores_other_mention_types() {
        let input = "@[user:abc:John] and @[repo:myrepo:myrepo]";
        let names = extract_repo_mentions(input);
        assert_eq!(names, vec!["myrepo"]);
    }
}