use std::sync::Arc;

use mistralai_client::v1::{
    chat::{ChatMessage, ChatParams, ResponseFormat},
    constants::Model,
};
use regex::Regex;
use tracing::{debug, info, warn};

use crate::config::Config;

#[derive(Debug)]
pub enum Engagement {
    MustRespond { reason: MustRespondReason },
    MaybeRespond { relevance: f32, hook: String },
    React { emoji: String, relevance: f32 },
    Ignore,
}

#[derive(Debug)]
pub enum MustRespondReason {
    DirectMention,
    DirectMessage,
    NameInvocation,
}

pub struct Evaluator {
    config: Arc<Config>,
    mention_regex: Regex,
    name_regex: Regex,
    /// Sol's system prompt — gives the evaluator full context on who Sol is.
    system_prompt: String,
}

impl Evaluator {
    // todo(sienna): regex must be configrable
    pub fn new(config: Arc<Config>, system_prompt: String) -> Self {
        let user_id = &config.matrix.user_id;
        // Match both plain @sol:sunbeam.pt and Matrix link format [sol](https://matrix.to/#/@sol:sunbeam.pt)
        let escaped = regex::escape(user_id);
        let mention_pattern = format!(r"{}|matrix\.to/#/{}", escaped, escaped);
        let mention_regex = Regex::new(&mention_pattern).expect("Failed to compile mention regex");
        let name_regex =
            Regex::new(r"(?i)(?:^|\bhey\s+)\bsol\b").expect("Failed to compile name regex");

        Self {
            config,
            mention_regex,
            name_regex,
            system_prompt,
        }
    }

    pub async fn evaluate(
        &self,
        sender: &str,
        body: &str,
        is_dm: bool,
        recent_messages: &[String],
        mistral: &Arc<mistralai_client::v1::client::Client>,
    ) -> Engagement {
        let body_preview: String = body.chars().take(80).collect();

        // Don't respond to ourselves
        if sender == self.config.matrix.user_id {
            debug!(sender, body = body_preview.as_str(), "Ignoring own message");
            return Engagement::Ignore;
        }

        // Direct mention: @sol:sunbeam.pt
        if self.mention_regex.is_match(body) {
            info!(sender, body = body_preview.as_str(), rule = "direct_mention", "Engagement: MustRespond");
            return Engagement::MustRespond {
                reason: MustRespondReason::DirectMention,
            };
        }

        // DM
        if is_dm {
            info!(sender, body = body_preview.as_str(), rule = "dm", "Engagement: MustRespond");
            return Engagement::MustRespond {
                reason: MustRespondReason::DirectMessage,
            };
        }

        // Name invocation: "sol ..." or "hey sol ..."
        if self.name_regex.is_match(body) {
            info!(sender, body = body_preview.as_str(), rule = "name_invocation", "Engagement: MustRespond");
            return Engagement::MustRespond {
                reason: MustRespondReason::NameInvocation,
            };
        }

        info!(
            sender, body = body_preview.as_str(),
            threshold = self.config.behavior.spontaneous_threshold,
            model = self.config.mistral.evaluation_model.as_str(),
            context_len = recent_messages.len(),
            eval_window = self.config.behavior.evaluation_context_window,
            detect_sol = self.config.behavior.detect_sol_in_conversation,
            "No rule match — running LLM relevance evaluation"
        );

        // Cheap evaluation call for spontaneous responses
        self.evaluate_relevance(body, recent_messages, mistral)
            .await
    }

    /// Check rule-based engagement (without calling Mistral). Returns Some(Engagement)
    /// if a rule matched, None if we need to fall through to the LLM evaluation.
    pub fn evaluate_rules(
        &self,
        sender: &str,
        body: &str,
        is_dm: bool,
    ) -> Option<Engagement> {
        if sender == self.config.matrix.user_id {
            return Some(Engagement::Ignore);
        }
        if self.mention_regex.is_match(body) {
            return Some(Engagement::MustRespond {
                reason: MustRespondReason::DirectMention,
            });
        }
        if is_dm {
            return Some(Engagement::MustRespond {
                reason: MustRespondReason::DirectMessage,
            });
        }
        if self.name_regex.is_match(body) {
            return Some(Engagement::MustRespond {
                reason: MustRespondReason::NameInvocation,
            });
        }
        None
    }

    async fn evaluate_relevance(
        &self,
        body: &str,
        recent_messages: &[String],
        mistral: &Arc<mistralai_client::v1::client::Client>,
    ) -> Engagement {
        let window = self.config.behavior.evaluation_context_window;
        let context = recent_messages
            .iter()
            .rev()
            .take(window)
            .rev()
            .cloned()
            .collect::<Vec<_>>()
            .join("\n");

        // Check if Sol recently participated in this conversation
        let sol_in_context = self.config.behavior.detect_sol_in_conversation
            && recent_messages.iter().any(|m| {
                let lower = m.to_lowercase();
                lower.starts_with("sol:") || lower.starts_with("sol ") || lower.contains("@sol:")
            });

        let default_active = "Sol is ALREADY part of this conversation (see messages above from Sol). \
             Messages that follow up on Sol's response, ask Sol a question, or continue \
             a thread Sol is in should score HIGH (0.8+). Sol should respond to follow-ups \
             directed at them even if not mentioned by name.".to_string();

        let default_passive = "Sol has NOT spoken in this conversation yet. Only score high if the message \
             is clearly relevant to Sol's expertise or touches a topic Sol has genuine insight on.".to_string();

        let participation_note = if sol_in_context {
            self.config.behavior.evaluation_prompt_active.as_deref()
                .unwrap_or(&default_active)
        } else {
            self.config.behavior.evaluation_prompt_passive.as_deref()
                .unwrap_or(&default_passive)
        };

        info!(
            sol_in_context,
            context_window = window,
            context_messages = recent_messages.len(),
            "Building evaluation prompt"
        );

        // System message: Sol's full personality + evaluation framing.
        // This gives the evaluator deep context on who Sol is, what they care about,
        // and how they'd naturally engage — so relevance scoring reflects Sol's actual character.
        let system = format!(
            "You are Sol's engagement evaluator. Your job is to decide whether Sol should \
             respond to a message in a group chat, based on Sol's personality, expertise, \
             and relationship with the people in the room.\n\n\
             # who sol is\n\n\
             {}\n\n\
             # your task\n\n\
             Read the conversation below and evaluate whether Sol would naturally want to \
             respond to the latest message. Consider:\n\
             - Does Sol have relevant knowledge, skills, or tools for this topic?\n\
             - Would Sol's personality naturally lead them to engage here?\n\
             - Is someone implicitly asking for Sol's help (even without mentioning them)?\n\
             - Is this a continuation of something Sol was already involved in?\n\
             - Would Sol find this genuinely interesting or have something meaningful to add?\n\
             - Would a reaction (emoji) be more appropriate than a full response?\n\n\
             {participation_note}\n\n\
             Respond ONLY with JSON:\n\
             {{\"relevance\": 0.0-1.0, \"hook\": \"brief reason or empty string\", \"emoji\": \"a single emoji or empty string\"}}\n\n\
             relevance=1.0 means Sol absolutely should respond, 0.0 means irrelevant.\n\
             hook: if responding, a brief note on what Sol would engage with.\n\
             emoji: if Sol wouldn't write a full response but might react, suggest a single \
             emoji that feels natural and specific — not generic thumbs up. leave empty if \
             no reaction fits.",
            self.system_prompt,
        );

        let user_prompt = format!(
            "# conversation\n\n{context}\n\n# latest message\n\n{body}"
        );

        let messages = vec![
            ChatMessage::new_system_message(&system),
            ChatMessage::new_user_message(&user_prompt),
        ];
        let params = ChatParams {
            response_format: Some(ResponseFormat::json_object()),
            temperature: Some(0.1),
            max_tokens: Some(150),
            ..Default::default()
        };

        let model = Model::new(&self.config.mistral.evaluation_model);
        let client = Arc::clone(mistral);
        let result = tokio::task::spawn_blocking(move || {
            client.chat(model, messages, Some(params))
        })
        .await
        .unwrap_or_else(|e| Err(mistralai_client::v1::error::ApiError {
            message: format!("spawn_blocking join error: {e}"),
        }));

        match result {
            Ok(response) => {
                let text = response.choices[0].message.content.text();
                info!(
                    raw_response = text.as_str(),
                    model = self.config.mistral.evaluation_model.as_str(),
                    "LLM evaluation raw response"
                );

                match serde_json::from_str::<serde_json::Value>(&text) {
                    Ok(val) => {
                        let relevance = val["relevance"].as_f64().unwrap_or(0.0) as f32;
                        let hook = val["hook"].as_str().unwrap_or("").to_string();
                        let emoji = val["emoji"].as_str().unwrap_or("").to_string();
                        let threshold = self.config.behavior.spontaneous_threshold;
                        let reaction_threshold = self.config.behavior.reaction_threshold;
                        let reaction_enabled = self.config.behavior.reaction_enabled;

                        info!(
                            relevance,
                            threshold,
                            reaction_threshold,
                            hook = hook.as_str(),
                            emoji = emoji.as_str(),
                            "LLM evaluation parsed"
                        );

                        if relevance >= threshold {
                            Engagement::MaybeRespond { relevance, hook }
                        } else if reaction_enabled
                            && relevance >= reaction_threshold
                            && !emoji.is_empty()
                        {
                            info!(
                                relevance,
                                emoji = emoji.as_str(),
                                "Reaction range — will react with emoji"
                            );
                            Engagement::React { emoji, relevance }
                        } else {
                            Engagement::Ignore
                        }
                    }
                    Err(e) => {
                        warn!(raw = text.as_str(), "Failed to parse evaluation response: {e}");
                        Engagement::Ignore
                    }
                }
            }
            Err(e) => {
                warn!("Evaluation call failed: {e}");
                Engagement::Ignore
            }
        }
    }
}

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

    fn test_config() -> Arc<Config> {
        let toml = r#"
[matrix]
homeserver_url = "https://chat.sunbeam.pt"
user_id = "@sol:sunbeam.pt"
state_store_path = "/tmp/sol"

[opensearch]
url = "http://localhost:9200"
index = "test"

[mistral]
[behavior]
"#;
        Arc::new(Config::from_str(toml).unwrap())
    }

    fn evaluator() -> Evaluator {
        Evaluator::new(test_config(), "you are sol, a virtual librarian.".to_string())
    }

    #[test]
    fn test_ignore_own_messages() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@sol:sunbeam.pt", "hello everyone", false);
        assert!(matches!(result, Some(Engagement::Ignore)));
    }

    #[test]
    fn test_direct_mention() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "hey @sol:sunbeam.pt what's up?", false);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::DirectMention })
        ));
    }

    #[test]
    fn test_dm_detection() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "random message", true);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::DirectMessage })
        ));
    }

    #[test]
    fn test_name_invocation_start_of_message() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "sol, can you find that link?", false);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::NameInvocation })
        ));
    }

    #[test]
    fn test_name_invocation_hey_sol() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "hey sol do you remember?", false);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::NameInvocation })
        ));
    }

    #[test]
    fn test_name_invocation_case_insensitive() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "Hey Sol, help me", false);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::NameInvocation })
        ));
    }

    #[test]
    fn test_name_invocation_sol_uppercase() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "SOL what do you think?", false);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::NameInvocation })
        ));
    }

    #[test]
    fn test_no_false_positive_solstice() {
        let ev = evaluator();
        // "solstice" should NOT trigger name invocation — \b boundary prevents it
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "the solstice is coming", false);
        assert!(result.is_none());
    }

    #[test]
    fn test_random_message_falls_through() {
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "what's for lunch?", false);
        assert!(result.is_none());
    }

    #[test]
    fn test_priority_mention_over_dm() {
        // When both mention and DM are true, mention should match first
        let ev = evaluator();
        let result = ev.evaluate_rules("@alice:sunbeam.pt", "hi @sol:sunbeam.pt", true);
        assert!(matches!(
            result,
            Some(Engagement::MustRespond { reason: MustRespondReason::DirectMention })
        ));
    }
}