use std::path::{Path, PathBuf};

use reqwest::Client;
use yup_oauth2::{
    authenticator::Authenticator, hyper::client::connect::HttpConnector,
    hyper_rustls::HttpsConnector, InstalledFlowAuthenticator, InstalledFlowReturnMethod,
};

use crate::domain::models::*;

#[derive(Debug)]
pub enum ApiError {
    Network(String),
    Auth(String),
    Api(String),
}

impl std::fmt::Display for ApiError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            ApiError::Network(s) => write!(f, "Network error: {}", s),
            ApiError::Auth(s) => write!(f, "Auth error: {}", s),
            ApiError::Api(s) => write!(f, "API error: {}", s),
        }
    }
}

impl std::error::Error for ApiError {}

pub struct ApiClient {
    client: Client,
    authenticator: Authenticator<HttpsConnector<HttpConnector>>,
    token_path: PathBuf,
}

const SCOPES: &[&str] = &[
    "https://www.googleapis.com/auth/tasks",
    "https://www.googleapis.com/auth/calendar.readonly",
];

impl ApiClient {
    pub async fn new(secret_path: impl AsRef<Path>) -> Result<Self, ApiError> {
        let token_path = dirs::config_dir()
            .unwrap_or_else(|| PathBuf::from("."))
            .join("task_app")
            .join("token.json");

        if let Some(parent) = token_path.parent() {
            std::fs::create_dir_all(parent).ok();
        }

        let secret = yup_oauth2::read_application_secret(secret_path)
            .await
            .map_err(|e| ApiError::Auth(format!("Failed to read secret file: {}", e)))?;

        let authenticator = InstalledFlowAuthenticator::builder(
            secret,
            InstalledFlowReturnMethod::HTTPRedirect,
        )
        .persist_tokens_to_disk(token_path.clone())
        .build()
        .await
        .map_err(|e| ApiError::Auth(format!("Failed to build authenticator: {}", e)))?;

        Ok(Self {
            client: Client::new(),
            authenticator,
            token_path,
        })
    }

    pub fn has_token(&self) -> bool {
        self.token_path.exists()
    }

    pub fn token_has_all_scopes(&self) -> bool {
        let content = match std::fs::read_to_string(&self.token_path) {
            Ok(c) => c,
            Err(_) => return false,
        };
        let entries: Vec<serde_json::Value> = match serde_json::from_str(&content) {
            Ok(v) => v,
            Err(_) => return false,
        };
        for entry in &entries {
            let scopes = match entry["scopes"].as_array() {
                Some(s) => s,
                None => continue,
            };
            let has_all: Vec<&str> = scopes
                .iter()
                .filter_map(|s| s.as_str())
                .collect();
            if SCOPES.iter().all(|s| has_all.contains(s)) {
                return true;
            }
        }
        false
    }

    pub async fn start_and_wait_for_auth(&self) -> Result<(), ApiError> {
        self.authenticator.token(SCOPES).await.map_err(|e| {
            ApiError::Auth(format!("Authorization failed: {}", e))
        })?;
        Ok(())
    }

    async fn get_token(&self) -> Result<String, ApiError> {
        let token = self
            .authenticator
            .token(SCOPES)
            .await
            .map_err(|e| ApiError::Auth(format!("Token error: {}", e)))?;
        Ok(token.token().unwrap_or("").to_string())
    }

    pub async fn fetch_lists(&self) -> Result<Vec<TaskList>, ApiError> {
        let token = self.get_token().await?;

        let resp = self
            .client
            .get("https://tasks.googleapis.com/tasks/v1/users/@me/lists")
            .bearer_auth(&token)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Fetch lists failed: {} - {}", status, body)));
        }

        let data: serde_json::Value = resp
            .json()
            .await
            .map_err(|e| ApiError::Api(e.to_string()))?;

        let empty = vec![];
        let items = data["items"].as_array().unwrap_or(&empty);
        let lists = items
            .iter()
            .map(|item| TaskList {
                id: item["id"].as_str().unwrap_or("").to_string(),
                title: item["title"].as_str().unwrap_or("").to_string(),
            })
            .collect();

        Ok(lists)
    }

    pub async fn fetch_tasks(&self, list_id: &str) -> Result<Vec<Task>, ApiError> {
        let token = self.get_token().await?;

        let mut all_items: Vec<serde_json::Value> = Vec::new();
        let mut page_token: Option<String> = None;

        loop {
            let mut url = format!(
                "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks?showCompleted=true&showHidden=true&maxResults=100",
                list_id
            );
            if let Some(ref pt) = page_token {
                url.push_str(&format!("&pageToken={}", pt));
            }

            let resp = self
                .client
                .get(&url)
                .bearer_auth(&token)
                .send()
                .await
                .map_err(|e| ApiError::Network(e.to_string()))?;

            if !resp.status().is_success() {
                let status = resp.status();
                let body = resp.text().await.unwrap_or_default();
                return Err(ApiError::Api(format!("Fetch tasks failed: {} - {}", status, body)));
            }

            let data: serde_json::Value = resp
                .json()
                .await
                .map_err(|e| ApiError::Api(e.to_string()))?;

            if let Some(items) = data["items"].as_array() {
                all_items.extend(items.iter().cloned());
            }

            match data["nextPageToken"].as_str() {
                Some(token) if !token.is_empty() => page_token = Some(token.to_string()),
                _ => break,
            }
        }

        let tasks = all_items
            .iter()
            .enumerate()
            .map(|(i, item)| parse_task_value(item, list_id, i))
            .collect();

        Ok(tasks)
    }

    pub async fn fetch_tasks_since(&self, list_id: &str, since: &chrono::NaiveDateTime) -> Result<Vec<Task>, ApiError> {
        let token = self.get_token().await?;
        let since_str = since.format("%Y-%m-%dT%H:%M:%S.000Z").to_string();

        let mut all_items: Vec<serde_json::Value> = Vec::new();
        let mut page_token: Option<String> = None;

        loop {
            let mut url = format!(
                "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks?showCompleted=true&showHidden=true&maxResults=100&updatedMin={}",
                list_id, since_str
            );
            if let Some(ref pt) = page_token {
                url.push_str(&format!("&pageToken={}", pt));
            }

            let resp = self
                .client
                .get(&url)
                .bearer_auth(&token)
                .send()
                .await
                .map_err(|e| ApiError::Network(e.to_string()))?;

            if !resp.status().is_success() {
                let status = resp.status();
                let body = resp.text().await.unwrap_or_default();
                return Err(ApiError::Api(format!("Fetch tasks since failed: {} - {}", status, body)));
            }

            let data: serde_json::Value = resp
                .json()
                .await
                .map_err(|e| ApiError::Api(e.to_string()))?;

            if let Some(items) = data["items"].as_array() {
                all_items.extend(items.iter().cloned());
            }

            match data["nextPageToken"].as_str() {
                Some(token) if !token.is_empty() => page_token = Some(token.to_string()),
                _ => break,
            }
        }

        let tasks = all_items
            .iter()
            .enumerate()
            .map(|(i, item)| parse_task_value(item, list_id, i))
            .collect();

        Ok(tasks)
    }

    pub async fn create_task(&self, list_id: &str, task: &Task) -> Result<Task, ApiError> {
        let token = self.get_token().await?;

        let mut body = serde_json::json!({
            "title": task.title,
        });

        if let Some(ref notes) = task.notes {
            body["notes"] = serde_json::Value::String(notes.clone());
        }
        if let Some(due) = task.due {
            body["due"] =
                serde_json::Value::String(due.format("%Y-%m-%dT%H:%M:00.000Z").to_string());
        }
        if task.status == TaskStatus::Completed {
            body["status"] = serde_json::Value::String("completed".to_string());
        }

        let url = format!(
            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks",
            list_id
        );

        let resp = self
            .client
            .post(&url)
            .bearer_auth(&token)
            .json(&body)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body_text = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Create failed: {} - {}", status, body_text)));
        }

        let data: serde_json::Value = resp
            .json()
            .await
            .map_err(|e| ApiError::Api(format!("Create parse error: {}", e)))?;

        Ok(parse_task_value(&data, list_id, 0))
    }

    pub async fn create_list(&self, title: &str) -> Result<TaskList, ApiError> {
        let token = self.get_token().await?;

        let body = serde_json::json!({ "title": title });

        let resp = self
            .client
            .post("https://tasks.googleapis.com/tasks/v1/users/@me/lists")
            .bearer_auth(&token)
            .json(&body)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body_text = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Create list failed: {} - {}", status, body_text)));
        }

        let data: serde_json::Value = resp
            .json()
            .await
            .map_err(|e| ApiError::Api(format!("Create list parse error: {}", e)))?;

        Ok(TaskList {
            id: data["id"].as_str().unwrap_or("").to_string(),
            title: data["title"].as_str().unwrap_or("").to_string(),
        })
    }

    pub async fn update_task(&self, list_id: &str, task: &Task) -> Result<(), ApiError> {
        let token = self.get_token().await?;

        let mut body = serde_json::json!({
            "title": task.title,
        });

        if let Some(ref notes) = task.notes {
            body["notes"] = serde_json::Value::String(notes.clone());
        }
        if let Some(due) = task.due {
            body["due"] =
                serde_json::Value::String(due.format("%Y-%m-%dT%H:%M:00.000Z").to_string());
        }
        body["status"] = serde_json::Value::String(match task.status {
            TaskStatus::Completed => "completed".to_string(),
            TaskStatus::NeedsAction => "needsAction".to_string(),
        });

        let url = format!(
            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}",
            list_id, task.id
        );

        let resp = self
            .client
            .patch(&url)
            .bearer_auth(&token)
            .json(&body)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            return Err(ApiError::Api(format!(
                "Update failed: {}",
                resp.status()
            )));
        }

        Ok(())
    }

    pub async fn delete_task(&self, list_id: &str, task_id: &str) -> Result<(), ApiError> {
        let token = self.get_token().await?;

        let url = format!(
            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}",
            list_id, task_id
        );

        let resp = self
            .client
            .delete(&url)
            .bearer_auth(&token)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            // 404 means already deleted — treat as success
            if resp.status() == 404 {
                return Ok(());
            }
            return Err(ApiError::Api(format!(
                "Delete failed: {}",
                resp.status()
            )));
        }

        Ok(())
    }

    pub async fn delete_list(&self, list_id: &str) -> Result<(), ApiError> {
        let token = self.get_token().await?;

        let url = format!(
            "https://tasks.googleapis.com/tasks/v1/users/@me/lists/{}",
            list_id
        );

        let resp = self
            .client
            .delete(&url)
            .bearer_auth(&token)
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            // 404 means already deleted — treat as success
            if status == 404 {
                return Ok(());
            }
            let body = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Delete list failed: {} - {}", status, body)));
        }

        Ok(())
    }

    pub async fn move_task(
        &self,
        list_id: &str,
        task_id: &str,
        prev: Option<&str>,
        sibling: Option<&str>,
    ) -> Result<(), ApiError> {
        let token = self.get_token().await?;

        let url = format!(
            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}/move",
            list_id, task_id
        );

        let mut req = self.client.post(&url).bearer_auth(&token);
        if let Some(p) = prev {
            req = req.query(&[("previous", p)]);
        }
        if let Some(s) = sibling {
            req = req.query(&[("destinationTaskList", s)]);
        }

        let resp = req
            .header(reqwest::header::CONTENT_LENGTH, "0")
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Move failed: {} - {}", status, body)));
        }

        Ok(())
    }

    pub async fn fetch_upcoming_events(&self, max_results: u32) -> Result<Vec<CalendarEvent>, ApiError> {
        let token = self.get_token().await?;

        let now = chrono::Utc::now();
        let end_time = now + chrono::Duration::days(30);

        let resp = self
            .client
            .get("https://www.googleapis.com/calendar/v3/calendars/primary/events")
            .bearer_auth(&token)
            .query(&[
                ("orderBy", "startTime"),
                ("singleEvents", "true"),
                ("timeMin", &now.format("%Y-%m-%dT%H:%M:%SZ").to_string()),
                ("timeMax", &end_time.format("%Y-%m-%dT%H:%M:%SZ").to_string()),
                ("maxResults", &max_results.to_string()),
            ])
            .send()
            .await
            .map_err(|e| ApiError::Network(e.to_string()))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body = resp.text().await.unwrap_or_default();
            return Err(ApiError::Api(format!("Calendar fetch failed: {} - {}", status, body)));
        }

        let body: serde_json::Value = resp.json().await
            .map_err(|e| ApiError::Api(format!("Calendar JSON parse error: {}", e)))?;

        let items = body["items"].as_array()
            .map(|arr| {
                arr.iter().filter_map(|item| {
                    let summary = item["summary"].as_str()?.to_string();
                    let start = parse_calendar_time(&item["start"]);
                    let end = parse_calendar_time(&item["end"]);
                    let location = item["location"].as_str().map(|s| s.to_string());
                    Some(CalendarEvent { summary, start, end, location })
                }).collect::<Vec<_>>()
            })
            .unwrap_or_default();

        Ok(items)
    }
}

fn parse_task_value(item: &serde_json::Value, list_id: &str, position: usize) -> Task {
    let due_str = item["due"].as_str().and_then(|s| {
        chrono::NaiveDateTime::parse_from_str(
            &s.replace("T", " ")
                .replace("Z", "")
                .chars()
                .take(16)
                .collect::<String>(),
            "%Y-%m-%d %H:%M",
        )
        .ok()
    });

    let updated = item["updated"].as_str().and_then(|s| {
        chrono::NaiveDateTime::parse_from_str(
            &s.replace("T", " ")
                .replace("Z", "")
                .chars()
                .take(19)
                .collect::<String>(),
            "%Y-%m-%d %H:%M:%S",
        )
        .ok()
    });

    Task {
        id: item["id"].as_str().unwrap_or("").to_string(),
        list_id: list_id.to_string(),
        title: item["title"].as_str().unwrap_or("").to_string(),
        notes: item["notes"].as_str().map(|s| s.to_string()),
        status: if item["status"].as_str() == Some("completed") {
            TaskStatus::Completed
        } else {
            TaskStatus::NeedsAction
        },
        due: due_str,
        position: position as i64,
        created_at: None,
        updated_at: updated,
    }
}

fn parse_calendar_time(obj: &serde_json::Value) -> Option<chrono::NaiveDateTime> {
    if let Some(dt) = obj["dateTime"].as_str() {
        chrono::DateTime::parse_from_rfc3339(dt).ok().map(|d| d.naive_local())
    } else if let Some(d) = obj["date"].as_str() {
        chrono::NaiveDate::parse_from_str(d, "%Y-%m-%d").ok()
            .map(|date| date.and_hms_opt(0, 0, 0).unwrap())
    } else {
        None
    }
}