use std::time::Duration;

use chrono::Utc;
use color_eyre::{
    eyre::{eyre, WrapErr},
    Result,
};
use lazy_static::lazy_static;
use reqwest::{Client, StatusCode};
use reqwest_middleware::{ClientBuilder, ClientWithMiddleware, RequestBuilder};
use reqwest_retry::{policies::ExponentialBackoff, RetryTransientMiddleware};
use serde::{de::DeserializeOwned, Serialize};
use uuid::Uuid;

use super::{
    Comment, CreateComment, CreateLabel, CreateProject, CreateSection, CreateTask, Label, LabelID,
    Project, ProjectID, Section, SectionID, Task, TaskDue, TaskID, UpdateTask,
};

/// Makes network calls to the Todoist API and returns structs that can then be worked with.
pub struct Gateway {
    client: ClientWithMiddleware,
    token: String,
    url: url::Url,
}

lazy_static! {
    /// The default URL that specifies the endpont to use for the Todoist API.
    pub static ref TODOIST_API_URL: url::Url = {
        url::Url::parse("https://api.todoist.com/").unwrap()
    };
}

impl Gateway {
    /// Create a new [`Gateway`].
    ///
    /// * `token` - the API token used for network calls.
    /// * `url` - the base URL to call. See [`struct@TODOIST_API_URL`]
    pub fn new(token: &str, url: &url::Url) -> Gateway {
        let retry_policy = ExponentialBackoff::builder().build_with_max_retries(3);
        let client = ClientBuilder::new(Client::new())
            .with(RetryTransientMiddleware::new_with_policy(retry_policy))
            .build();
        Gateway {
            client,
            token: token.to_string(),
            url: url.clone(),
        }
    }

    /// Retuns a [`Task`].
    ///
    /// * `id` - the ID as used by the Todoist API.
    pub async fn task(&self, id: &TaskID) -> Result<Task> {
        self.get::<(), _>(&format!("rest/v2/tasks/{}", id), None)
            .await
            .wrap_err("unable to get task")
    }

    /// Returns a list of tasks as given by the API.
    ///
    /// * `filter` - a filter query as described in the [documentation](https://todoist.com/help/articles/205248842).
    pub async fn tasks(&self, filter: Option<&str>) -> Result<Vec<Task>> {
        self.get(
            "rest/v2/tasks",
            filter.map(|filter| vec![("filter", filter)]),
        )
        .await
        .wrap_err("unable to get tasks")
    }

    /// Closes a task.
    ///
    /// Equivalent to pushing the circle in the UI.
    pub async fn close(&self, id: &TaskID) -> Result<()> {
        self.post_empty(
            &format!("rest/v2/tasks/{}/close", id),
            &serde_json::Map::new(),
        )
        .await
        .wrap_err("unable to close task")?;
        Ok(())
    }

    /// Complete will complete a task by first updating the due date to today, so if it's
    /// recurring, it will stop doing that.
    /// This is a bit hacky, but the REST API does not support completely closing tasks without
    /// deleting them.
    pub async fn complete(&self, id: &TaskID) -> Result<()> {
        self.update(
            id,
            &UpdateTask {
                due: Some(TaskDue::DateTime(Utc::now())),
                ..Default::default()
            },
        )
        .await
        .wrap_err("unable to complete task")?;
        self.close(id).await.wrap_err("unable to complete task")?;
        Ok(())
    }

    /// Creates a task by calling the Todoist API.
    pub async fn create(&self, task: &CreateTask) -> Result<Task> {
        self.post("rest/v2/tasks", task)
            .await
            .wrap_err("unable to create task")?
            .ok_or_else(|| eyre!("unable to create task"))
    }

    /// Updates a task with the data as specified in UpdateTask.
    pub async fn update(&self, id: &TaskID, task: &UpdateTask) -> Result<()> {
        self.post_empty(&format!("rest/v2/tasks/{}", id), &task)
            .await
            .wrap_err("unable to update task")?;
        Ok(())
    }

    /// Returns the list of Projects.
    pub async fn projects(&self) -> Result<Vec<Project>> {
        self.get::<(), _>("rest/v2/projects", None)
            .await
            .wrap_err("unable to get projects")
    }

    /// Returns the list of all Sections.
    pub async fn sections(&self) -> Result<Vec<Section>> {
        self.get::<(), _>("rest/v2/sections", None)
            .await
            .wrap_err("unable to get sections")
    }

    /// Returns the list of all Labels.
    pub async fn labels(&self) -> Result<Vec<Label>> {
        self.get::<(), _>("rest/v2/labels", None)
            .await
            .wrap_err("unable to get labels")
    }

    /// Returns the list of all comments attached to the given Project.
    pub async fn project_comments(&self, id: &ProjectID) -> Result<Vec<Comment>> {
        self.get("rest/v2/comments", Some(&[("project_id", id)]))
            .await
            .wrap_err("unable to get comments")
    }

    /// Returns the list of all comments attached to the given Task.
    pub async fn task_comments(&self, id: &TaskID) -> Result<Vec<Comment>> {
        self.get("rest/v2/comments", Some(&[("task_id", id)]))
            .await
            .wrap_err("unable to get comments")
    }

    /// Creates a comment by calling the API.
    pub async fn create_comment(&self, comment: &CreateComment) -> Result<Comment> {
        self.post("rest/v2/comments", comment)
            .await
            .wrap_err("unable to create comment")?
            .ok_or_else(|| eyre!("unable to create comment"))
    }

    /// Returns details about a single project.
    ///
    /// * `id` - the ID as used by the Todoist API.
    pub async fn project(&self, id: &ProjectID) -> Result<Project> {
        self.get::<(), _>(&format!("rest/v2/projects/{}", id), None)
            .await
            .wrap_err("unable to get project")
    }

    /// Creates a project by calling the Todoist API.
    pub async fn create_project(&self, project: &CreateProject) -> Result<Project> {
        self.post("rest/v2/projects", project)
            .await
            .wrap_err("unable to create project")?
            .ok_or_else(|| eyre!("unable to create project"))
    }

    /// Deletes a project by calling the Todoist API.
    pub async fn delete_project(&self, project: &ProjectID) -> Result<()> {
        self.delete(&format!("rest/v2/projects/{}", project))
            .await
            .wrap_err("unable to delete project")
    }

    /// Returns details about a single section.
    ///
    /// * `id` - the ID as used by the Todoist API.
    pub async fn section(&self, id: &SectionID) -> Result<Section> {
        self.get::<(), _>(&format!("rest/v2/sections/{}", id), None)
            .await
            .wrap_err("unable to get section")
    }

    /// Creates a section by calling the Todoist API.
    pub async fn create_section(&self, section: &CreateSection) -> Result<Section> {
        self.post("rest/v2/sections", section)
            .await
            .wrap_err("unable to create section")?
            .ok_or_else(|| eyre!("unable to create section"))
    }

    /// Deletes a section by calling the Todoist API.
    pub async fn delete_section(&self, section: &SectionID) -> Result<()> {
        self.delete(&format!("rest/v2/sections/{}", section))
            .await
            .wrap_err("unable to delete section")
    }

    /// Returns details about a single label.
    ///
    /// * `id` - the ID as used by the Todoist API.
    pub async fn label(&self, id: &LabelID) -> Result<Label> {
        self.get::<(), _>(&format!("rest/v2/labels/{}", id), None)
            .await
            .wrap_err("unable to get label")
    }

    /// Creates a label by calling the Todoist API.
    pub async fn create_label(&self, label: &CreateLabel) -> Result<Label> {
        self.post("rest/v2/labels", label)
            .await
            .wrap_err("unable to create label")?
            .ok_or_else(|| eyre!("unable to create label"))
    }

    /// Deletes a label by calling the Todoist API.
    pub async fn delete_label(&self, label: &LabelID) -> Result<()> {
        self.delete(&format!("rest/v2/labels/{}", label))
            .await
            .wrap_err("unable to delete label")
    }

    /// Makes a GET request to the Todoist API with an optional query.
    async fn get<'a, T: 'a + Serialize, R: DeserializeOwned>(
        &self,
        path: &str,
        query: Option<T>,
    ) -> Result<R> {
        let req = self
            .client
            .get(self.url.join(path)?)
            .bearer_auth(&self.token);
        let req = if let Some(q) = query {
            req.query(&q)
        } else {
            req
        };
        handle_req(req)
            .await?
            .ok_or_else(|| eyre!("Invalid response from API"))
    }

    /// Sends a POST request to the Todoist API with the given content.
    async fn post<T: Serialize, R: DeserializeOwned>(
        &self,
        path: &str,
        content: &T,
    ) -> Result<Option<R>> {
        let uuid = Uuid::new_v4();
        handle_req(
            self.client
                .post(self.url.join(path)?)
                .bearer_auth(&self.token)
                .body(serde_json::to_string(&content)?)
                .header(reqwest::header::CONTENT_TYPE, "application/json")
                .header("X-Request-Id", uuid.to_string()),
        )
        .await
    }

    /// Sends a DELETE request to the Todoist API.
    async fn delete(&self, path: &str) -> Result<()> {
        handle_req::<()>(
            self.client
                .delete(self.url.join(path)?)
                .bearer_auth(&self.token),
        )
        .await?;
        Ok(())
    }

    /// Same as [`Gateway::post`], but doesn't require content to be set for the POST request.
    async fn post_empty<T: Serialize>(&self, path: &str, content: &T) -> Result<()> {
        self.post::<_, String>(path, content).await?;
        Ok(())
    }
}

/// Does the actual call to the Todoist API and handles error handling.
async fn handle_req<R: DeserializeOwned>(req: RequestBuilder) -> Result<Option<R>> {
    // TODO: implement retries/backoffs
    let resp = req
        .timeout(Duration::from_secs(30))
        .send()
        .await
        .wrap_err("unable to send request")?;
    let status = resp.status();
    if status == StatusCode::NO_CONTENT {
        return Ok(None);
    }
    let text = resp.text().await.wrap_err("unable to read response")?;
    if !status.is_success() {
        return Err(eyre!("Bad response from API: {} - {}", status, text));
    }
    let result = serde_json::from_str(&text).wrap_err("unable to parse API response")?;
    Ok(Some(result))
}

#[cfg(test)]
mod test {
    use wiremock::{
        matchers::{bearer_token, method, path, query_param},
        Mock, MockServer, ResponseTemplate,
    };

    use super::*;
    use crate::api::rest::{Task, ThreadID};
    use color_eyre::Result;

    #[tokio::test]
    async fn has_authentication() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(bearer_token("hellothere"))
            .and(path("/rest/v2/tasks/123"))
            .respond_with(
                ResponseTemplate::new(200).set_body_json(create_task("123", "456", "hello")),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("hellothere", &mock_server);
        let task = gw.task(&"123".to_string()).await;
        assert!(task.is_ok());
    }

    #[tokio::test]
    async fn task() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/tasks/123"))
            .respond_with(
                ResponseTemplate::new(200).set_body_json(create_task("123", "456", "hello")),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let task = gw.task(&"123".to_string()).await.unwrap();
        mock_server.verify().await;
        assert_eq!(task.id, "123");
        assert!(gw.task(&"1234".to_string()).await.is_err());
    }

    #[tokio::test]
    async fn tasks() -> Result<()> {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/tasks"))
            .respond_with(ResponseTemplate::new(200).set_body_json(&[
                create_task("123", "456", "hello there"),
                create_task("234", "567", "general kenobi"),
            ]))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let tasks = gw.tasks(None).await.unwrap();
        mock_server.verify().await;
        assert_eq!(tasks.len(), 2);
        Ok(())
    }

    #[tokio::test]
    async fn close_task() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/tasks/123/close"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let closed = gw.close(&"123".to_string()).await;
        assert!(closed.is_ok());
    }

    #[tokio::test]
    async fn complete_task() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/tasks/123"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/tasks/123/close"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let completed = gw.complete(&"123".to_string()).await;
        mock_server.verify().await;
        assert!(completed.is_ok());
    }

    #[tokio::test]
    async fn update_task() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/tasks/123"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let completed = gw
            .update(
                &"123".to_string(),
                &UpdateTask {
                    content: Some("hello".to_string()),
                    ..Default::default()
                },
            )
            .await;
        mock_server.verify().await;
        assert!(completed.is_ok());
    }

    #[tokio::test]
    async fn creates_task() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/tasks"))
            .respond_with(
                ResponseTemplate::new(200).set_body_json(create_task("123", "456", "hello")),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let task = gw
            .create(&CreateTask {
                content: "hello".to_string(),
                project_id: Some("456".to_string()),
                ..Default::default()
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(task.id, "123");
    }

    #[tokio::test]
    async fn lists_projects() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/projects"))
            .respond_with(
                ResponseTemplate::new(200)
                    .set_body_json(vec![Project::new("123", "one"), Project::new("456", "two")]),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let projects = gw.projects().await.unwrap();
        mock_server.verify().await;
        assert_eq!(projects.len(), 2);
    }

    #[tokio::test]
    async fn show_project() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/projects/123"))
            .respond_with(ResponseTemplate::new(200).set_body_json(Project::new("123", "one")))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let project = gw.project(&"123".to_string()).await.unwrap();
        mock_server.verify().await;
        assert_eq!(project.id, "123");
        assert_eq!(project.name, "one");
    }

    #[tokio::test]
    async fn lists_labels() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/labels"))
            .respond_with(
                ResponseTemplate::new(200)
                    .set_body_json(vec![Label::new("123", "one"), Label::new("456", "two")]),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let labels = gw.labels().await.unwrap();
        mock_server.verify().await;
        assert_eq!(labels.len(), 2);
    }

    #[tokio::test]
    async fn show_label() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/labels/123"))
            .respond_with(ResponseTemplate::new(200).set_body_json(Label::new("123", "one")))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let label = gw.label(&"123".to_string()).await.unwrap();
        mock_server.verify().await;
        assert_eq!(label.id, "123");
        assert_eq!(label.name, "one");
    }

    #[tokio::test]
    async fn lists_sections() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/sections"))
            .respond_with(ResponseTemplate::new(200).set_body_json(vec![
                Section::new("123", "1", "one"),
                Section::new("456", "2", "two"),
            ]))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let sections = gw.sections().await.unwrap();
        mock_server.verify().await;
        assert_eq!(sections.len(), 2);
    }

    #[tokio::test]
    async fn show_section() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/sections/123"))
            .respond_with(ResponseTemplate::new(200).set_body_json(Section::new("123", "1", "one")))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let section = gw.section(&"123".to_string()).await.unwrap();
        mock_server.verify().await;
        assert_eq!(section.id, "123");
        assert_eq!(section.name, "one");
    }

    #[tokio::test]
    async fn create_project_comment() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/comments"))
            .respond_with(ResponseTemplate::new(200).set_body_json(create_comment(
                "1",
                ThreadID::Project {
                    project_id: "123".to_string(),
                },
                "hello",
            )))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let comment = gw
            .create_comment(&CreateComment {
                thread: ThreadID::Project {
                    project_id: "123".to_string(),
                },
                content: "hello".to_string(),
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(comment.id, "1");
        assert_eq!(comment.content, "hello");
    }

    #[tokio::test]
    async fn create_task_comment() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/comments"))
            .respond_with(ResponseTemplate::new(200).set_body_json(create_comment(
                "1",
                ThreadID::Task {
                    task_id: "123".to_string(),
                },
                "hello",
            )))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let comment = gw
            .create_comment(&CreateComment {
                thread: ThreadID::Task {
                    task_id: "123".to_string(),
                },
                content: "hello".to_string(),
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(comment.id, "1");
        assert_eq!(comment.content, "hello");
    }

    #[tokio::test]
    async fn show_comments() {
        let mock_server = MockServer::start().await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/comments"))
            .and(query_param("project_id", "123"))
            .respond_with(ResponseTemplate::new(200).set_body_json(vec![
                create_comment(
                    "1",
                    ThreadID::Project {
                        project_id: "123".to_string(),
                    },
                    "hello",
                ),
                create_comment(
                    "1",
                    ThreadID::Project {
                        project_id: "123".to_string(),
                    },
                    "there",
                ),
            ]))
            .mount(&mock_server)
            .await;
        Mock::given(method("GET"))
            .and(path("/rest/v2/comments"))
            .and(query_param("task_id", "456"))
            .respond_with(ResponseTemplate::new(200).set_body_json(vec![
                create_comment(
                    "1",
                    ThreadID::Task {
                        task_id: "456".to_string(),
                    },
                    "no",
                ),
                create_comment(
                    "1",
                    ThreadID::Task {
                        task_id: "456".to_string(),
                    },
                    "way",
                ),
            ]))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let project_comments = gw.project_comments(&"123".to_string()).await.unwrap();
        let task_comments = gw.task_comments(&"456".to_string()).await.unwrap();
        mock_server.verify().await;
        assert_eq!(project_comments.len(), 2);
        assert_eq!(project_comments[0].content, "hello");
        assert_eq!(task_comments.len(), 2);
        assert_eq!(task_comments[0].content, "no");
    }

    #[tokio::test]
    async fn creates_label() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/labels"))
            .respond_with(ResponseTemplate::new(200).set_body_json(Label::new("123", "hello")))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let label = gw
            .create_label(&CreateLabel {
                name: "hello".to_string(),
                ..Default::default()
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(label.id, "123");
    }

    #[tokio::test]
    async fn delete_label() {
        let mock_server = MockServer::start().await;
        Mock::given(method("DELETE"))
            .and(path("/rest/v2/labels/123"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let closed = gw.delete_label(&"123".to_string()).await;
        assert!(closed.is_ok());
    }

    #[tokio::test]
    async fn creates_project() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/projects"))
            .respond_with(ResponseTemplate::new(200).set_body_json(Project::new("123", "hello")))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let project = gw
            .create_project(&CreateProject {
                name: "hello".to_string(),
                ..Default::default()
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(project.id, "123");
    }

    #[tokio::test]
    async fn delete_project() {
        let mock_server = MockServer::start().await;
        Mock::given(method("DELETE"))
            .and(path("/rest/v2/projects/123"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let closed = gw.delete_project(&"123".to_string()).await;
        assert!(closed.is_ok());
    }

    fn gateway(token: &str, ms: &MockServer) -> Gateway {
        Gateway::new(token, &ms.uri().parse().unwrap())
    }

    #[tokio::test]
    async fn creates_section() {
        let mock_server = MockServer::start().await;
        Mock::given(method("POST"))
            .and(path("/rest/v2/sections"))
            .respond_with(
                ResponseTemplate::new(200).set_body_json(Section::new("123", "456", "heya")),
            )
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let section = gw
            .create_section(&CreateSection {
                name: "hello".to_string(),
                project_id: "456".to_string(),
                ..Default::default()
            })
            .await
            .unwrap();
        mock_server.verify().await;
        assert_eq!(section.id, "123");
        assert_eq!(section.project_id, "456");
    }

    #[tokio::test]
    async fn delete_section() {
        let mock_server = MockServer::start().await;
        Mock::given(method("DELETE"))
            .and(path("/rest/v2/sections/123"))
            .respond_with(ResponseTemplate::new(204))
            .mount(&mock_server)
            .await;
        let gw = gateway("", &mock_server);
        let closed = gw.delete_section(&"123".to_string()).await;
        assert!(closed.is_ok());
    }

    fn create_task(id: &str, project_id: &str, content: &str) -> Task {
        crate::api::rest::Task {
            project_id: project_id.to_string(),
            ..crate::api::rest::Task::new(id, content)
        }
    }

    fn create_comment(id: &str, tid: ThreadID, content: &str) -> Comment {
        Comment {
            id: id.to_string(),
            thread: tid,
            posted_at: Utc::now(),
            content: content.to_string(),
            attachment: None,
        }
    }
}