use std::str;

use chrono_tz::Tz;
use scraper::{ElementRef, Html, Selector};
use serde::{de, Deserialize, Deserializer, Serialize};
use tinytemplate::TinyTemplate;

use crate::entry::{self, Date, Entry};
use crate::probe::Probe;

#[derive(Serialize)]
struct Context {
    number: String,
}

#[derive(Debug, Deserialize)]
pub struct Definition {
    name: String,
    path: String,
    messages: Vec<Field>,
    #[serde(default)]
    history: Vec<Field>,
    #[serde(default)]
    comments: Vec<Comment>,
}

#[derive(Debug, Deserialize)]
struct Comment {
    #[serde(deserialize_with = "deserialize_selector")]
    selector: Selector,
    #[serde(rename = "date_time")]
    datetime: Option<DateTime>,
    title: Option<Field>,
    message: Option<Field>,
}

#[derive(Debug, Deserialize)]
#[serde(rename_all = "snake_case")]
struct DateTime {
    #[serde(flatten)]
    field: Field,
    kind: DateTimeKind,
    format: String,
    #[serde(deserialize_with = "deserialize_tz")]
    tz: Tz,
}

#[derive(Debug, Deserialize)]
#[serde(rename_all = "snake_case")]
enum DateTimeKind {
    Date,
    DateTime,
}

#[derive(Debug, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum Filter {}

#[derive(Debug, Deserialize)]
struct Field {
    #[serde(deserialize_with = "deserialize_selector")]
    selector: Selector,
    #[serde(default)]
    data: Data,
    #[serde(default)]
    filters: Vec<Filter>,
}

#[derive(Debug)]
enum Data {
    Text,
    InnerHtml,
    Attr { attr: String },
}

impl Data {
    fn extract(&self, element: &ElementRef) -> Option<String> {
        match self {
            Data::Text => Some(
                element
                    .text()
                    .map(str::trim)
                    .filter(|s| !s.is_empty())
                    .collect::<Vec<_>>()
                    .join(" "),
            ),
            Data::InnerHtml => Some(element.inner_html()),
            Data::Attr { attr } => element.value().attr(attr).map(|data| data.to_string()),
        }
    }
}

impl Default for Data {
    fn default() -> Self {
        Data::Text
    }
}

impl<'de> Deserialize<'de> for Data {
    fn deserialize<D>(deserializer: D) -> Result<Data, D::Error>
    where
        D: Deserializer<'de>,
    {
        use std::fmt;

        use serde::de::{self, Visitor};

        struct StrVisitor;

        impl<'de> Visitor<'de> for StrVisitor {
            type Value = Data;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("an str")
            }

            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
            where
                E: de::Error,
            {
                match value {
                    "text" => Ok(Data::Text),
                    "inner_html" => Ok(Data::InnerHtml),
                    s if s.starts_with("attr:") => {
                        let attr = s.splitn(2, ":").nth(1).unwrap();

                        Ok(Data::Attr {
                            attr: attr.to_string(),
                        })
                    }
                    _ => Err(E::custom(format!("unknown data type: {}", value))),
                }
            }
        }

        deserializer.deserialize_str(StrVisitor)
    }
}

impl Probe for Definition {
    fn provider(&self) -> &str {
        &self.name
    }

    fn uri(&self, number: &str) -> String {
        let mut tt = TinyTemplate::new();

        tt.add_template("path", &self.path)
            .expect("failed to add path template");

        let context = Context {
            number: number.to_string(),
        };

        tt.render("path", &context)
            .expect("failed to render path template")
    }

    fn fetch(&self, number: &str) -> Result<String, ()> {
        reqwest::get(&self.uri(number))
            .map_err(|_| ())?
            .text()
            .map_err(|_| ())
    }

    fn parse(&self, data: &str) -> Result<Entry, ()> {
        let html = Html::parse_document(data);

        let mut messages = Vec::new();
        let mut history = Vec::new();
        let mut comments = Vec::new();

        for field in &self.messages {
            for element in html.select(&field.selector) {
                if let Some(data) = field.data.extract(&element) {
                    messages.push(data);
                }
            }
        }

        for field in &self.history {
            for element in html.select(&field.selector) {
                if let Some(data) = field.data.extract(&element) {
                    history.push(data);
                }
            }
        }

        for comment in &self.comments {
            for comments_element in html.select(&comment.selector) {
                let mut datetime: Option<Date> = None;
                let mut title: Option<String> = None;
                let mut message: Option<String> = None;

                if let Some(ref datetime_field) = comment.datetime {
                    for comment_element in comments_element.select(&datetime_field.field.selector) {
                        if let Some(data) = datetime_field.field.data.extract(&comment_element) {
                            // for filter in &datetime_field.field.filters {}

                            let data = match datetime_field.kind {
                                DateTimeKind::Date => Date::date_from(
                                    datetime_field.tz,
                                    &data,
                                    &datetime_field.format,
                                )
                                .expect("failed to parse date"),
                                DateTimeKind::DateTime => Date::datetime_from(
                                    datetime_field.tz,
                                    &data,
                                    &datetime_field.format,
                                )
                                .expect("failed to parse date time"),
                            };

                            datetime = Some(data);
                        }
                    }
                }

                if let Some(ref title_field) = comment.title {
                    for comment_element in comments_element.select(&title_field.selector) {
                        if let Some(data) = title_field
                            .data
                            .extract(&comment_element)
                            .filter(|data| !data.is_empty())
                        {
                            // for filter in &message_field.filters {}

                            title = Some(data);
                        }
                    }
                }

                if let Some(ref message_field) = comment.message {
                    for comment_element in comments_element.select(&message_field.selector) {
                        if let Some(data) = message_field.data.extract(&comment_element) {
                            // for filter in &message_field.filters {}

                            message = Some(data);
                        }
                    }
                }

                if datetime.is_some() && message.is_some() {
                    comments.push(entry::Comment {
                        datetime: datetime.unwrap(),
                        title,
                        message: message.unwrap(),
                    });
                }
            }
        }

        if !messages.is_empty() || !history.is_empty() || !comments.is_empty() {
            Ok(Entry {
                messages,
                history,
                comments,
            })
        } else {
            Err(())
        }
    }
}

fn deserialize_selector<'de, D>(deserializer: D) -> Result<Selector, D::Error>
where
    D: Deserializer<'de>,
{
    let s = String::deserialize(deserializer)?;

    Selector::parse(&s).map_err(|_| de::Error::custom("failed to parse selector"))
}

fn deserialize_tz<'de, D>(deserializer: D) -> Result<Tz, D::Error>
where
    D: Deserializer<'de>,
{
    let s = String::deserialize(deserializer)?;

    s.parse::<Tz>()
        .map_err(|_| de::Error::custom("failed to parse tz"))
}