use crate::http;

#[derive(Debug, Clone, Default)]
pub struct OEmbed {
    pub oembed_type: Option<String>,
    pub title: Option<String>,
    pub description: Option<String>,
    pub provider_name: Option<String>,
    pub provider_url: Option<String>,
    pub author_name: Option<String>,
    pub author_url: Option<String>,
    pub thumbnail_url: Option<String>,
    pub url: Option<String>,
    pub html: Option<String>,
    pub width: Option<u32>,
    pub height: Option<u32>,
}

pub async fn fetch(endpoint: &str, max_bytes: usize) -> Option<OEmbed> {
    let fetched = http::fetch(endpoint, "application/json", max_bytes)
        .await
        .ok()?;
    if !(200..300).contains(&fetched.status) {
        return None;
    }
    parse(&fetched.body)
}

pub fn parse(body: &str) -> Option<OEmbed> {
    let value: serde_json::Value = serde_json::from_str(body).ok()?;
    if !value.is_object() {
        return None;
    }
    let oembed = OEmbed {
        oembed_type: string_field(&value, "type"),
        title: string_field(&value, "title"),
        description: string_field(&value, "description"),
        provider_name: string_field(&value, "provider_name"),
        provider_url: string_field(&value, "provider_url"),
        author_name: string_field(&value, "author_name"),
        author_url: string_field(&value, "author_url"),
        thumbnail_url: string_field(&value, "thumbnail_url"),
        url: string_field(&value, "url"),
        html: string_field(&value, "html"),
        width: number_field(&value, "width"),
        height: number_field(&value, "height"),
    };
    (oembed.title.is_some()
        || oembed.description.is_some()
        || oembed.thumbnail_url.is_some()
        || oembed.html.is_some())
    .then_some(oembed)
}

fn string_field(value: &serde_json::Value, key: &str) -> Option<String> {
    let text = value.get(key)?.as_str()?.trim();
    (!text.is_empty()).then(|| text.to_owned())
}

fn number_field(value: &serde_json::Value, key: &str) -> Option<u32> {
    let node = value.get(key)?;
    node.as_u64()
        .and_then(|value| u32::try_from(value).ok())
        .or_else(|| node.as_str().and_then(|value| value.trim().parse().ok()))
}

pub fn iframe_src(html: &str) -> Option<String> {
    let lower = html.to_ascii_lowercase();
    let start = lower.find("<iframe")?;
    let tail = &html[start..];
    let index = tail.to_ascii_lowercase().find("src=")? + 4;
    let after = tail[index..].trim_start();
    let quote = after.chars().next()?;
    if quote != '"' && quote != '\'' {
        return None;
    }
    let rest = &after[1..];
    let end = rest.find(quote)?;
    let src = rest[..end].trim();
    (!src.is_empty()).then(|| src.to_owned())
}