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//! Schema-only driver for reading and writing PostgreSQL `CREATE TABLE` schema.

use lazy_static::lazy_static;
use regex::Regex;
use std::{
    fmt,
    str::{self, FromStr},
};

use crate::common::*;
use crate::drivers::postgres_shared::{PgName, PgSchema};

/// An SQL file containing a `CREATE TABLE` statement using Postgres syntax.
#[derive(Clone, Debug)]
pub struct PostgresSqlLocator {
    path: PathOrStdio,
}

impl fmt::Display for PostgresSqlLocator {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.path.fmt_locator_helper(Self::scheme(), f)
    }
}

impl FromStr for PostgresSqlLocator {
    type Err = Error;

    fn from_str(s: &str) -> Result<Self> {
        let path = PathOrStdio::from_str_locator_helper(Self::scheme(), s)?;
        Ok(PostgresSqlLocator { path })
    }
}

impl Locator for PostgresSqlLocator {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn schema(&self, ctx: Context) -> BoxFuture<Option<Schema>> {
        schema_helper(ctx, self.to_owned()).boxed()
    }

    fn write_schema(
        &self,
        ctx: Context,
        schema: Schema,
        if_exists: IfExists,
    ) -> BoxFuture<()> {
        write_schema_helper(ctx, self.to_owned(), schema, if_exists).boxed()
    }
}

impl LocatorStatic for PostgresSqlLocator {
    fn scheme() -> &'static str {
        "postgres-sql:"
    }

    fn features() -> Features {
        Features {
            locator: LocatorFeatures::Schema | LocatorFeatures::WriteSchema,
            write_schema_if_exists: IfExistsFeatures::no_append(),
            source_args: EnumSet::empty(),
            dest_args: EnumSet::empty(),
            dest_if_exists: EnumSet::empty(),
            _placeholder: (),
        }
    }
}

/// Implementation of `schema`, but as a real `async` function.
async fn schema_helper(
    _ctx: Context,
    source: PostgresSqlLocator,
) -> Result<Option<Schema>> {
    let input = source
        .path
        .open_async()
        .await
        .with_context(|_| format!("error opening {}", source.path))?;
    let sql = async_read_to_string(input)
        .await
        .with_context(|_| format!("error reading {}", source.path))?;
    let pg_schema = PgSchema::parse(source.path.to_string(), sql)?;
    let schema = pg_schema.to_schema()?;
    Ok(Some(schema))
}

/// Implementation of `write_schema`, but as a real `async` function.
async fn write_schema_helper(
    ctx: Context,
    dest: PostgresSqlLocator,
    schema: Schema,
    if_exists: IfExists,
) -> Result<()> {
    // TODO: We use the existing `table.name` here, but this might produce
    // odd results if the input table comes from BigQuery or another
    // database with a very different naming scheme.
    let table_name = sanitize_table_name(&schema.table.name)?.parse::<PgName>()?;
    let pg_schema = PgSchema::from_schema_and_name(&ctx, &schema, &table_name)?;
    let mut out = dest.path.create_async(ctx, if_exists).await?;
    buffer_sync_write_and_copy_to_async(&mut out, |buff| {
        write!(buff, "{}", pg_schema)
    })
    .await
    .with_context(|_| format!("error writing {}", dest.path))?;
    out.flush().await?;
    Ok(())
}

/// Make sure a table name is legal for PostgreSQL.
///
/// This will use an valid-looking table name if it can find one somewhere in
/// the string, or it will return a default value.
fn sanitize_table_name(table_name: &str) -> Result<String> {
    lazy_static! {
        static ref RE: Regex = Regex::new(
            r"(?x)
                ([_a-zA-Z][_a-zA-Z0-9]*\.)?
                ([_a-zA-Z][_a-zA-Z0-9]*)
            $"
        )
        .expect("could not compile regex in source");
    }
    if let Some(cap) = RE.captures(table_name) {
        Ok(cap[0].to_owned())
    } else {
        // Just use a generic table name.
        Ok("data".to_owned())
    }
}