//! Authors module. Owns the read/write paths for the persona layer.
//!
//! An [`Author`] is the immutable identity (slug, display_name, model).
//! A [`Revision`] is the versioned soul content — exactly one revision
//! per author is marked `is_current = true` at any time.
//!
//! When skald-the-binary runs a forge pass, it pulls the current
//! revision via [`get_with_current_revision`], stuffs the soul into
//! the system prompt with `SystemMode::Replace`, and the model
//! becomes the author for the duration of the call.

use anyhow::{Context, bail};
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use sqlx::PgPool;
use uuid::Uuid;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Author {
    pub id: Uuid,
    pub slug: String,
    pub display_name: String,
    pub persona_tagline: Option<String>,
    pub model: String,
    pub is_synthetic: bool,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Revision {
    pub id: Uuid,
    pub author_id: Uuid,
    pub n: i32,
    pub soul: String,
    pub system_template: Option<String>,
    pub tools: Vec<String>,
    pub note: Option<String>,
    pub is_current: bool,
    pub created_at: DateTime<Utc>,
}

/// An author + their currently-active revision. Most pipeline calls
/// want both at once.
#[derive(Debug, Clone)]
pub struct AuthorWithRevision {
    pub author: Author,
    pub revision: Revision,
}

/// Fetch an author by slug. Returns None if no such author.
pub async fn get_by_slug(pool: &PgPool, slug: &str) -> anyhow::Result<Option<Author>> {
    let row: Option<(Uuid, String, String, Option<String>, String, bool, DateTime<Utc>, DateTime<Utc>)> =
        sqlx::query_as(
            "SELECT id, slug, display_name, persona_tagline, model, is_synthetic,
                    created_at, updated_at
             FROM authors WHERE slug = $1",
        )
        .bind(slug)
        .fetch_optional(pool)
        .await?;
    Ok(row.map(
        |(id, slug, display_name, persona_tagline, model, is_synthetic, created_at, updated_at)| {
            Author {
                id,
                slug,
                display_name,
                persona_tagline,
                model,
                is_synthetic,
                created_at,
                updated_at,
            }
        },
    ))
}

/// Fetch an author + their current revision in one call.
pub async fn get_with_current_revision(
    pool: &PgPool,
    slug: &str,
) -> anyhow::Result<Option<AuthorWithRevision>> {
    let Some(author) = get_by_slug(pool, slug).await? else {
        return Ok(None);
    };
    let revision = get_current_revision(pool, author.id)
        .await?
        .with_context(|| format!("author {slug} has no current revision"))?;
    Ok(Some(AuthorWithRevision { author, revision }))
}

/// Fetch the current revision for an author.
pub async fn get_current_revision(
    pool: &PgPool,
    author_id: Uuid,
) -> anyhow::Result<Option<Revision>> {
    let row: Option<(Uuid, Uuid, i32, String, Option<String>, Vec<String>, Option<String>, bool, DateTime<Utc>)> =
        sqlx::query_as(
            "SELECT id, author_id, n, soul, system_template, tools, note, is_current, created_at
             FROM author_revisions WHERE author_id = $1 AND is_current = true",
        )
        .bind(author_id)
        .fetch_optional(pool)
        .await?;
    Ok(row.map(|(id, author_id, n, soul, system_template, tools, note, is_current, created_at)| {
        Revision {
            id,
            author_id,
            n,
            soul,
            system_template,
            tools,
            note,
            is_current,
            created_at,
        }
    }))
}

/// Fetch a specific revision by id (e.g. the one pinned on a story).
pub async fn get_revision(pool: &PgPool, revision_id: Uuid) -> anyhow::Result<Option<Revision>> {
    let row: Option<(Uuid, Uuid, i32, String, Option<String>, Vec<String>, Option<String>, bool, DateTime<Utc>)> =
        sqlx::query_as(
            "SELECT id, author_id, n, soul, system_template, tools, note, is_current, created_at
             FROM author_revisions WHERE id = $1",
        )
        .bind(revision_id)
        .fetch_optional(pool)
        .await?;
    Ok(row.map(|(id, author_id, n, soul, system_template, tools, note, is_current, created_at)| {
        Revision {
            id,
            author_id,
            n,
            soul,
            system_template,
            tools,
            note,
            is_current,
            created_at,
        }
    }))
}

/// Create a new author. Idempotent on slug — if an author with this
/// slug exists, returns it instead.
pub async fn create_or_get(
    pool: &PgPool,
    slug: &str,
    display_name: &str,
    persona_tagline: Option<&str>,
) -> anyhow::Result<Author> {
    if let Some(existing) = get_by_slug(pool, slug).await? {
        return Ok(existing);
    }
    sqlx::query(
        "INSERT INTO authors (slug, display_name, persona_tagline)
         VALUES ($1, $2, $3)",
    )
    .bind(slug)
    .bind(display_name)
    .bind(persona_tagline)
    .execute(pool)
    .await?;
    get_by_slug(pool, slug)
        .await?
        .with_context(|| format!("author {slug} just created but not found"))
}

/// Add a new revision to an author and mark it current. The previous
/// current revision (if any) gets flipped to is_current=false.
pub async fn add_revision(
    pool: &PgPool,
    author_id: Uuid,
    soul: &str,
    system_template: Option<&str>,
    tools: &[String],
    note: Option<&str>,
) -> anyhow::Result<Revision> {
    let mut tx = pool.begin().await?;

    // Demote the current revision if there is one.
    sqlx::query("UPDATE author_revisions SET is_current = false WHERE author_id = $1 AND is_current = true")
        .bind(author_id)
        .execute(&mut *tx)
        .await?;

    // Next n.
    let next_n: i32 = sqlx::query_scalar(
        "SELECT COALESCE(MAX(n), 0) + 1 FROM author_revisions WHERE author_id = $1",
    )
    .bind(author_id)
    .fetch_one(&mut *tx)
    .await?;

    let revision_id: Uuid = sqlx::query_scalar(
        "INSERT INTO author_revisions
            (author_id, n, soul, system_template, tools, note, is_current)
         VALUES ($1, $2, $3, $4, $5, $6, true)
         RETURNING id",
    )
    .bind(author_id)
    .bind(next_n)
    .bind(soul)
    .bind(system_template)
    .bind(tools)
    .bind(note)
    .fetch_one(&mut *tx)
    .await?;

    tx.commit().await?;

    get_revision(pool, revision_id)
        .await?
        .with_context(|| format!("revision {revision_id} just inserted but not found"))
}

/// Assign an author + revision to an existing story. Pins the
/// revision so future re-reads always know which version wrote
/// what. Also adds a row to author_corpus marking the author as
/// having authored this story.
pub async fn assign_to_story(
    pool: &PgPool,
    story_id: Uuid,
    author_id: Uuid,
    revision_id: Uuid,
) -> anyhow::Result<()> {
    let mut tx = pool.begin().await?;

    let affected = sqlx::query(
        "UPDATE stories
         SET author_id = $1, author_revision_id = $2
         WHERE id = $3",
    )
    .bind(author_id)
    .bind(revision_id)
    .bind(story_id)
    .execute(&mut *tx)
    .await?;
    if affected.rows_affected() == 0 {
        bail!("story {story_id} not found");
    }

    sqlx::query(
        "INSERT INTO author_corpus (author_id, story_id, role)
         VALUES ($1, $2, 'authored')
         ON CONFLICT (author_id, story_id) DO NOTHING",
    )
    .bind(author_id)
    .bind(story_id)
    .execute(&mut *tx)
    .await?;

    tx.commit().await?;
    Ok(())
}

#[cfg(test)]
mod tests {
    // DB-touching tests live in skald/tests/integration.rs against a
    // real ephemeral postgres. Unit tests would mostly check trivial
    // mappings.
}