//! LastPass CSV importer.
//!
//! Pure: takes CSV bytes, returns a vector of `Item` (with freshly-minted
//! IDs and timestamps) plus a vector of `ImportWarning` for skipped or
//! partially-imported rows. Failed rows never abort the whole import;
//! the only fatal error is a missing or malformed header.
//!
//! Spec: docs/superpowers/specs/2026-04-27-relicario-import-export-design.md
//! (D10–D13 + the LastPass field-mapping table).

use serde::{Deserialize, Serialize};
use url::Url;
use zeroize::Zeroizing;

use crate::error::{RelicarioError, Result};
use crate::item::Item;
use crate::item_types::{ItemCore, LoginCore};

/// LastPass column order. The header row must contain these exact column
/// names in this exact order.
pub const EXPECTED_HEADER: &[&str] =
    &["url", "username", "password", "totp", "extra", "name", "grouping", "fav"];

/// A row that was skipped, or partially imported with a downgrade
/// (e.g., login imported without TOTP).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ImportWarning {
    /// 1-indexed row number in the CSV body (the header is row 0).
    pub row: usize,
    /// Title from the row's `name` column, if present and non-empty.
    pub title: Option<String>,
    /// Human-readable explanation, suitable for stderr / inline UI.
    pub message: String,
}

/// Parse a LastPass CSV export.
///
/// Returns the parsed items (with fresh IDs and timestamps) and any
/// per-row warnings. The function only fails if the header is missing
/// or doesn't match `EXPECTED_HEADER`.
pub fn parse_lastpass_csv(csv_bytes: &[u8]) -> Result<(Vec<Item>, Vec<ImportWarning>)> {
    let mut reader = csv::ReaderBuilder::new()
        .has_headers(true)
        .flexible(false)
        .from_reader(csv_bytes);

    // Validate header.
    let headers = reader
        .headers()
        .map_err(|e| RelicarioError::ImportCsvFormat(format!("read header: {e}")))?
        .clone();
    if headers.len() != EXPECTED_HEADER.len()
        || headers.iter().zip(EXPECTED_HEADER).any(|(got, want)| got != *want)
    {
        return Err(RelicarioError::ImportCsvHeader(format!(
            "expected `{}`, got `{}`",
            EXPECTED_HEADER.join(","),
            headers.iter().collect::<Vec<_>>().join(",")
        )));
    }

    let mut items = Vec::new();
    let mut warnings = Vec::new();

    for (idx, record) in reader.records().enumerate() {
        let row_num = idx + 1;
        let record = match record {
            Ok(r) => r,
            Err(e) => {
                warnings.push(ImportWarning {
                    row: row_num,
                    title: None,
                    message: format!("CSV parse error — skipped: {e}"),
                });
                continue;
            }
        };

        match map_row(&record, row_num) {
            Ok(item) => items.push(item),
            Err(w) => warnings.push(w),
        }
    }

    Ok((items, warnings))
}

/// Map a single CSV record to either an `Item` or an `ImportWarning`.
/// Column order is fixed by `EXPECTED_HEADER`.
fn map_row(record: &csv::StringRecord, row: usize) -> std::result::Result<Item, ImportWarning> {
    let url      = record.get(0).unwrap_or("").trim();
    let username = record.get(1).unwrap_or("").trim();
    let password = record.get(2).unwrap_or("");
    let _totp    = record.get(3).unwrap_or(""); // populated in Task 4
    let extra    = record.get(4).unwrap_or("");
    let name     = record.get(5).unwrap_or("").trim();
    let group    = record.get(6).unwrap_or("").trim();
    let fav      = record.get(7).unwrap_or("").trim();

    if name.is_empty() {
        return Err(ImportWarning {
            row,
            title: None,
            message: "missing `name` — skipped".into(),
        });
    }

    if password.is_empty() {
        return Err(ImportWarning {
            row,
            title: Some(name.to_string()),
            message: "missing `password` — skipped".into(),
        });
    }

    let parsed_url = if url.is_empty() { None } else { Url::parse(url).ok() };

    let mut item = Item::new(
        name.to_string(),
        ItemCore::Login(LoginCore {
            username: if username.is_empty() { None } else { Some(username.to_string()) },
            password: Some(Zeroizing::new(password.to_string())),
            url: parsed_url,
            totp: None,
        }),
    );
    item.group    = if group.is_empty() { None } else { Some(group.to_string()) };
    item.favorite = fav == "1";
    item.notes    = if extra.is_empty() { None } else { Some(extra.to_string()) };
    Ok(item)
}