//! PivotTables: reading the source list, grouping and aggregating, laying out the report and
//! writing it onto the sheet as static, styled cells.
//!
//! Behaviour follows Excel's documented PivotTable model (rows/columns/values/filters areas,
//! Compact/Outline/Tabular layouts, subtotals, grand totals, show-values-as); the code and the
//! look (our own palette) are original.

use std::cmp::Ordering;
use std::collections::{HashMap, HashSet};

use gridcraft_core::date::datetime_from_serial;
pub use gridcraft_core::quote_sheet;
use gridcraft_core::{CellError, CellRef, MAX_COLS, MAX_ROWS, RangeRef, Value, split_sheet};
use gridcraft_model::{
    BorderLine, BorderStyle, Cell, Chart, Color, Fill, HAlign, NumFmt, PivotDateGroup, PivotField, PivotFilter, PivotFunc, PivotLayout, PivotShowAs,
    PivotSort, PivotTable, PivotValue, Series, Style, StyleId, Workbook,
};

use crate::pivot_calc::CalcSet;

mod charts;
mod compute;
mod items;
mod output;

use charts::rebind_charts;
pub use charts::{chart_link, chart_series, clear_output, links_to, parse_chart_link};
use compute::compute_from;
pub use compute::{NOT_A_VALUE_CELL, detail_cells, detail_records};
pub use items::{distinct_labels, func_caption, item_label};
#[cfg(test)]
use output::data_cols_exceed_sheet;
pub use output::{CellKind, OutCell, Output, RowKind};
use output::{cell_style, look};

/// Largest source block read (cells).
pub const MAX_SOURCE_CELLS: u64 = 10_000_000;
/// Largest report written (cells).
pub const MAX_OUTPUT_CELLS: u64 = 2_000_000;
/// Most fields in the Rows plus Columns areas.
pub const MAX_AXIS_FIELDS: usize = 32;
/// Most fields in the Values area.
pub const MAX_VALUE_FIELDS: usize = 256;

const MONTHS: [&str; 12] = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];

// ---------------------------------------------------------------- source

/// The source list: header names, per-column number formats and the records.
#[derive(Clone, Debug)]
pub struct Source {
    pub sheet: usize,
    pub range: RangeRef,
    pub headers: Vec<String>,
    pub formats: Vec<String>,
    /// Every non-blank value in the column is a number.
    pub numeric: Vec<bool>,
    /// Numeric with a date number format.
    pub dates: Vec<bool>,
    pub rows: Vec<Vec<Value>>,
}

impl Source {
    pub fn col(&self, name: &str) -> Option<usize> {
        self.headers.iter().position(|h| h.eq_ignore_ascii_case(name))
    }
}

/// Absolute reference text for a range on a sheet: `Sheet1!$A$1:$E$20`.
pub fn range_text(sheet_name: &str, r: RangeRef) -> String {
    let abs = |c: CellRef| format!("${}${}", gridcraft_core::col_to_letters(c.col), c.row as u64 + 1);
    format!("{}!{}:{}", quote_sheet(sheet_name), abs(r.start), abs(r.end))
}

/// Resolves source text (range, table name or defined name) to (sheet, range including header).
pub fn resolve_source(wb: &Workbook, text: &str, default_sheet: usize) -> Result<(usize, RangeRef), String> {
    resolve_inner(wb, text, default_sheet, 0)
}

fn resolve_inner(wb: &Workbook, text: &str, default_sheet: usize, depth: u32) -> Result<(usize, RangeRef), String> {
    const INVALID: &str = "The reference isn't valid.";
    let t = text.trim().trim_start_matches('=').trim();
    if t.is_empty() || depth > 4 {
        return Err(INVALID.into());
    }
    if let Some((si, ti)) = wb.table(t)
        && let Some(tb) = wb.sheet(si).and_then(|s| s.tables.get(ti))
    {
        if !tb.header_row {
            return Err("The table needs a header row to be used as a PivotTable source.".into());
        }
        let end_row = tb.range.end.row.saturating_sub(tb.totals_row as u32).max(tb.range.start.row);
        return Ok((si, RangeRef::new(tb.range.start, CellRef::new(end_row, tb.range.end.col))));
    }
    let (sheet, body) = split_sheet(t);
    if let Some(r) = RangeRef::parse(body) {
        let si = match sheet {
            Some(n) => wb.sheet_index(&n).ok_or_else(|| INVALID.to_string())?,
            None => default_sheet,
        };
        let sh = wb.sheet(si).ok_or_else(|| INVALID.to_string())?;
        let r = if r.is_full_cols() || r.is_full_rows() {
            let used = sh.used_range().ok_or_else(|| INVALID.to_string())?;
            r.intersection(&used).ok_or_else(|| INVALID.to_string())?
        } else {
            r
        };
        return Ok((si, r));
    }
    if sheet.is_none()
        && let Some(n) = wb.name(t, default_sheet)
    {
        let f = n.formula.clone();
        return resolve_inner(wb, &f, default_sheet, depth + 1);
    }
    Err(INVALID.into())
}

const FIELD_NAME_ERR: &str =
    "The PivotTable field name is not valid. To create a PivotTable, you must use data that is organized as a list with labeled columns.";

/// Reads the source list.
pub fn read_source(wb: &Workbook, text: &str, default_sheet: usize) -> Result<Source, String> {
    let (si, r) = resolve_source(wb, text, default_sheet)?;
    let sh = wb.sheet(si).ok_or("The reference isn't valid.")?;
    if r.count() > MAX_SOURCE_CELLS {
        return Err("The source range is too large for a PivotTable.".into());
    }
    let mut headers: Vec<String> = Vec::new();
    // Names taken so far (lower-case), and the next suffix to try for each repeated header, so
    // that thousands of equal headers don't take cubic time.
    let mut taken: HashSet<String> = HashSet::new();
    let mut next_suffix: HashMap<String, usize> = HashMap::new();
    let mut formats = Vec::new();
    for c in r.start.col..=r.end.col {
        let h = crate::display::cell_text(wb, sh, CellRef::new(r.start.row, c)).trim().to_string();
        if h.is_empty() {
            return Err(FIELD_NAME_ERR.into());
        }
        let key = h.to_ascii_lowercase();
        let mut n = h.clone();
        let mut k = next_suffix.get(&key).copied().unwrap_or(2);
        while taken.contains(&n.to_ascii_lowercase()) {
            n = format!("{h}{k}");
            k += 1;
        }
        next_suffix.insert(key, k);
        taken.insert(n.to_ascii_lowercase());
        headers.push(n);
        let fmt = if r.end.row > r.start.row {
            wb.styles.get(sh.style_id(CellRef::new(r.start.row + 1, c))).num_fmt.as_str().to_string()
        } else {
            "General".into()
        };
        formats.push(fmt);
    }
    let w = headers.len();
    let mut rows = Vec::new();
    let mut numeric = vec![true; w];
    let mut any = vec![false; w];
    if r.end.row > r.start.row {
        for row in r.start.row + 1..=r.end.row {
            let rec: Vec<Value> = (r.start.col..=r.end.col).map(|c| sh.value(CellRef::new(row, c)).scalar()).collect();
            if rec.iter().all(Value::is_empty) {
                continue;
            }
            for (i, v) in rec.iter().enumerate() {
                if !v.is_empty() {
                    if let Some(a) = any.get_mut(i) {
                        *a = true;
                    }
                    if !v.is_number()
                        && let Some(n) = numeric.get_mut(i)
                    {
                        *n = false;
                    }
                }
            }
            rows.push(rec);
        }
    }
    for (n, a) in numeric.iter_mut().zip(any.iter()) {
        *n = *n && *a;
    }
    let dates = numeric.iter().zip(formats.iter()).map(|(n, f)| *n && crate::display::number_format(f).is_date()).collect();
    Ok(Source { sheet: si, range: r, headers, formats, numeric, dates, rows })
}

/// Computes a PivotTable report from the workbook.
pub fn compute(wb: &Workbook, pt: &PivotTable, pivot_sheet: usize) -> Result<Output, String> {
    let src = read_source(wb, &pt.source, pivot_sheet)?;
    compute_from(wb, pt, &src, None)
}

/// Recomputes a pivot and writes its report. With `replace` false, refuses when the target area
/// holds other data. Returns the written area.
pub fn refresh(wb: &mut Workbook, sheet: usize, idx: usize, replace: bool) -> Result<RangeRef, String> {
    let pt = wb.sheet(sheet).and_then(|s| s.pivots.get(idx)).cloned().ok_or("There's no such PivotTable.")?;
    let out = compute(wb, &pt, sheet)?;
    let h = out.height().max(1);
    let w = out.width.max(1);
    let k = out.body_offset;
    let origin_row = if pt.anchor.row >= k { pt.anchor.row - k } else { pt.anchor.row };
    let origin = CellRef::new(origin_row, pt.anchor.col);
    let end_row = origin.row as u64 + h as u64 - 1;
    let end_col = origin.col as u64 + w as u64 - 1;
    if end_row >= MAX_ROWS as u64 || end_col >= MAX_COLS as u64 {
        return Err("The PivotTable report will not fit on the sheet. Choose a different location.".into());
    }
    let area = RangeRef::new(origin, CellRef::new(end_row as u32, end_col as u32));
    let sh = wb.sheet(sheet).ok_or("There's no such sheet.")?;
    for (j, other) in sh.pivots.iter().enumerate() {
        if j != idx && other.last_range.is_some_and(|r| r.intersects(&area)) {
            return Err("A PivotTable report cannot overlap another PivotTable report.".into());
        }
    }
    if sh.is_protected() {
        return Err("The cell or chart you're trying to change is on a protected sheet.".into());
    }
    if let Ok((ssi, sr)) = resolve_source(wb, &pt.source, sheet)
        && ssi == sheet
        && sr.intersects(&area)
    {
        return Err("The PivotTable report can't overlap its source data. Choose a different location.".into());
    }
    if sh.tables.iter().any(|t| t.range.intersects(&area)) {
        return Err("A PivotTable report cannot overlap a table.".into());
    }
    if !replace {
        for (c, cell) in sh.cells.iter_range(area) {
            if cell.has_content() && !pt.last_range.is_some_and(|r| r.contains(c)) {
                return Err(format!(
                    "There's already data in {}!{}. Do you want to replace it? (Run again with replace: true to overwrite.)",
                    quote_sheet(&sh.name),
                    c.a1()
                ));
            }
        }
        if let Some(c) = sh.spill.keys().find(|c| area.contains(**c) && !pt.last_range.is_some_and(|r| r.contains(**c))) {
            return Err(format!(
                "There's already data in {}!{}. Do you want to replace it? (Run again with replace: true to overwrite.)",
                quote_sheet(&sh.name),
                c.a1()
            ));
        }
    }
    // Styles first (the style table is workbook-wide).
    let lk = look(&pt.style);
    let header_last = out.row_kinds.iter().rposition(|k| *k == RowKind::Header);
    let mut cache: HashMap<Style, StyleId> = HashMap::new();
    let mut cells: Vec<(CellRef, Cell)> = Vec::new();
    for (ri, row) in out.grid.iter().enumerate() {
        let rk = out.row_kinds.get(ri).copied().unwrap_or(RowKind::Blank);
        if rk == RowKind::Blank {
            continue;
        }
        for (ci, oc) in row.iter().enumerate() {
            if rk == RowKind::Filter && oc.value.is_empty() {
                continue;
            }
            if rk == RowKind::Placeholder && oc.value.is_empty() {
                continue;
            }
            let flag = match rk {
                RowKind::Header => Some(ri) == header_last,
                RowKind::Filter => ci == 0,
                _ => false,
            };
            let st = cell_style(&lk, rk, oc, flag);
            let id = match cache.get(&st) {
                Some(id) => *id,
                None => {
                    let id = wb.styles.intern(st.clone());
                    cache.insert(st, id);
                    id
                }
            };
            if oc.value.is_empty() && id == StyleId::default() {
                continue;
            }
            cells.push((
                CellRef::new(origin.row + ri as u32, origin.col + ci as u32),
                Cell { value: oc.value.clone(), formula: None, style: id, py: None },
            ));
        }
    }
    // Column widths that fit the labels.
    let mut widths: HashMap<u32, f32> = HashMap::new();
    for (c, cell) in &cells {
        if cell.value.is_empty() {
            continue;
        }
        let st = wb.styles.get(cell.style);
        let text = crate::display::format(&cell.value, st.num_fmt.as_str(), wb).text;
        let wpt = crate::cmd::format::approx_text_width(&text, st.font.size, st.font.bold) + st.align.indent as f32 * 9.0 + 14.0;
        let e = widths.entry(c.col).or_insert(0.0);
        *e = e.max(wpt.min(320.0));
    }
    let shm = wb.sheet_mut(sheet).ok_or("There's no such sheet.")?;
    if let Some(old) = pt.last_range {
        shm.take_cells(old);
    }
    shm.take_cells(area);
    for (c, cell) in cells {
        shm.set_cell(c, cell);
    }
    for (col, wpt) in widths {
        if wpt > shm.col_width(col) && !shm.is_col_hidden(col) {
            shm.cols.entry(col).or_default().size = Some(wpt);
        }
    }
    if let Some(p) = shm.pivots.get_mut(idx) {
        p.last_range = Some(area);
    }
    let sheet_name = shm.name.clone();
    rebind_charts(wb, &sheet_name, &pt.name, origin, &out);
    Ok(area)
}

#[cfg(test)]
mod fit_tests {
    use super::data_cols_exceed_sheet;

    #[test]
    fn column_budget_counts_value_fields_and_grand_total() {
        assert!(!data_cols_exceed_sheet(64, true, 128));
        assert!(data_cols_exceed_sheet(64, true, 256));
        assert!(!data_cols_exceed_sheet(64, false, 256));
        assert!(!data_cols_exceed_sheet(16_384, false, 0));
        assert!(data_cols_exceed_sheet(16_385, false, 0));
    }
}