// Copyright 2026 Alibaba Group
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package output

import (
	"encoding/csv"
	"io"
)

var writeCSVRecord = (*csv.Writer).Write

// writeCSV renders a payload as RFC-4180 CSV.
//
// It mirrors the shape decisions `-f table` already makes (same helpers:
// normalizePayload / unwrapPrimaryObject / extractRowsFromMap / rowsFromSlice /
// formatValue), so column order and value flattening stay consistent between
// the two formats:
//
//   - a list of objects — either a bare [{...},...] or wrapped under a
//     well-known key ({items|results|data|records|...}) — becomes a header row
//     plus one row per element. The union of keys (sorted) is the column set;
//     missing values are empty cells; nested objects/arrays render as compact
//     JSON in the cell. Any sibling metadata of the list (total, hasMore, ...)
//     is broadcast as extra trailing columns, repeated on every row, so a CSV
//     consumer never loses it (CSV has no "two tables in one file" concept the
//     way the table renderer's footer does). Meta keys that collide with a data
//     column are skipped. An empty list still emits the header plus one row of
//     empty data cells carrying just the meta values.
//   - a single object becomes a two-column `key,value` CSV.
//   - a non-uniform list or a scalar becomes a single-column `value` CSV.
//
// `--fields` projection composes for free: WriteFiltered applies SelectFields
// before Write reaches us, so the rows are already narrowed.
//
// encoding/csv.Writer handles quoting/escaping of commas, double quotes and
// embedded newlines; cell text goes through formatValue (which also strips
// terminal control sequences, same as the table renderer).
func writeCSV(w io.Writer, payload any) error {
	normalized, err := normalizePayload(payload)
	if err != nil {
		return err
	}

	cw := csv.NewWriter(w)

	switch typed := normalized.(type) {
	case map[string]any:
		// Try table extraction first so wrappers around list payloads
		// (e.g. {result: {todoCards: [...]}}) render as a real table
		// instead of being peeled by unwrapPrimaryObject and degraded
		// to key/value rows. unwrapPrimaryObject is then the fallback
		// for single-object wrappers like {invocation: {...}}.
		if headers, rows, meta, ok := extractRowsFromMap(typed); ok {
			headers, rows = broadcastMeta(headers, rows, meta)
			return writeTableCSV(cw, headers, rows)
		}
		if inner, ok := unwrapPrimaryObject(typed); ok {
			return writeKeyValueCSV(cw, inner)
		}
		return writeKeyValueCSV(cw, typed)
	case []any:
		headers, rows := rowsFromSlice(typed)
		return writeTableCSV(cw, headers, rows)
	case nil:
		// Nothing to write — emit an empty document rather than erroring.
		cw.Flush()
		return cw.Error()
	default:
		// Scalar: a single-cell, single-row CSV.
		if err := writeCSVRecord(cw, []string{formatValue(normalized)}); err != nil {
			return err
		}
		cw.Flush()
		return cw.Error()
	}
}

func writeTableCSV(cw *csv.Writer, headers []string, rows [][]string) error {
	if err := writeCSVRecord(cw, headers); err != nil {
		return err
	}
	for _, row := range rows {
		// rowsFromSlice / extractRowsFromMap already guarantee
		// len(row) == len(headers), but stay defensive against future callers.
		if len(row) != len(headers) {
			padded := make([]string, len(headers))
			copy(padded, row)
			row = padded
		}
		if err := writeCSVRecord(cw, row); err != nil {
			return err
		}
	}
	cw.Flush()
	return cw.Error()
}

// broadcastMeta appends the list's sibling metadata (total, hasMore, ...) as
// trailing columns repeated on every row. Meta keys that collide with an
// existing data column are skipped. If there are no rows but there is meta, a
// single row of empty data cells is emitted so the meta values aren't lost.
func broadcastMeta(headers []string, rows [][]string, meta map[string]any) ([]string, [][]string) {
	if len(meta) == 0 {
		return headers, rows
	}
	existing := make(map[string]bool, len(headers))
	for _, h := range headers {
		existing[h] = true
	}
	var metaKeys []string
	var metaVals []string
	for _, k := range sortedMapKeys(meta) {
		if existing[k] {
			continue
		}
		metaKeys = append(metaKeys, k)
		metaVals = append(metaVals, formatValue(meta[k]))
	}
	if len(metaKeys) == 0 {
		return headers, rows
	}

	outHeaders := append(append([]string{}, headers...), metaKeys...)
	if len(rows) == 0 {
		emptyData := make([]string, len(headers))
		return outHeaders, [][]string{append(emptyData, metaVals...)}
	}
	outRows := make([][]string, len(rows))
	for i, r := range rows {
		nr := make([]string, 0, len(outHeaders))
		nr = append(nr, r...)
		nr = append(nr, metaVals...)
		outRows[i] = nr
	}
	return outHeaders, outRows
}

func writeKeyValueCSV(cw *csv.Writer, m map[string]any) error {
	if err := writeCSVRecord(cw, []string{"key", "value"}); err != nil {
		return err
	}
	for _, key := range sortedMapKeys(m) {
		if err := writeCSVRecord(cw, []string{key, formatValue(m[key])}); err != nil {
			return err
		}
	}
	cw.Flush()
	return cw.Error()
}