package eusupply

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"strings"

	"golang.org/x/net/html"
)

// ErrNoDetails means a tender's page had none of the labelled fields the
// public page always has: the page has changed, or isn't a tender's.
var ErrNoDetails = errors.New("eusupply: no tender details on the page")

// Details reads tender's own page and fills in its description, contract
// type, CPV codes, buyer address and number of lots, and sets HasDetails.
func (c *Client) Details(ctx context.Context, tender *Tender) error {
	body, err := c.get(ctx, tenderPath(tender.PID))
	if err != nil {
		return fmt.Errorf("reading tender %s: %w", tender.ID, err)
	}

	if err := parseDetails(body, tender); err != nil {
		return fmt.Errorf("reading tender %s: %w", tender.ID, err)
	}

	return nil
}

// parseDetails reads a tender's page into tender. Each field is a
// "ctm-content-label" div ("CPV codes:") followed by a <p> holding its
// value.
func parseDetails(body []byte, tender *Tender) error {
	document, err := html.Parse(bytes.NewReader(body))
	if err != nil {
		return err
	}

	values := make(map[string]*html.Node)
	labels := findAll(document, hasClass("div", "ctm-content-label"))
	for _, label := range labels {
		value := nextElement(label)
		if value == nil || value.Data != "p" {
			continue
		}
		name := strings.TrimSuffix(text(label), ":")
		if _, found := values[name]; !found {
			values[name] = value
		}
	}
	if len(values) == 0 {
		return ErrNoDetails
	}

	if value := values["Detailed description"]; value != nil {
		tender.Description = strings.TrimSpace(rawText(value))
	}
	if value := values["Type of contract"]; value != nil {
		tender.ContractType = text(value)
	}
	if value := values["CPV codes"]; value != nil {
		tender.CPVCodes = parseCPVCodes(value)
	}
	if value := values["Buyer"]; value != nil {
		tender.BuyerAddress = buyerAddress(value)
	}
	if deadline := values["Response deadline (UK time)"]; deadline != nil &&
		tender.Deadline == nil {
		if parsed, err := parseUKTime(text(deadline)); err == nil {
			tender.Deadline = &parsed
		}
	}
	tender.Lots = len(findAll(document, hasClass("div", "package-container")))
	tender.HasDetails = true

	return nil
}

// parseCPVCodes reads the CPV codes listed in value, one per <span>: the
// code, two non-breaking spaces, then its description.
func parseCPVCodes(value *html.Node) []CPVCode {
	var codes []CPVCode
	for _, span := range findAll(value, isTag("span")) {
		code, description, _ := strings.Cut(text(span), " ")
		if code == "" {
			continue
		}
		codes = append(codes, CPVCode{
			Code:        code,
			Description: description,
		})
	}
	return codes
}

// buyerAddress reads the buyer's name and address, one line each, leaving
// out the "View profile" link.
func buyerAddress(value *html.Node) []string {
	var address []string
	for _, line := range lines(value) {
		if line != "View profile" {
			address = append(address, line)
		}
	}
	return address
}