package wiki

import (
	"fmt"
	"net/url"
	"regexp"
	"strconv"
	"strings"
)

// RS3ExchangeItem holds metadata parsed from a Module:Exchange/<name> page.
type RS3ExchangeItem struct {
	ItemID   int
	Name     string
	Value    int
	Limit    int
	Members  bool
	Category string
	Examine  string
}

// revisionResponse matches the JSON from action=query&prop=revisions&rvslots=main.
type revisionResponse struct {
	Query struct {
		Pages map[string]struct {
			PageID    int    `json:"pageid"`
			Title     string `json:"title"`
			Revisions []struct {
				Slots struct {
					Main struct {
						Content string `json:"*"`
					} `json:"main"`
				} `json:"slots"`
			} `json:"revisions"`
		} `json:"pages"`
	} `json:"query"`
}

// GetExchangeModule fetches Module:Exchange/<name> and parses item metadata.
// Returns nil, nil if the module page does not exist (item not tradeable).
func (c *Client) GetExchangeModule(itemName string) (*RS3ExchangeItem, error) {
	title := "Module:Exchange/" + itemName

	params := url.Values{
		"action":  {"query"},
		"titles":  {title},
		"prop":    {"revisions"},
		"rvprop":  {"content"},
		"rvslots": {"main"},
	}

	var resp revisionResponse
	if err := c.get(params, &resp); err != nil {
		return nil, fmt.Errorf("fetching exchange module: %w", err)
	}

	for id, page := range resp.Query.Pages {
		// Page ID -1 means the page doesn't exist
		if id == "-1" {
			return nil, nil
		}
		if len(page.Revisions) == 0 {
			return nil, nil
		}

		content := page.Revisions[0].Slots.Main.Content
		return parseLuaModule(content), nil
	}

	return nil, nil
}

var (
	reItemID   = regexp.MustCompile(`itemId\s*=\s*(\d+)`)
	reItem     = regexp.MustCompile(`item\s*=\s*'((?:[^'\\]|\\.)*)'`)
	reValue    = regexp.MustCompile(`value\s*=\s*(\d+)`)
	reLimit    = regexp.MustCompile(`limit\s*=\s*(\d+)`)
	reMembers  = regexp.MustCompile(`members\s*=\s*(true|false)`)
	reCategory = regexp.MustCompile(`category\s*=\s*'((?:[^'\\]|\\.)*)'`)
	reExamine  = regexp.MustCompile(`examine\s*=\s*'((?:[^'\\]|\\.)*)'`)
)

func parseLuaModule(content string) *RS3ExchangeItem {
	item := &RS3ExchangeItem{}

	if m := reItemID.FindStringSubmatch(content); m != nil {
		item.ItemID, _ = strconv.Atoi(m[1])
	}
	if m := reItem.FindStringSubmatch(content); m != nil {
		item.Name = unescapeLua(m[1])
	}
	if m := reValue.FindStringSubmatch(content); m != nil {
		item.Value, _ = strconv.Atoi(m[1])
	}
	if m := reLimit.FindStringSubmatch(content); m != nil {
		item.Limit, _ = strconv.Atoi(m[1])
	}
	if m := reMembers.FindStringSubmatch(content); m != nil {
		item.Members = strings.ToLower(m[1]) == "true"
	}
	if m := reCategory.FindStringSubmatch(content); m != nil {
		item.Category = unescapeLua(m[1])
	}
	if m := reExamine.FindStringSubmatch(content); m != nil {
		item.Examine = unescapeLua(m[1])
	}

	return item
}

// unescapeLua handles Lua string escape sequences in single-quoted strings.
func unescapeLua(s string) string {
	return strings.NewReplacer(`\'`, `'`, `\\`, `\`).Replace(s)
}