How to convert txt into html format using shell/bash

I have below data in a text file:

Details_A
name: A1
Valid: A1_Value
name: A2
Valid: A2_Value
Details_A2
name: A2
Valid: A2_Value
name: A2
Valid: A2_Value

which I am trying to convert into in below html table:

Details

You can use awk like this :

awk 'BEGIN { 
        x = 0;
        print "<table border="1">"
    }
    {
        if (NF == 1){
            print "<tr ><td colspan="2">"$i"</td>";
            print "</tr>"
        } else {
            if (x == 0){
                x++;
                print "<tr><td>"$i"</td>"
            } else {
                x = 0;
                print "<td>"$i"</td></tr>"
            }
        }
    }
    END {
        print "</table>"
    }' input.txt > table.html

Feel free to add any additional style

For older version of awk, you can use the following, tested on an awk implementation of 2009-11-26 (from one-true-awk) :

awk  'BEGIN {
        x = 0;
        y = 0;
        print "<table border="1">"
    }
    {
        for (i = 1; i<=NF ; i++){

            if (NF == 1){
                print "<tr ><td colspan="2">"$i"</td></tr>";
            } else {

                if (x == 0 && y == 0){
                    print "<tr><td>"$i" ";
                    x++;
                }
                else if (x == 0 && y == 1){
                    print "<td>"$i" ";
                    x++;
                }
                else if (x==(NF-1)){
                    x = 0;
                    y++;
                    if (y == 2){
                        y = 0;
                        print ""$i"</td></tr>";
                    }
                    else{
                        print ""$i"</td>";
                    }
                }
                else {
                    print ""$i" ";
                    x++;
                }
            }
        }
    }
    END {
        print "</table>"
    }' input.txt > table.html

For this last version, x is incremented at each space delimiter until we reach NF-1 which is the last word and we should put an ending </td>. The decision for the ending </tr> depends on the value of y which is incremented at each line and re-initialized when the max count of <td> is reached (here 2 <td> per <tr>)