I bet that was a linear power supply too. Then you just have a transient filter, transformer, rectifier, secondary filter. Someone posted an antique calculator a few days ago with a linear PSU, you could see it was just a transformer, schottky rectifier, capacitor, and a couple resistors.
Modern switch mode power supplies are to linear power supplies as a Core i7 is to an abacus.
You have to take the current from the lines, filter it with coils and a couple types of capacitor, plus a MOV for surges and an NTC thermistor for current inrush, rectify your current to DC, run it through a boost circuit as PFC pushing it up to 400V, then a pair of transistors switching on and off forces the polarity of the current to reverse several thousand times a second (there are about a dozen "topologies" for this stage), making an alternating current, which then passes through a transformer, and the current is then split into different paths and rectified into DC, which is then run through a magnetic amplifier to regulate the voltage (sometimes +5V and +3.3V are VRM regulated from the +12V; other times +5V and +12V share the same mag amp), then run through capacitors to filter, then into the wires.
All that disregarding powering the controller PCBs for the primary switchers, secondary, and PFC circuit, and the separate +5VSB power supply inside the PSU, plus the protections circuitry implementation, and a million niggling engineering details.
Computer PSUs are insane.